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Just for information BAXI 105E

whjohnson

Been fault finding on my old combi and having solved the problem I would like to share the solution with those who are still running the old Baxi Water Hotter!

Model of boiler is BAXI 105E combi - Not a condensing combi. This model is around 20 years old.

Nature of fault - No hot water, fan failure fault light on, and flame failure fault light on.

I initially changed the complete diverter valve assembly because the original one was leaking and badly corroded, although this was not actually causing the fault.

I traced the fault to a relay on the pcb which actuates the fan. For information, the relay is marked RL.1

This applies to a Honeywell pcb with the following markings printed on it -

CE 00518L 1810

CS0118E-LS

TYPE:MIDINT00

CD 995099 2

CD 565599 2 

I sourced a replacement relay from ebay, in fact I bought 2, since there are 2 identical relays on the pcb so I got a spare.

Relay part no details - 

TAKAMISAWA JV24S-KT

5A 30VDC

250VAC

SPST

Coil voltage is 30VDC, cantact voltage rating is 250VAC

I unsoldered the original relay and connected 30VDC across the coil and a multi-meter set to ohms across the contacts - result was open circuit.

I repeated the process with the new relay and got continuity across the contacts and a satisfactory click as the coil energised.

I had a spare pcb but that didn't work at all when I just did a straight swap. Anyway I hope someone finds this info useful.

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    I think many Gas Safe ‘Engineers’ are of the simple photocopier service engineer mentality - monkey engineering - if that pcb doesn't work, swap it, then if that doesn't solve the problem, then swap the next and the next and the next until it does work. There are some good plumbers out there and there are some good design engineers out there but it is rare for a plumber to be both.

    Being a nosey git, I would love to learn how the gas valve is modulated. I assume there is a sensor and a chip involved. It isn't like our old industrial gas furnace control - a few thermocouples and a full-on or full-off gas solenoid on each of the12 burners.

    The older your boiler gets, the cheaper the spares become - I wouldn't have paid £100 for a pcb for an old boiler though.

    Hope it works out for you.

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  • 0

    I think many Gas Safe ‘Engineers’ are of the simple photocopier service engineer mentality - monkey engineering - if that pcb doesn't work, swap it, then if that doesn't solve the problem, then swap the next and the next and the next until it does work. There are some good plumbers out there and there are some good design engineers out there but it is rare for a plumber to be both.

    Being a nosey git, I would love to learn how the gas valve is modulated. I assume there is a sensor and a chip involved. It isn't like our old industrial gas furnace control - a few thermocouples and a full-on or full-off gas solenoid on each of the12 burners.

    The older your boiler gets, the cheaper the spares become - I wouldn't have paid £100 for a pcb for an old boiler though.

    Hope it works out for you.

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