Worcester combi 24 RSi overheat problem

[kevturner100]

I have a fault on a combi that is tripping the overheat on the top of boiler on occasions when heating's on and hot water is run, generally when taking a shower.

Checked the overheat stat and seems ok tho haven't replaced it. Does not trip if heating called for OR hot water demand called for individually.

The manual isnt much help.

Any ideas anyone? Corgi reg no 1705

 

[gavinda]

check the main heat exchanger on this, my old one had a similar issue which i lived with for a while (dont we all ) when i finally got round to looking at it, all the pressures and stat readings were fine, but half the fins on the hex were gone .