Old Baxi WM 531 RS boiler problem

interesting

The smell could be coming from the mercury substitute inside the coupling which would mean it is split and the leaking liquid. If it has corroded inside the tube, then it will need carefully drilled out to remove any residue of the old casing.

interesting

Sounds like you have the type of thermostat which has a bulb containing a volatile liquid (ether or some such) connected to a pressure sensing switch by means of a capillary tube. The whole thing is a sealed unit and no longer works if it develops a leak. You'll need to remove and replace the whole thermostat assembly.

It the stat doesn't work, it won't switch off the boiler when it gets up to temperature - so it will overheat, causing the banging noises which you witnessed.

DO NOT RUN THE BOILER without a working stat!

Roger

Oh shi*t! What has happen is that the thermostat has failed big time. The consequence is that the boiler has now boiled. The thermostat consists of a phial, capilliary tube, gubbins and a user knob. The liquid in the phial & tube was probably alcohol, hence the smell.

Essentially the repair job is simple as the new unit consists of new gubbins attached to a tube and a phial and a few electrical connections to the gubbins.

You can get the manual from the manuafacturer. You might even be able to find it online.

The part is likely to cost less than 25 quid (maybe much less). Given that you are not familiar with boilers you should probably get some help. Although with the manual you would probably do just fine.

This boiler is up for renewal but the thermostat would still be worth replacing to get you through to the civilised part of the year for boiler replacements.

Okay - thermostat has been removed and the bulb part has been drilled out. I did this very carefully and everyting took me the best part of 2.5 hours. I am SOOOOOOOOO glad I did that part myself! Okay a proper engineer may have done it quicker - possibly taking less care - but I'm glad I've done it now.

Next problem - sourcing a new thermostat.

The thermostat has the following markings on the bottom:

RANCO

I guess its a 16A thermostat which turns off at 107 degrees C.

On one side of it it's got 102027 and the other side has G1 11685 49 75 1P.

Baxi 102027 Thermostat K36P1324 Thermostat K36P1324 .(Please note Baxi re-numbered this part several years ago. If the part fitted is marked K36P1324 order this part. If the part fitted is marked CL6PO115 use 235464)

Price: £12.20 (Excluding: VAT at 17.5%)

So - if I need to ask around for the thermostat - do I ask for 102027 or K36P1324?

Any other good sources of this part?

The other thing I wondered about was whether I could get the probe/sensor separately. Its a sealed tube and I've removed it all, and it would be easy to keep the 'gubbins' and just replace the tube. The same page lists:

Baxi 230204 Thermostat Sensor Thermostat Sensor (379-030)

Price: £9.13 (Excluding: VAT at 17.5%)

Judging by the price difference (and the fact I've no idea if that sensor is the same thing as I've no part number for that bit) - I think its probably best to just replace it all.

Thanks for your help - you've saved me a bunch!

Hmm, searching around further, there seems to be a couple of thermostats labeled 102027. For example,

So - does anyone know which thermostat I'll need for a Baxi WM 532 RS CHB boiler who's thermostat is labled 102027?

Thanks

David

probe/sensor

You might have to resort to ringing Baxi's technical support line on (National Rate) 08706 096096.

Roger

Thanks for that. I gave them a call and was told that as I wasn't Corgi registered I couldn't speak to the technical support team, and after saying what I was calling about got put through to a Spares number. They confirmed there were two parts, and that either were suitable but suggested one.

I called KeepTheHeatOn.Com who also were very helpful and pointed me towards the same one which Baxi Spares pointed me. They admitted they'd made a mistake on the price on their website (it had been on offer last month and not restored to original price and honoured the cheaper price!) and quoted me £9.20 + VAT and £4.50 (guaranteed next day delivery) and had 23 in stock. My local place quoted me £23 (I guess + VAT) to get it into their place sometime tomorrow. I went with KeepTheHeatOn.Com (and gave my local place the URL as they'd not heard of it before and said they couldn't beat that price!).

I'm glad I sorted it now. Okay, its cost us £16, 2.5 hours of my time, and (worst part) 48 hours without central heating. But I think its signfificantly cheaper than the cost I'd have had to get a plumber to drill it out and replace it (which would have needed to have been done when/if anyone needed to open up boiler).

Thanks for all your help!

So - you have read the FAQ below? You have found the plate with the GC number on it on the boiler.