Potterton Lynx 2 - Overheating

[Alphas]

My Potterton Lynx 2 combi boiler is overheating. Basically, the CH will run fine for an hour or so but then after a while the boiler finds it difficult to switch its self off. If it does go off it seems to come straight back on again after a few seconds, then the radiators get unbelievably hot as does the boiler, then the CH overheat stat kicks in and kills the gas and it ends up going to lockout.

What does this sound like? I’ve already changed the pump and more recently the CH thermostat but it doesn’t appear to have made any difference. Does it sound like the main electrical board?

Also I’ve noticed that when the boiler is running, sometimes the gas valve ‘over modulates’ i.e. the flame goes high then low then high every few seconds. It’s also kettling when it’s doing this.

Thanks in advance for any help..

 

[Agile]

If its not an NTC then I would suggest it might be better to call a competent CORGi engineer who is familiar with your model.

It sounds potentially dangerous!

Tony

 

[Alphas]

Just thought I’d let people know I've sorted the problem (incase anyone else with the same issues reads this post). It was the PCB at fault.

After constant overheating and concerns that the boiler was eventually going to blow itself up one of my plumber mates suggested taking the PCB out and having look for any blown resistors/dry solder joints etc.. so I did, and sure enough a whole row of pins had completely come away from the PCB and were literally loose! I got the solder iron out and made right all suspect looking solders.

The difference is unbelievable, the boiler runs so much quieter and better than it did before it is like its brand new! Now finally the temperature controls on the front actually do something!!

I am considering getting a new PCB if the problems re-arise but at the moment everything is good so will leave it how it is!