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Honeywell Home 40003916-003/U Replacement Actuator Powerhead V4073A 3-Port Mid-Position 5-Wire Motorised Valve
Honeywell Home 40003916-003/U Replacement Actuator Powerhead V4073A 3-Port Mid-Position 5-Wire Motorised Valve
The Honeywell Home 40003916-003/U is the genuine replacement powerhead (actuator assembly) for Honeywell V4073A 3-port mid-position motorised valves — the standard 5-wire valve used in Y-plan central heating systems across the UK. When a V4073A head develops a fault — humming motor, stuck mid-position, failure to open or close, seized manual lever — this powerhead replaces the entire electrical and mechanical assembly without removing the valve body from the pipework and without draining the system (on post-1987 valves). Fitting requires only two screws and two locating pegs, takes around 30 minutes, and avoids the disruption and cost of a full valve replacement. Compatible with V4073A1039, V4073A1054, V4073A1062, and V4073A1088. 230V ~ 50Hz · 6W · 1m lead supplied. Spring-return operation. Maximum static pressure 8.6 bar. GTIN 5023220401476. 1-year manufacturer's warranty (Honeywell Home by Resideo).
⚠ Pre-1987 Valves Require an Additional Adaptor Kit — How to Check
V4073A valves made after 1987 can accept this powerhead directly, without draining — identified by a small circular bump on the top cover of the existing head and an OS suffix number of "6" or higher. Valves made before 1987 have a flat cover with no bump and use four screws (not two) to secure the head — these require the 40003918-007 adaptor kit (sold separately) before the 40003916-003 can be fitted. Fitting the new head to an old-style body without the adaptor kit will result in an insecure connection and potential water leakage. If in doubt, count the screws on the existing head: two screws = new style (no adaptor needed); four screws = old style (adaptor required).
V4073A valves made after 1987 can accept this powerhead directly, without draining — identified by a small circular bump on the top cover of the existing head and an OS suffix number of "6" or higher. Valves made before 1987 have a flat cover with no bump and use four screws (not two) to secure the head — these require the 40003918-007 adaptor kit (sold separately) before the 40003916-003 can be fitted. Fitting the new head to an old-style body without the adaptor kit will result in an insecure connection and potential water leakage. If in doubt, count the screws on the existing head: two screws = new style (no adaptor needed); four screws = old style (adaptor required).
⚠ Isolate Power Before Work — Qualified Electrician for Rewiring — Switch off all power supplies to the heating system before removing the existing head. Carefully note the position and colour of each existing wire before disconnecting. The wiring diagram in the installation instructions must be followed precisely — incorrect connection of the 5 wires can result in both heating and hot water firing simultaneously, neither zone operating, or damage to thermostats. Where the old head is a 6-wire type (pre-1990 installations with external relay), specific wiring changes are required — see the Honeywell installation guide (95C-10656).
V4073A
Mid-position valve
5-wire
Y-plan systems
No drain
Post-1987 valves
6W
Power consumption
8.6 bar
Max static pressure
Features & Benefits
✔ No System Drain — Post-1987 Direct Swap
On post-1987 V4073A valves (identified by the bump on the cover), the powerhead can be replaced without draining the heating system. The valve body remains in the pipework; the existing head is removed with two screws; the replacement head is fitted with the manual lever in the MAN. OPEN position to seat it correctly, secured with the two supplied screws, and wired back. This eliminates the disruption of draining, refilling, bleeding, and recommissioning the entire system — which on a pressurised sealed system can add an hour or more to what is otherwise a straightforward component swap. The system pressure is maintained throughout; only the actuator assembly is disturbed.
✔ Genuine Honeywell Part — OEM Quality
This is the genuine Honeywell Home (Resideo) replacement powerhead — manufactured by Pittway Sarl in Hungary to the same specification as the original factory-fitted head. The motor, microswitch assembly, spring-return mechanism, and manual lever are all OEM components. Using the genuine part ensures correct torque specification for the valve stem, correct microswitch switching points for the auxiliary switch output (which signals the boiler and pump), and the spring-return force matched to the V4073A body's flow characteristic. Third-party substitute heads may not match these parameters, risking intermittent operation or incomplete valve travel.
