When the hot water tap is turned on, The water heats up and cools down cyclically. Looking at the boiler, the boiler turns on and off (about 1 minute cycles). Any thoughts? Is it the thermostat?

Kevin Hayes, December 2007

Kevin,

I had same problem 3 -4 years ago, changed the thermister but also found that the relay at the front of the board had come unsoldered due to the transformer heating it up. This relay needs to be on to kick the fan in which in turns triggers the air switch thus allowing the ignition. This also has some effect on the heating but as the cycling is every minute or so you don't realise.

Problem I have at moment is that all the bits to do with the air switch are 10 years old and become brittle - if you are testing the switch be careful not to break the hosetails on the fan as I have - no plumbers shops open Boxing day so blankets all round.

Hope this helps too

Cheers

Martin

Martin, December 2007

kevin, i had the same problem last year and it was cured by changing the thermister on the hot water supply (not heating supply). The problem has just arisen and i am hoping that doing this again will cure it, though i thought the new part (cost approx £8.00) should last longer.The plumbers mechants do recommend changing both but as there wasnt a problem on the heating i never bothered.
hope this helps...... joe.

joe, December 2007