Procombi 100he fault

[bewsh]

Aright guys?

looking at the above boiler for a friend. Boiler has a solid red fault light, MIs say thermistor fault, but all thermistors testing fine and boiler won't reset, even if turning power off. Fan also runs constantly with no demand. Checked all 3 ntc, overheat, aps, etc... And they're all testing fine. I'm thinking pcb fault, but just want to see if anyone has any ideas on it before I order a pcb.

also, it did reset eventually after I turned the power off for about 5-10min, and worked fine then.

any advise is greatly appreciated, thanks!

 

[quality]

Check the venturi is not blocked

 

[bewsh]

Don't think that would cause the fault, would it? But it's not blocked, the aps closes when the fan is running. Thanks though

 

[tamz]

If it is the vokera version of the procombi it needs the main pcb (not the ignition board).

The clue is the fan running constant.

Sell them a new Easy Heat and emphasise the 5 yr guarantee. Straight swap easy money.

 

[quality]

Ive had a couple round my way (2) where the fan spins constant with no demand with blocked venturis

 

[tamz]

If the fan is running constant with no demand it is the pcb. The fan running is holding the pressure switch open so the boiler won't or cant attempt to light.
Pull the hose of the pressure switch, set a demand then stick the hose back on. It will fire and run until it gets up to temp then won't light again.

 

[bewsh]

Cheers for the help guys. I was 99% sure it was a pcb fault, just wanted to check that there wasn't anything I was missing!