✔ Spring-Return Mid-Position Operation
The V4073A mid-position valve — and therefore this replacement head — uses spring-return action to deliver the valve's three operating states: hot water only (valve in HW port, spring holds the diverter closed to CH), mid-position (both HW and CH ports open — motor powered against spring), and central heating only (valve fully driven, HW port closed). The spring return ensures that on power loss, the valve defaults to the hot water position — a fail-safe behaviour built into Y-plan system design. The motor drives the valve against the spring to reach mid-position; the auxiliary microswitch fires when both circuits are satisfied by the boiler.
✔ Manual Lever — AUTO and MAN. OPEN Positions
The powerhead incorporates a manual override lever with two positions: AUTO (normal electrical operation) and MAN. OPEN (valve held physically open for drain-down or system filling). Moving the lever to MAN. OPEN allows water to flow through the valve regardless of whether the motor is powered — essential for filling a pressurised sealed system or bleeding the system after maintenance work. The lever must be returned to AUTO before normal operation resumes; leaving it in MAN. OPEN will bypass all thermostat control. During the head replacement procedure, the lever is placed in MAN. OPEN to allow the head to seat correctly on the valve body shaft.
✔ 1 Metre Pre-Wired Lead Supplied
The replacement head is supplied factory-wired with a 1 metre lead terminated in the standard 5-wire colour code used in UK Y-plan heating systems. The five conductors are: neutral (blue), live 230V in (brown), orange (HW demand — drives motor to mid-position), white (CH demand — drives motor fully open), grey (auxiliary switch output — fires boiler and pump). The supplied lead length is sufficient for most installations where the junction box is located adjacent to the valve; where longer runs are needed, the existing junction box wiring is retained and only the short tail from head to junction box is replaced.
✔ Save vs Full Valve Replacement
When a V4073A motorised valve fails, the instinctive response is often to replace the entire valve — body, connections, and all. In the majority of cases, only the powerhead has failed: the valve body, seats, and pipework connections are sound and have decades of remaining service life. Replacing only the powerhead with this genuine part avoids cutting into the pipework, replacing compression fittings or solder joints, and the associated risk of joint failure after reassembly. The cost and labour saving over a full valve replacement is significant, and the result is functionally identical — the same new motor and microswitch assembly is installed in either case.
Compatible V4073A Valve Models
| Valve Model | Notes | Adaptor Required? |
|---|---|---|
| V4073A1039 | Post-1987 — bump visible on cover | No — direct fit |
| V4073A1054 | Post-1987 — bump visible on cover | No — direct fit |
| V4073A1062 | Post-1987 — bump visible on cover | No — direct fit |
| V4073A1088 | Post-1987 — bump visible on cover | No — direct fit |
| Pre-1987 V4073 (OS suffix <6, no bump, 4 screws) | Flat cover, four-screw attachment | Yes — 40003918-007 adaptor kit required |
Technical Specifications — 40003916-003/U
| Manufacturer / MPN | Honeywell Home (by Resideo) — 40003916-003/U |
| GTIN | 5023220401476 |
| Application | Replacement powerhead for V4073A 3-port mid-position motorised valves — 5-wire Y-plan systems |
| Power Supply | 230V ~ 50Hz |
| Power Consumption | 6W |
| Lead Supplied | 1 metre — 5-wire colour-coded |
| Valve Operation | Spring-return — mid-position (3-port) |
| Max. Load (Inductive) | 2.2A |
| Max. Load (Resistive) | 2.2A |
| Max. Static Pressure | 8.6 bar |
| Operating Temperature Range | +5°C to +88°C (fluid) |
| Max. Ambient Temperature | +52°C |
| Manual Override | Yes — AUTO / MAN. OPEN lever |
| Fixing Method | 2 screws + 2 locating pegs (new-style bodies) |
| Gross Weight (inc. packaging) | 0.522 kg |
| Country of Origin | Hungary (manufactured by Pittway Sarl for European region) |
| British Gas Reference | 378454 |
| Warranty | 1 year — Honeywell Home manufacturer's warranty |
Frequently Asked Questions
What is the difference between the "-003" and "-001" suffix — can I use "-001" on a 3-port valve?
No — the suffix matters. The 40003916-003/U is the 5-wire head for the V4073A mid-position (3-port) valve used in Y-plan systems — it contains the motor, spring, and microswitch wired for both heating and hot water demand signals plus the auxiliary boiler output. The 40003916-001 is the 2-wire head for 2-port zone valves (V4043/V4044 series) used in S-plan systems — different internal wiring, different microswitch function, different mechanical travel. Fitting a "-001" head to a 3-port body, or vice versa, will result in incorrect valve function and potential wiring damage.
