Red light on wont reset .changed the thermistor and it worked for a few days. now gone back to the red light on and wont reset. Is this likely to be the pcb ?
To know for sure if the pcb is fried you would have to do a series of tests on the existing pcb
Checking voltages resistances etc
If you feel confident about checking electronic components
and have a decent multimeter
and consider yourself a competent person
And are able to follow the fault finding guide in the boiler book
Then it should be relatively easy to determine if the pcb needs replacing
However
New pcbs for this boiler are very expensive
You need to be 200% certain that you have followed the correct procedure for determining a faulty component
Otherwise this will be a very expensive learning curve for you
Try ringing baxi/potterton tech helpline for a step by step guide thru the test procedure
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.