Vaillant VCW242 ch goes off after few minutes won’t reignite

30 Dec 2020
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United Kingdom
We have an old VCW242 boiler that has had a leaking dhw heat exchanger

I’ve just replaced the leaking dhw heat exchanger and diverted valve, cut wire W18 as per instructions (hybrid model with plastic thermostat dial)

Diverter valve moves to left when ch is on, moves to right when hw is on and returns back to left when tap turned off.

Hot water is all good. Central heating comes on for a few minutes, rads get hot. Boiler then switches off and won’t reignite, rads gradually get cold.

Any ideas?
Last edited:
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Pump has 3 settings it can be switched to on a link try it in the position that makes it run constant it is probably in the one that switches it with the boiler stat , this may move any air out of the system
Thanks for the reply - fingers crossed it started working - must have been an air lock

Useful to know about pump settings

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