Potterton boiler Problem

[bav]

Can anybody help?
I have a Potterton Combi 80 boiler, which is about 8 years old. Last week I had a problem with system. The Rads were only getting warm (not hot). The water was working fine, although every now and again I would need to press the lockout button as the boiler would cut out. I cleaned the diverter valve and reinstalled it and the Rads started to get hot again and the water was fine. This lasted about 3 days and then the Rads, once again, started to only get warm or not come on at all. The water also has stopped coming out hot. When I turn on the central heating the boiler fires up for about 10 seconds and then flames go out although boiler pump continues to run. Same happens with the hot water, I turn on the tap and the boiler fires up for a few seconds (not long enough to give hot water) and then the flames go out (boiler continues to run).

When I open the diverter Valve the inside was all black, which I tried wiping clean (best I could). I have been told by somebody that the system must have a powerflush. Is this true or would you expect to find some black inside the diverter valver of a 8 year old boiler ?

I drained the whole system and water came out slightly brown at first.

Does this sound like a diverter valve problem or could it be something else ?

 

[ChrisR]

You probably know by now which way the water is supposed to go, when, so gripping the appropriate pipes inside and outside the boiler will tell you if the wrong ones are warming up, which will in turn tell you about whether the diverter is diverting or not.
The wax capsule could well need changing. Often leaks , easier to change the whole DV.

You'd expect black surfaces, but unless you have sensor(s) telling the boiler to switch off early, blocked up heat exchangers do sound likely.

 

[bav]

Thanks for your reply Chris. What used to happen was the pipe going connected to the back of the diverter valve was getting very hot and the pipe leading to the first radiator. But as soon as the pipe got hot the boiler flames would stop. After a while the flames would come back on for a few seconds and again go out. After a while (Few hours) the boiler would start working and the rads would go very hot and stay working. The boiler now just doesn't fire up for more that 10 seconds at any time and the pipe to the firs Ran and the pipe going into the back of the Diverter Valve is only slightly warm.