My valve is humming but not moving — is the powerhead definitely the cause?
A continuous hum with no valve movement is a strong indicator of a motor winding failure or seized motor — typically the powerhead. However, before replacing, it is worth checking: (1) the manual lever — if it has been left in MAN. OPEN, the valve won't respond to electrical signals; (2) the wiring connections — a loose or corroded terminal can cause erratic behaviour; (3) the valve body itself — in rare cases the spindle can seize in the body rather than the motor failing. To test the body independently, move the manual lever to MAN. OPEN and check if water flows through the correct port. If the body appears free and the wiring is sound, the powerhead is almost certainly the fault. Replacing the powerhead first is the correct diagnostic step before considering full valve replacement.
After fitting, my central heating and hot water both come on together — what's wrong?
This is the most common post-installation symptom and is almost always a wiring error, not a faulty head. The five wires from the valve connect to: neutral (blue), live (brown), hot water demand (orange — drives motor to mid-position), central heating demand (white — drives motor fully open), and auxiliary output (grey — fires the boiler/pump). If orange and white are swapped, both zones will fire simultaneously. Cross-reference your wiring against the Honeywell installation guide 95C-10656, paying particular attention to the auxiliary switch output on grey — this wire must only be connected once the valve reaches its end position. If replacing a 6-wire valve with an internal relay, specific additional wiring changes are required — the brown wire from the old relay is omitted and the cylinder thermostat C and 1 terminals must be reversed.
Do I need to isolate the boiler before replacing the head?
Yes — all electrical power to the heating system must be isolated before starting work. This means switching off at the programmer/time control, at the system's unswitched fused spur, or at the consumer unit's heating circuit. The valve operates at 230V and is connected to the wiring centre alongside the boiler, pump, and thermostats — live conductors are present in the junction box and at the valve terminals even when the heating is not actively calling. A shock from incorrectly isolated wiring at a junction box is a serious risk. Isolation must be confirmed with a voltage tester before any electrical connections are disturbed.
Can this head convert a 3-port diverter valve to a mid-position valve?
Yes — in principle. A 3-port diverter (V4043 body) and a 3-port mid-position valve (V4073A body) use a similar physical construction, and the 40003916-003 powerhead can be fitted to a V4043 body, converting it electrically from a diverter to a mid-position configuration. The full Y-plan wiring (5-wire: neutral, live, orange HW, white CH, grey auxiliary) must then be connected correctly. However, before doing this, confirm the V4043 body valve seats are compatible with mid-position operation — a diverter valve is designed to fully route flow to one port or the other, while a mid-position valve is designed to allow partial flow through both ports simultaneously. If the body seating is not designed for this, mid-position flow balance may not be correct. Consult the Honeywell installation guide and a qualified heating engineer before proceeding.
$53.85
Original: $153.86
-65%Honeywell Home 40003916-003/U Replacement Actuator Powerhead V4073A 3-Port Mid-Position 5-Wire Motorised Valve—
$153.86
$53.85More Images
Honeywell Home 40003916-003/U Replacement Actuator Powerhead V4073A 3-Port Mid-Position 5-Wire Motorised Valve
The Honeywell Home 40003916-003/U is the genuine replacement powerhead (actuator assembly) for Honeywell V4073A 3-port mid-position motorised valves — the standard 5-wire valve used in Y-plan central heating systems across the UK. When a V4073A head develops a fault — humming motor, stuck mid-position, failure to open or close, seized manual lever — this powerhead replaces the entire electrical and mechanical assembly without removing the valve body from the pipework and without draining the system (on post-1987 valves). Fitting requires only two screws and two locating pegs, takes around 30 minutes, and avoids the disruption and cost of a full valve replacement. Compatible with V4073A1039, V4073A1054, V4073A1062, and V4073A1088. 230V ~ 50Hz · 6W · 1m lead supplied. Spring-return operation. Maximum static pressure 8.6 bar. GTIN 5023220401476. 1-year manufacturer's warranty (Honeywell Home by Resideo).
