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Feb 20, 2019
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G'Day fellers. Appreciate your help please:

When my boiler fires up it heats the water and radiators regardless of what is selected. I'm guessing that this means the valve is not moving from the de-energised position?

Its a Honeywell V4073A. The manual/auto lever moves freely both ways and will not latch in the man position. A test I found which involves turning the heating (only) on, holding the lever on manual then turning water on to check the valve motors across, did nothing.

A quick look under the cover shows the springs are OK and no sign of burning. The system was drained and refilled 6 years ago.

Over to you!
 
Last edited:
G'Day fellers. Appreciate your help please:

When my boiler fires up it heats the water and radiators regardless of what is selected. I'm guessing that this means the valve is not moving from the de-energised position?

Its a Honeywell V4073A. The manual/auto lever moves freely both ways and will not latch in the man position. A test I found which involves turning the heating (only) on, holding the lever on manual then turning water on to check the valve motors did nothing.

A quick look under the cover shows the springs are OK and no sign of burning. The system was drained and refilled 6 years ago.

Over to you!

When you turn the power off at the Heating isolation, does it close?

How competent at Electrical work are you?
Do you have a multimeter and know how to use it?
 
No it doesn't.
Basic but safe. I'd be happy to replace a powerhead or a synchronous motor
No I don’t.....

Here’s something that may be relevant:
All the pipes are now cool but the unit itself is still quite hot!
 
Last edited:
Associated system drain? Are you asking if you can get away with just changing the head?? I would do the lot.
 
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I would power off, test that it's off (pull a fuse and use a voltage tester). Remove the motor and check it over. They are normally fairly stiff to turn the cog beneath but will move. if it's jammed, replace it. They can be bought from DIY stores and are fairly cheap.
It could well be the head or valve but it is worth checking the condition of the motor first.
 
Remove the motor and check it over. They are normally fairly stiff to turn the cog beneath but will move. if it's jammed, replace it.

Ok, so remove the motor and see if the spindle can rotate:

If it doesnt, buy a new one. If it does, assume a problem with the electrical supply?

Anyone worried by the housing being hot when the pipes are cold? Would this indicate a motor trying and failing to move the valve? Wouldnt this just burn out the motor?
 
Ok, so remove the motor and see if the spindle can rotate:

If it doesnt, buy a new one. If it does, assume a problem with the electrical supply?

Anyone worried by the housing being hot when the pipes are cold? Would this indicate a motor trying and failing to move the valve? Wouldnt this just burn out the motor?
It will do that if the motor is stuck. Eventually it would burn out.
 
Wouldnt this just burn out the motor?
I don't think so. The earlier either/or valve (W-plan) definitely wouldn't, the motor stalled in the CH position, and it could stay that way all day. It dissipates about 5 watt in that condition.
I'm not 100% about the mid-position valve, but I think it probably does the same when CH only is calling. Wiring diagrams for both attached, if you want to try to work it out.
 

Attachments

That is the plan IF the valve is faulty.
Thats why I’m trying to diagnose first.
As mentioned, if its just the motor or powerhead, i could do it myself.
If you are getting a pro in. There is no need to diagnose. He will do his own fault finding even if you tell him it is the valve.
 
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Reactions: 1 person

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