it had been on a twice daily hot water cycle during hte summer, when the wife complained the water wasn't very hot!

The boiler starts up, pump runs etc, but whilst the pilot light ignites the main gas burner fails to start.


a meter shows 240 volts across both the pilot and main valve coils. the pilot solenoid has a resistance of 12k, but the main valve solenoid, the smaller of the two appears to be open circuit.

Am i right in assuming that the main gas burner is not lighting because the coil has failed. if So any idea regarding the part number

gripsky, September 2008

I've never been to wales

Mr Never Been To Wales, April 2010

Main circuit board now replaced and all seems to be well (it has worked consistently for the last 48 hours). According to the engineer, this is the most common fault with these boilers. Mine's a 100e but I'm guessing it's just a bigger version of the 50e. He's going to come back later and re-install my old gas valve (White Rodgers) to save me £150.

It's so nice to be warm again!

Paul F., November 2008

I have a similar problem currently and have called in a local acclaimed boiler expert (not BG). It has been lighting the pilot and then the main burner for a while but then falls back to just pilot before getting the system upto tempertaure.

Yesterday the chap came and was initially going to replace the circuit board but when he did some electrical tests he decided it was the gas valve that needed replacing. It worked great for the rest of the day after this BUT then in the evening it was back to square one. No heat again this morning. It did the same thing after my regular plumber came to look at it initially. It seems that removing the case resets it temporarily. Could this be anything to do with the positive pressure and the associated circuitry?

I'll post the outcome on here cos' these pages are very useful to anyone with similar problems.

cheers,
Paul.

Paul F., November 2008

Hi Mick

My book shows 2 types of gas valves were fitted to this boiler but as you say one coil is smaller than the other it will be the white rodgers valve.

I dont know the numbers of the individual coils, I did buy one a couple of years ago but ny parts supplier said they were getting rare and it was his last one. The manual shows these part numbers for the gas valves.

Gas Control Valve — Honeywell ) 907704 or 395796

Gas Control Valve — White Rodgers) 907702 or 382988

Ian, September 2008

from the part number it looks like a White Rogers 36E16S-501 gas valve!!!

gripsky, September 2008

Thanks Ian,
there doesn't appear to be a spark once the pilot is alight. There is 240 volts across the common - main burner cable pair, so the would think the board is requesting a main burn. I checked and there is no current, as I say the coil reads open cct.

any idea of the part number?

I've found two
929097 or 45900406-003
but not sure which is the pilot coil, and which the main


regards
Mick

gripsky, September 2008

If you have 240v across both coils it would appear that the coil for the main valve is u/s, at one time you could just buy the coil.

If the ignition keeps sparking after the pilot is lit this is usually because the pilot is too small or the circuit board is faulty, this would also stop the main burner lighting

Ian, September 2008