My central heating system was working fine at the end of Spring. It was idle for approx 3 or 4 months. Having recently switched the central heating back on, I found that the upstairs radiators were heating up, but the downstairs rads remained cold.
As the system is quite old, I suspected...
I'm having the same problem with my CH pump in that it never stops running even when the programmer is switched off and the HW & CH thermostats are turned down to off.
When you refer to the PCB, I take it you mean Printed Circuit Board. Is this to be found inside the programmer? If this is...