⚠ Pre-1987 Valves Require an Additional Adaptor Kit — How to Check
V4073A valves made after 1987 can accept this powerhead directly, without draining — identified by a small circular bump on the top cover of the existing head and an OS suffix number of "6" or higher. Valves made before 1987 have a flat cover with no bump and use four screws (not two) to secure the head — these require the 40003918-007 adaptor kit (sold separately) before the 40003916-003 can be fitted. Fitting the new head to an old-style body without the adaptor kit will result in an insecure connection and potential water leakage. If in doubt, count the screws on the existing head: two screws = new style (no adaptor needed); four screws = old style (adaptor required).
V4073A valves made after 1987 can accept this powerhead directly, without draining — identified by a small circular bump on the top cover of the existing head and an OS suffix number of "6" or higher. Valves made before 1987 have a flat cover with no bump and use four screws (not two) to secure the head — these require the 40003918-007 adaptor kit (sold separately) before the 40003916-003 can be fitted. Fitting the new head to an old-style body without the adaptor kit will result in an insecure connection and potential water leakage. If in doubt, count the screws on the existing head: two screws = new style (no adaptor needed); four screws = old style (adaptor required).
⚠ Isolate Power Before Work — Qualified Electrician for Rewiring — Switch off all power supplies to the heating system before removing the existing head. Carefully note the position and colour of each existing wire before disconnecting. The wiring diagram in the installation instructions must be followed precisely — incorrect connection of the 5 wires can result in both heating and hot water firing simultaneously, neither zone operating, or damage to thermostats. Where the old head is a 6-wire type (pre-1990 installations with external relay), specific wiring changes are required — see the Honeywell installation guide (95C-10656).
V4073A
Mid-position valve
5-wire
Y-plan systems
No drain
Post-1987 valves
6W
Power consumption
8.6 bar
Max static pressure
Features & Benefits
✔ No System Drain — Post-1987 Direct Swap
On post-1987 V4073A valves (identified by the bump on the cover), the powerhead can be replaced without draining the heating system. The valve body remains in the pipework; the existing head is removed with two screws; the replacement head is fitted with the manual lever in the MAN. OPEN position to seat it correctly, secured with the two supplied screws, and wired back. This eliminates the disruption of draining, refilling, bleeding, and recommissioning the entire system — which on a pressurised sealed system can add an hour or more to what is otherwise a straightforward component swap. The system pressure is maintained throughout; only the actuator assembly is disturbed.
✔ Genuine Honeywell Part — OEM Quality
This is the genuine Honeywell Home (Resideo) replacement powerhead — manufactured by Pittway Sarl in Hungary to the same specification as the original factory-fitted head. The motor, microswitch assembly, spring-return mechanism, and manual lever are all OEM components. Using the genuine part ensures correct torque specification for the valve stem, correct microswitch switching points for the auxiliary switch output (which signals the boiler and pump), and the spring-return force matched to the V4073A body's flow characteristic. Third-party substitute heads may not match these parameters, risking intermittent operation or incomplete valve travel.
✔ Spring-Return Mid-Position Operation
The V4073A mid-position valve — and therefore this replacement head — uses spring-return action to deliver the valve's three operating states: hot water only (valve in HW port, spring holds the diverter closed to CH), mid-position (both HW and CH ports open — motor powered against spring), and central heating only (valve fully driven, HW port closed). The spring return ensures that on power loss, the valve defaults to the hot water position — a fail-safe behaviour built into Y-plan system design. The motor drives the valve against the spring to reach mid-position; the auxiliary microswitch fires when both circuits are satisfied by the boiler.
✔ Manual Lever — AUTO and MAN. OPEN Positions
The powerhead incorporates a manual override lever with two positions: AUTO (normal electrical operation) and MAN. OPEN (valve held physically open for drain-down or system filling). Moving the lever to MAN. OPEN allows water to flow through the valve regardless of whether the motor is powered — essential for filling a pressurised sealed system or bleeding the system after maintenance work. The lever must be returned to AUTO before normal operation resumes; leaving it in MAN. OPEN will bypass all thermostat control. During the head replacement procedure, the lever is placed in MAN. OPEN to allow the head to seat correctly on the valve body shaft.
✔ 1 Metre Pre-Wired Lead Supplied
The replacement head is supplied factory-wired with a 1 metre lead terminated in the standard 5-wire colour code used in UK Y-plan heating systems. The five conductors are: neutral (blue), live 230V in (brown), orange (HW demand — drives motor to mid-position), white (CH demand — drives motor fully open), grey (auxiliary switch output — fires boiler and pump). The supplied lead length is sufficient for most installations where the junction box is located adjacent to the valve; where longer runs are needed, the existing junction box wiring is retained and only the short tail from head to junction box is replaced.
