"crb" wrote in message
...

IME the best way to trace these sort of very intermittent electric/
electronic faults is by using a data logger; they can be bought on
ebay for around £70. A data logger can be useful for other
applications too, for instance I traced an intermittent engine cutting
out fault on my daughter's Focus that a main Ford dealer had been
unable to find. I have also used it for for fine-tuning central
heating etc.
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How did you fine tune a CH system with it?