Worcester 240 Combi

[Toey]

Hello folks. I'm having problems with my worcester 240 combi boiler.

The pilot light keeps going out. Originally the system would run as normal but the pressure gauge would, eventually, read in excess of 3 bar then trip out (as expected). I checked the expansion tank (big red cylinder) and that was out of gas. Recharged it to 1 bar and tried again. Now, when the system is pressurised to 1.5 bar it stays there (maybe up to 2 bar) but the pilot light still goes out after a period of time (about 5-15 mins).

Also the burner will be working then will switch to only pilot light then the relay on the PCB hunts (if thats the correct terminology) for about 2-3 seconds after which the burners fire again. The clicking is very annoying and I'm not sure if its related to the original fault but I've included it just in case.

I have checked the thermocouple voltage going to the gas valve (without removing it of course) and it was reading 13mV with the pilot light on. The return to the gas valve was 8mV so having read some of the previous threads I am assuming thats its not brilliant but ok.

The the PCB and the microswitches at the diverter are clean and dry. The diaphragm was replaced about 18 months ago.

The hot water works as it should (except when the pilot light is extinguished!)

Has anybody got advice for things for me to check before I call out the engineer - I want to have as much possible information so I don't get flannelled or ripped off!

Thanks in advance

Toey[/u]

 

[Aquaheat]

I have come across this problem on the worcesters quite a few times and after checking all other safety devices eg: APS, rectification electrode etc the only way to cure the relay fault is to replace the PCB. It is quite a common problem and is just down to age. You will probably find that this cures all symptoms of your faults but it is fruitless trying to check for anything else until this is completed.

 

[Toey]

Thanks Jonjb I'll try that next...

 

[Kristoflampie]

I agrre , the PCBs on most older Worcesters suffer from dry joints which chuck up wierd and wonderful symptoms ie boiler working when you press the pcb down with a screwdriver but stopping when you let go , the pump plugs and mains connections are favourites........ only way to sort is replace the pcb