✔ Save vs Full Valve Replacement
When a V4073A motorised valve fails, the instinctive response is often to replace the entire valve — body, connections, and all. In the majority of cases, only the powerhead has failed: the valve body, seats, and pipework connections are sound and have decades of remaining service life. Replacing only the powerhead with this genuine part avoids cutting into the pipework, replacing compression fittings or solder joints, and the associated risk of joint failure after reassembly. The cost and labour saving over a full valve replacement is significant, and the result is functionally identical — the same new motor and microswitch assembly is installed in either case.
Compatible V4073A Valve Models
| Valve Model | Notes | Adaptor Required? |
|---|---|---|
| V4073A1039 | Post-1987 — bump visible on cover | No — direct fit |
| V4073A1054 | Post-1987 — bump visible on cover | No — direct fit |
| V4073A1062 | Post-1987 — bump visible on cover | No — direct fit |
| V4073A1088 | Post-1987 — bump visible on cover | No — direct fit |
| Pre-1987 V4073 (OS suffix <6, no bump, 4 screws) | Flat cover, four-screw attachment | Yes — 40003918-007 adaptor kit required |
Technical Specifications — 40003916-003/U
| Manufacturer / MPN | Honeywell Home (by Resideo) — 40003916-003/U |
| GTIN | 5023220401476 |
| Application | Replacement powerhead for V4073A 3-port mid-position motorised valves — 5-wire Y-plan systems |
| Power Supply | 230V ~ 50Hz |
| Power Consumption | 6W |
| Lead Supplied | 1 metre — 5-wire colour-coded |
| Valve Operation | Spring-return — mid-position (3-port) |
| Max. Load (Inductive) | 2.2A |
| Max. Load (Resistive) | 2.2A |
| Max. Static Pressure | 8.6 bar |
| Operating Temperature Range | +5°C to +88°C (fluid) |
| Max. Ambient Temperature | +52°C |
| Manual Override | Yes — AUTO / MAN. OPEN lever |
| Fixing Method | 2 screws + 2 locating pegs (new-style bodies) |
| Gross Weight (inc. packaging) | 0.522 kg |
| Country of Origin | Hungary (manufactured by Pittway Sarl for European region) |
| British Gas Reference | 378454 |
| Warranty | 1 year — Honeywell Home manufacturer's warranty |
Frequently Asked Questions
What is the difference between the "-003" and "-001" suffix — can I use "-001" on a 3-port valve?
No — the suffix matters. The 40003916-003/U is the 5-wire head for the V4073A mid-position (3-port) valve used in Y-plan systems — it contains the motor, spring, and microswitch wired for both heating and hot water demand signals plus the auxiliary boiler output. The 40003916-001 is the 2-wire head for 2-port zone valves (V4043/V4044 series) used in S-plan systems — different internal wiring, different microswitch function, different mechanical travel. Fitting a "-001" head to a 3-port body, or vice versa, will result in incorrect valve function and potential wiring damage.
My valve is humming but not moving — is the powerhead definitely the cause?
A continuous hum with no valve movement is a strong indicator of a motor winding failure or seized motor — typically the powerhead. However, before replacing, it is worth checking: (1) the manual lever — if it has been left in MAN. OPEN, the valve won't respond to electrical signals; (2) the wiring connections — a loose or corroded terminal can cause erratic behaviour; (3) the valve body itself — in rare cases the spindle can seize in the body rather than the motor failing. To test the body independently, move the manual lever to MAN. OPEN and check if water flows through the correct port. If the body appears free and the wiring is sound, the powerhead is almost certainly the fault. Replacing the powerhead first is the correct diagnostic step before considering full valve replacement.
After fitting, my central heating and hot water both come on together — what's wrong?
This is the most common post-installation symptom and is almost always a wiring error, not a faulty head. The five wires from the valve connect to: neutral (blue), live (brown), hot water demand (orange — drives motor to mid-position), central heating demand (white — drives motor fully open), and auxiliary output (grey — fires the boiler/pump). If orange and white are swapped, both zones will fire simultaneously. Cross-reference your wiring against the Honeywell installation guide 95C-10656, paying particular attention to the auxiliary switch output on grey — this wire must only be connected once the valve reaches its end position. If replacing a 6-wire valve with an internal relay, specific additional wiring changes are required — the brown wire from the old relay is omitted and the cylinder thermostat C and 1 terminals must be reversed.
