Please can anyone help a DIY guy? ...CH problem....

tony mc said:

Thats the same as mine Tel but blown up and laminated so I can see the dam thing !

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Leesparkykent said:

With heating only selected on the programmer and the thermostat calling for heat the grey and white on the 3 port should both be live. White should be live as its connected to the thermostat which is calling for heat and programmer is on for heating. The grey should be live as the HW is selected to off on the programmer. If they are both live then the motor should turn the ball and arm within the valve body closing port B and making the orange live which then switches the boiler.

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vintageaxeman said:

Orange wire shows around 60v, white wire shows 240v.
That's on a NEW head and valve, sitting on the carpet. I presume that when you say 'confirm the orange wire becomes Live, that you mean 240v? But this CAN't be a faulty valve or head. This is the 3rd head I've tried....
Help much appreciated on this one.
By the way, I am loath to rewire (partly because the tails are all so short), but the honeywell wiring box is not done according to the printed or online Y-system wiring diagram...things are in a different order so it's really hard for a skilled amateur like me to follow....

Where do I go next with this please?

Remember that the valve appears to respond properly, the main issue is that the pump does not come on when heating is called for.

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mattg4321 said:

I had something similar recently. All wired correctly, valve was opening fully with 230v to white and grey but wasn't getting 230v on orange. Changed the head on the valve - same problem.

Called Honeywell to see if they could shed any light. Explained the problem and fairly quickly they said you need a capacitor between N and orange which they'd send out to me. Said DON'T fit anymore new heads as you will damage them without said capacitor. Mumbled something about pump overrun which I didn't catch and put the phone down!

Part arrived a couple of days later, fitted along with a new head and it all worked fine. Anyone else had this too?

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vintageaxeman said:

Good morning!

I have a problem with my central heating system…..and am wondering if anyone can help.

The system:

1. 15 year old detached house, with a 15 yr old Honeywell Y Plan CH system, which to all extents and purposes works FINE.

2. Boiler is a traditional ‘IDEAL Classic’ boiler, fitted inside the garage, wall mounted. Balanced flue.

3, Standard steel radiators, microbore plumbing. They all get hot very quickly when the system works properly.

4. Honeywell Y System, with a 3 way valve V4073A (28mm pipe) and pump, and hot water cylinder with a Honeywell cylinder thermostat, and the junction box for all the wiring, is all in the airing cupboard upstairs.

5. Downstairs in the hall there is a standard Honeywell Room thermostat. Model 6360B

6. Standard programmer, was a Honeywell ST6400, is now a Honeywell ST9400C, which times the hot water and heating separately.



Everything has worked fine until this summer. Normally I can set the programmer to Hot Water, or Heating, or Both….and it can be all automatic or I can just press the Extra Hour button on either.

What SHOULD happen of course is that when the electronics calls for heat, either for the hot water cylinder, or for the central heating, it will switch the 3-way diverter valve to the appropriate pipe and simultaneously switch the boiler and the pump on.

When I ask the system to heat up the hot water, everything works. Also, when I set the system to deliver hot water AND central heating at the same time, everything works fine….radiators get hot, hot water gets to temperature, etc.

BUT….My problem is this: When I ask the system to heat up the radiators ON THEIR OWN, the pump does not switch on, regardless of the setting on the room stat in the hall.


So far, I have tried the following:

1. Turned the electricity off and checked the tightness of all the wires in ALL the components and in the wiring centre. All tight and sound.

2. Replaced the valve actuator with a new replacement. In the process I checked whether the valve in the 3 way 28mm valve body was seized and it seems fine…. it swings from side to side perfectly as far as I can see, diverting the water to wherever it needs to go.

3. I then thought I had better check out the room thermostat in the hall, so I replaced it with a new one. NO CHANGE.

4. I then decided it MUST be the programer, so I bought a new direct replacement, but the current model. Fitted it to the existing baseplate, and it works like a charm on most settings, but STILL no heating without the hot water being on.

5. It CAN’T be the cylinder thermostat.

6. There is only one live cable going to the pump from the wiring centre, and I know the pump works, so it can’t be that.

7. I can’t imagine that the boiler has anything to do with it….It’s just switched on and off when there is a demand for heat….Surely it’s nothing there….?

8. So that just takes me back to the 3-way diverter valve…..could it possibly be that the swing of the actuator is not going far enough to hit limit switches and turn the pump on? So this morning I took the actuator head off and let it dangle free, set the system to ask for heating, HOPING that I would hear the sound of the pump…..but nothing.


Other than partially draining the system and replacing the whole diverter valve, (£75), I just dont know what to try next.


Any ideas? And thank you in advance for them!

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