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If it’s the other way round, and the 2-port valve controlling the hot water circuit is failing, it may be less obvious. The heating circuit valve may be open for long periods telling the boiler to fire. If the hot water valve is partially open, you may not run out of hot water. When a demand comes from the programmer (via the thermostat), the motor is energised and drives the valve open to allow water to pass. When the valve is fully open, a microswitch is operated in the powerhead, connecting the grey wire to the orange wire. This is called closing the switch. It sounds a bit counter-intuitive, but when a switch is closed it is completing the circuit and allowing current to pass; when the switch is opened it is opening a break in the circuit and stops current from passing. V4043C1156 is a 2 port, ½” BSP Female threaded, 3-wire, normally-closed zone valve but has no end switch A programmer and room thermostat (stat) are used to control heating times and room air temperatures. The programmer and room stat may be combined into a single programmable room stat.
The wires to disconnect are the two wires which run from the motor. On earlier motorised valves, these were both joined to other wires using metal crimps encased in plastic. On more recent valves, one wire is joined with a crimp and the other is wired directly to the electrical components of the valve. The commonest fault with Honeywell motorised valves is motor failure. Honeywell valve motor fault? Testing a Synchron valve motor Honeywell V4044C1288 22mm 3-port diverter valve. This valve is not a mid-position valve. It opens either Port A or Port B (usually heating and hot water). Apart from the few moments when it is switching between ports, Port A and Port B are not open together. Note that it is a 3-wire valve, not a 5-wire valve Both of these genuine SYNCHRON motors work in Honeywell motorised valves. The motors SYNCHRON make specifically for Honeywell come with two blue wires
This can be difficult to feel for at first. It is most obvious when the valve has been in the Heating Only position and reverts to the mid-position. The V4043B valves are uncommon and likely to be found in solid fuel systems. These valves fail-safe in the open position in the event of a power failure or valve motor failure. That noise and that bump are diagnostic. They tell us that the valve has moved into the mid-position where both Heating and Hot Water ports are open. If you can make a Honeywell 3-port mid-position valve move into all three of those positions, the valve and controls appear to be wired correctly and the valve appears to be working normally. The V4043 series of 2 port Motorised Valves has a wide range of flow control applications in domestic and light commercial central heating systems. The V4043H normally closed models have end switches for electrical control of pump and/or boiler.
The auxiliary circuit allows several 2-port motorised valves to be used to control separate zones without interacting electrically. Otherwise, if several zone valves were used without auxiliary circuits, and all were connected to the same pump so that the Live wire that opened each valve also fed the pump Live, there would be problems. The Honeywell V4073A 3-port valve has five wires. These are blue, green/yellow, white, grey and orange. Note that the grey and orange wires are used differently from the grey and orange wires of the 2-port valve! If you know how to work safely with mains voltage electricity, the valve motor can be tested with a multimeter. With the mains electrical supply turned off and isolated, the resistance across the two motor wires (either both blue or both orange) can be tested. To test correctly, at least one of the two motor wires must be disconnected from the heating wiring circuit. If, for example, the heating valve is failing in this way, you will get heat round the radiators while the cylinder hot water is being heated too. When the cylinder is up to temperature, the hot water motorised valve closes and no longer tells the boiler to fire, so the heating now stops too.If Hot Water is then satisfied (either by the programmer or cylinder stat), the grey wire is energised. As there is still a demand for Heating, the valve will motor to the Heating Only position (port A open; port B closed) and switch a 230V supply onto the orange wire, to power the boiler. The blue wire is the Neutral, N. The green/yellow wire is the Earth wire, E. The white wire is connected to the wire from the room thermostat which calls for heating (radiators or underfloor). The grey wire is used to drive the valve to the Water Off position, in which only the heating port A is open; it closes port B. The orange wire provides a Switched Live (Switched Line) feed to run the boiler and pump. Occasionally we come across a Honeywell motorised valve where the powerhead jams but the spindle (actuator shaft) is still free. Where this happens it is usually with the valve jammed open. If all the power to the central heating system is turned off, and the manual lever is still loose across the whole slot, the mechanism may be jammed.
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