Do I need to isolate the boiler before replacing the head?
Yes — all electrical power to the heating system must be isolated before starting work. This means switching off at the programmer/time control, at the system's unswitched fused spur, or at the consumer unit's heating circuit. The valve operates at 230V and is connected to the wiring centre alongside the boiler, pump, and thermostats — live conductors are present in the junction box and at the valve terminals even when the heating is not actively calling. A shock from incorrectly isolated wiring at a junction box is a serious risk. Isolation must be confirmed with a voltage tester before any electrical connections are disturbed.
Can this head convert a 3-port diverter valve to a mid-position valve?
Yes — in principle. A 3-port diverter (V4043 body) and a 3-port mid-position valve (V4073A body) use a similar physical construction, and the 40003916-003 powerhead can be fitted to a V4043 body, converting it electrically from a diverter to a mid-position configuration. The full Y-plan wiring (5-wire: neutral, live, orange HW, white CH, grey auxiliary) must then be connected correctly. However, before doing this, confirm the V4043 body valve seats are compatible with mid-position operation — a diverter valve is designed to fully route flow to one port or the other, while a mid-position valve is designed to allow partial flow through both ports simultaneously. If the body seating is not designed for this, mid-position flow balance may not be correct. Consult the Honeywell installation guide and a qualified heating engineer before proceeding.
Product Information
Product Information
Shipping & Returns
Shipping & Returns
Description
The Honeywell Home 40003916-003/U is the genuine replacement powerhead (actuator assembly) for Honeywell V4073A 3-port mid-position motorised valves — the standard 5-wire valve used in Y-plan central heating systems across the UK. When a V4073A head develops a fault — humming motor, stuck mid-position, failure to open or close, seized manual lever — this powerhead replaces the entire electrical and mechanical assembly without removing the valve body from the pipework and without draining the system (on post-1987 valves). Fitting requires only two screws and two locating pegs, takes around 30 minutes, and avoids the disruption and cost of a full valve replacement. Compatible with V4073A1039, V4073A1054, V4073A1062, and V4073A1088. 230V ~ 50Hz · 6W · 1m lead supplied. Spring-return operation. Maximum static pressure 8.6 bar. GTIN 5023220401476. 1-year manufacturer's warranty (Honeywell Home by Resideo).
⚠ Pre-1987 Valves Require an Additional Adaptor Kit — How to Check
V4073A valves made after 1987 can accept this powerhead directly, without draining — identified by a small circular bump on the top cover of the existing head and an OS suffix number of "6" or higher. Valves made before 1987 have a flat cover with no bump and use four screws (not two) to secure the head — these require the 40003918-007 adaptor kit (sold separately) before the 40003916-003 can be fitted. Fitting the new head to an old-style body without the adaptor kit will result in an insecure connection and potential water leakage. If in doubt, count the screws on the existing head: two screws = new style (no adaptor needed); four screws = old style (adaptor required).
V4073A valves made after 1987 can accept this powerhead directly, without draining — identified by a small circular bump on the top cover of the existing head and an OS suffix number of "6" or higher. Valves made before 1987 have a flat cover with no bump and use four screws (not two) to secure the head — these require the 40003918-007 adaptor kit (sold separately) before the 40003916-003 can be fitted. Fitting the new head to an old-style body without the adaptor kit will result in an insecure connection and potential water leakage. If in doubt, count the screws on the existing head: two screws = new style (no adaptor needed); four screws = old style (adaptor required).
⚠ Isolate Power Before Work — Qualified Electrician for Rewiring — Switch off all power supplies to the heating system before removing the existing head. Carefully note the position and colour of each existing wire before disconnecting. The wiring diagram in the installation instructions must be followed precisely — incorrect connection of the 5 wires can result in both heating and hot water firing simultaneously, neither zone operating, or damage to thermostats. Where the old head is a 6-wire type (pre-1990 installations with external relay), specific wiring changes are required — see the Honeywell installation guide (95C-10656).
