A lesson learnt!?

Initially, pilot light not staying on.

Obvious remedy...new thermocouple, or so you would think!

I am a plumber but also 'dabble' with heating. I had a spare (brand new) thermocouple and so fitted it to my boiler, but the pilot would still not stay lit.

I then replaced the thermocouple re-router (connector lead) but still no go. Next was a new pilot burner, but to no avail.

It was then apparent that the gas-valve (magna- coil) was faulty, and so I replaced the gas-valve. Everything was now working perfectly...but after 6 weeks the flame failure device kept operating, shutting the burner and pilot down within minutes.

All connections were checked for tightness etc., including the thermocouple. The flue was checked and cleaned, as was the main burner, injector and heat exchanger. A new thermostat and pump were fitted, followed by a complete power flush of the system, but all of this still made no difference.

Total spend on parts = £408-00.

Decided to fit another thermocouple...you guessed it...perfect!!

Why are thermocouples such crap things and completely undependable?