BAXI BOILER NOT FIRING UP

Bal

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Mar 13, 2003, 12:30:07 PM3/13/03

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Been round to check the boiler at my mother's house and would appreciate any
diagnostic tips.
Model is an ancient BAXI WM531 being used in a gravity fed system.

There is a pilot light - so there is gas supply.
Controller works as far as switching on the central heating pump , turned
the thermostat on and off a couple off times but have been unable to get the
boiler to fire up. Please don't shout at me after reading the following but
to cancel out the thermostat being at fault I disconnected it and shorted
the wires - again no joy which to me indicates a problem elsewhere.

Any help would be greatly appreciated in recommend where else the problem
could lie.

Thanks in advance

Bal

Ed Sirett

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Mar 13, 2003, 2:25:43 PM3/13/03

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The problem lies somewhere between the wiring to the boiler, internal
wiring of the boiler or the gas valve.

I take it that when you say 'shorted' the thermostats you mean 'bridged'
i.e. you elimanated the t/stat as possible problem rather than short
circuited its output!

A simply continuity probe/ neon screwdriver should let you diagnose the
electrical problem.
A boiler of this age may well have a 240V-24V transformer - this may
have failed. If the terminals of the gas valve are unenclosed it is
almost certain it is 24V.

Does the gas valve make a clicking noise?
If the valve is getting the 24V or 230V to it then its clearly broken.

The valve is likely the best part of 100 quid + fitting so that may
inform you about what happens next.

HTH
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

BillP

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Mar 13, 2003, 4:05:33 PM3/13/03

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"Bal" <ne...@SPAMSPOILhavemore.info> wrote in message
news:3e70c01d$0$21999$cc9e...@news.dial.pipex.com...

Hi Bal.

I've got a Baxi WM381 and had this problem some time ago. The fault on mine
was failed gas valve solenoid. Yours of course maybe due to something else.

My boiler manual covers models WM281, WM381, and WM 532.

The WM531 may be very similar.

If you open the bottom hinged panel, can you see a set of operating
instructions stuck to the inside. On this should be a diagram of the
boiler's internal circuit. If it's like mine it's all 240v. Incoming live
goes to boiler thermostat, through this to the gas valve solenoid then back
to neutral. There is a suppressor across the solenoid.

If you can use a multi-meter you can trace the fault.

Set the central heating programmer to CH, turn the room stat full up. The
pump is now running.

Do you have 240v at the boiler terminals?
If NO fault is in wiring outside the boiler.
If YES fault is in the boiler.

If fault is in boiler, isolate boiler supply and with meter on ohms, check
continuity of all internal wiring. If wiring is ok then look for faulty
component.

Turn boiler supply back on. Set meter to back to AC volts.

Turn the boiler stat up to max. Do you have 240v at the gas valve?
If NO boiler thermostat is faulty.
If yes Gas valve solenoid is open circuit. (You could check this with supply
off and the meter set on ohms scale)

I could not buy a solenoid, I had to buy a gas valve assembly complete.

It is possible to just take the solenoids off the valves and swap them. The
solenoid is fixed to the valve with four Phillips head screws. (transfer the
solenoid with the new gasket).

You will need to set the burner pressure afterwards.

Don't do it if you're unsure.

Bal

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Mar 13, 2003, 6:12:20 PM3/13/03

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Many thanks for all your feedback guys. I can't risk too much downtime so
have called an engineer to pop in tomorrow morning.
Will report back with his findings.

thanks again

Bal

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Mar 14, 2003, 11:36:05 AM3/14/03

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all systems go - it was a faulty gas valve which was replaced by the repair
man at a cost of £75 all inclusive which I think is bloody reasonable.
I asked him to quote for a new boiler and this came in at boiler+300
fitting, reasonable?

thanks again

Bal

Ed Sirett

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Mar 14, 2003, 3:36:55 PM3/14/03

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Exceptionally so. The gas valves are of that sort of cost alone -
although this model might be very much cheaper.

geoff

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Mar 14, 2003, 6:23:15 PM3/14/03

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In message <3E723D67...@makewrite.demon.co.uk>, Ed Sirett
<e...@makewrite.demon.co.uk> writes

>Bal wrote:
>>
>> all systems go - it was a faulty gas valve which was replaced by the repair
>> man at a cost of £75 all inclusive which I think is bloody reasonable.
>> I asked him to quote for a new boiler and this came in at boiler+300
>> fitting, reasonable?
>>
>> thanks again
>>
>> Bal
>Exceptionally so. The gas valves are of that sort of cost alone -
>although this model might be very much cheaper.
>

I've been wondering if in some cases it's cost effective to buy new
boilers and just rip out the parts for spares
--
geoff