V4073A
Mid-position valve
5-wire
Y-plan systems
No drain
Post-1987 valves
6W
Power consumption
8.6 bar
Max static pressure
Features & Benefits
✔ No System Drain — Post-1987 Direct Swap
On post-1987 V4073A valves (identified by the bump on the cover), the powerhead can be replaced without draining the heating system. The valve body remains in the pipework; the existing head is removed with two screws; the replacement head is fitted with the manual lever in the MAN. OPEN position to seat it correctly, secured with the two supplied screws, and wired back. This eliminates the disruption of draining, refilling, bleeding, and recommissioning the entire system — which on a pressurised sealed system can add an hour or more to what is otherwise a straightforward component swap. The system pressure is maintained throughout; only the actuator assembly is disturbed.
✔ Genuine Honeywell Part — OEM Quality
This is the genuine Honeywell Home (Resideo) replacement powerhead — manufactured by Pittway Sarl in Hungary to the same specification as the original factory-fitted head. The motor, microswitch assembly, spring-return mechanism, and manual lever are all OEM components. Using the genuine part ensures correct torque specification for the valve stem, correct microswitch switching points for the auxiliary switch output (which signals the boiler and pump), and the spring-return force matched to the V4073A body's flow characteristic. Third-party substitute heads may not match these parameters, risking intermittent operation or incomplete valve travel.
✔ Spring-Return Mid-Position Operation
The V4073A mid-position valve — and therefore this replacement head — uses spring-return action to deliver the valve's three operating states: hot water only (valve in HW port, spring holds the diverter closed to CH), mid-position (both HW and CH ports open — motor powered against spring), and central heating only (valve fully driven, HW port closed). The spring return ensures that on power loss, the valve defaults to the hot water position — a fail-safe behaviour built into Y-plan system design. The motor drives the valve against the spring to reach mid-position; the auxiliary microswitch fires when both circuits are satisfied by the boiler.
✔ Manual Lever — AUTO and MAN. OPEN Positions
The powerhead incorporates a manual override lever with two positions: AUTO (normal electrical operation) and MAN. OPEN (valve held physically open for drain-down or system filling). Moving the lever to MAN. OPEN allows water to flow through the valve regardless of whether the motor is powered — essential for filling a pressurised sealed system or bleeding the system after maintenance work. The lever must be returned to AUTO before normal operation resumes; leaving it in MAN. OPEN will bypass all thermostat control. During the head replacement procedure, the lever is placed in MAN. OPEN to allow the head to seat correctly on the valve body shaft.
✔ 1 Metre Pre-Wired Lead Supplied
The replacement head is supplied factory-wired with a 1 metre lead terminated in the standard 5-wire colour code used in UK Y-plan heating systems. The five conductors are: neutral (blue), live 230V in (brown), orange (HW demand — drives motor to mid-position), white (CH demand — drives motor fully open), grey (auxiliary switch output — fires boiler and pump). The supplied lead length is sufficient for most installations where the junction box is located adjacent to the valve; where longer runs are needed, the existing junction box wiring is retained and only the short tail from head to junction box is replaced.
✔ Save vs Full Valve Replacement
When a V4073A motorised valve fails, the instinctive response is often to replace the entire valve — body, connections, and all. In the majority of cases, only the powerhead has failed: the valve body, seats, and pipework connections are sound and have decades of remaining service life. Replacing only the powerhead with this genuine part avoids cutting into the pipework, replacing compression fittings or solder joints, and the associated risk of joint failure after reassembly. The cost and labour saving over a full valve replacement is significant, and the result is functionally identical — the same new motor and microswitch assembly is installed in either case.
