Central Heating Issue - Hot Water but no Central Heating

14 Oct 2015
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United Kingdom
Hi Guys,

I have an interesting problem that I'd like some ideas on. Here's the problem:

Hot water isnt a problem and comes on and off as per the timer however central heating is an issue. When the timer turns the central heating on nothing happens. No pump, no valve and no boiler.

The only way I can get the pump running and value to open for the central heating is to have the hot water on all the time.

Other than the system being off for the summer nothing has changed and I could independently turn on hot water or central heating or both.

Any thoughts would be appreciated

Thanks in advance
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Sounds like a faulty valve. Do you have one or two valves? What make and model is your programmer. If it is a honeywell st9400c then it could be faulty
I believe the valve is working fine. I can see it move on and off when the central heating is changed. I have a single value which is controlled by a Siemens RWB9. Thanks for your help.
The valve may be moving, but it is probably not triggering the microswitch when in the heating only position. What make of valve is it?

You will need a multimeter and a bit of electrical knowledge to test it.
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It's a British Gas job - BGMVSP-23

I'll take the cover off and check to see it power is getting to the micro switch. Will I need to replace the whole unit if the switch has failed?

Thanks again
On heating only. You should have power to white and grey wires on valve. When the valve opens and the microswitch activates, the orange wire should then become live. If the orange wire doesn't become live. And the grey and white wires are live, you need a new head. The blue bg valves are made By drayton. So replace the head for a ma1 drayton. Also check that the spindle on the valve body moves freely when you turn it with your fingers
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