When we are running hot water through our valiant combi boiler, the water cycles though hot and cold and never stabilises to a constant temperature. This has been happening for a few days.

On running thought the diagnostics on the boiler it would appear that the problem could be the main switch board, but I not am a plumber so I really have no idea.

Does my diagnosis sound feasiable? If so, Is this expensive to repair?

Paul Rostron, September 2007

100% its the dhw heat exchanger, remove it, pour neat fx2 in the connection holes, put in bucket, pour boiling hot water on top, leave 4 1 hr, refit

kris, September 2007

OK so on futher investigation i was wrong, my thoughts are now heading toward the DHW heat exchanger or the microswitch....... any confirmation would be gladly recieved

Paul Rostron, September 2007