Compatible V4073A Valve Models
| Valve Model | Notes | Adaptor Required? |
|---|---|---|
| V4073A1039 | Post-1987 — bump visible on cover | No — direct fit |
| V4073A1054 | Post-1987 — bump visible on cover | No — direct fit |
| V4073A1062 | Post-1987 — bump visible on cover | No — direct fit |
| V4073A1088 | Post-1987 — bump visible on cover | No — direct fit |
| Pre-1987 V4073 (OS suffix <6, no bump, 4 screws) | Flat cover, four-screw attachment | Yes — 40003918-007 adaptor kit required |
Technical Specifications — 40003916-003/U
| Manufacturer / MPN | Honeywell Home (by Resideo) — 40003916-003/U |
| GTIN | 5023220401476 |
| Application | Replacement powerhead for V4073A 3-port mid-position motorised valves — 5-wire Y-plan systems |
| Power Supply | 230V ~ 50Hz |
| Power Consumption | 6W |
| Lead Supplied | 1 metre — 5-wire colour-coded |
| Valve Operation | Spring-return — mid-position (3-port) |
| Max. Load (Inductive) | 2.2A |
| Max. Load (Resistive) | 2.2A |
| Max. Static Pressure | 8.6 bar |
| Operating Temperature Range | +5°C to +88°C (fluid) |
| Max. Ambient Temperature | +52°C |
| Manual Override | Yes — AUTO / MAN. OPEN lever |
| Fixing Method | 2 screws + 2 locating pegs (new-style bodies) |
| Gross Weight (inc. packaging) | 0.522 kg |
| Country of Origin | Hungary (manufactured by Pittway Sarl for European region) |
| British Gas Reference | 378454 |
| Warranty | 1 year — Honeywell Home manufacturer's warranty |
Frequently Asked Questions
What is the difference between the "-003" and "-001" suffix — can I use "-001" on a 3-port valve?
No — the suffix matters. The 40003916-003/U is the 5-wire head for the V4073A mid-position (3-port) valve used in Y-plan systems — it contains the motor, spring, and microswitch wired for both heating and hot water demand signals plus the auxiliary boiler output. The 40003916-001 is the 2-wire head for 2-port zone valves (V4043/V4044 series) used in S-plan systems — different internal wiring, different microswitch function, different mechanical travel. Fitting a "-001" head to a 3-port body, or vice versa, will result in incorrect valve function and potential wiring damage.
My valve is humming but not moving — is the powerhead definitely the cause?
A continuous hum with no valve movement is a strong indicator of a motor winding failure or seized motor — typically the powerhead. However, before replacing, it is worth checking: (1) the manual lever — if it has been left in MAN. OPEN, the valve won't respond to electrical signals; (2) the wiring connections — a loose or corroded terminal can cause erratic behaviour; (3) the valve body itself — in rare cases the spindle can seize in the body rather than the motor failing. To test the body independently, move the manual lever to MAN. OPEN and check if water flows through the correct port. If the body appears free and the wiring is sound, the powerhead is almost certainly the fault. Replacing the powerhead first is the correct diagnostic step before considering full valve replacement.
After fitting, my central heating and hot water both come on together — what's wrong?
This is the most common post-installation symptom and is almost always a wiring error, not a faulty head. The five wires from the valve connect to: neutral (blue), live (brown), hot water demand (orange — drives motor to mid-position), central heating demand (white — drives motor fully open), and auxiliary output (grey — fires the boiler/pump). If orange and white are swapped, both zones will fire simultaneously. Cross-reference your wiring against the Honeywell installation guide 95C-10656, paying particular attention to the auxiliary switch output on grey — this wire must only be connected once the valve reaches its end position. If replacing a 6-wire valve with an internal relay, specific additional wiring changes are required — the brown wire from the old relay is omitted and the cylinder thermostat C and 1 terminals must be reversed.
Do I need to isolate the boiler before replacing the head?
Yes — all electrical power to the heating system must be isolated before starting work. This means switching off at the programmer/time control, at the system's unswitched fused spur, or at the consumer unit's heating circuit. The valve operates at 230V and is connected to the wiring centre alongside the boiler, pump, and thermostats — live conductors are present in the junction box and at the valve terminals even when the heating is not actively calling. A shock from incorrectly isolated wiring at a junction box is a serious risk. Isolation must be confirmed with a voltage tester before any electrical connections are disturbed.
Can this head convert a 3-port diverter valve to a mid-position valve?
Yes — in principle. A 3-port diverter (V4043 body) and a 3-port mid-position valve (V4073A body) use a similar physical construction, and the 40003916-003 powerhead can be fitted to a V4043 body, converting it electrically from a diverter to a mid-position configuration. The full Y-plan wiring (5-wire: neutral, live, orange HW, white CH, grey auxiliary) must then be connected correctly. However, before doing this, confirm the V4043 body valve seats are compatible with mid-position operation — a diverter valve is designed to fully route flow to one port or the other, while a mid-position valve is designed to allow partial flow through both ports simultaneously. If the body seating is not designed for this, mid-position flow balance may not be correct. Consult the Honeywell installation guide and a qualified heating engineer before proceeding.
