I have switched off the central heating for the summer but the radiators still get warm when the hot water is on,.
This is the first time its happened
What causes it?
Faulty diverter valve, the motors burn out after a time, if its easily accessible you can manually move the lever across & lock it in place if this stops the fault then chances are it the motor, a couple of quid from most places & are easy to replace.
From the description of your fault then I think you may have a Y plan system with a 3 port valve. so the motor in the valve is not energised on hot water.If it works on heating then the motor is ok and you can easily test that yourself.Its more likely to be the valve itself not closing of the ch port 100%,either caused by system debris on the valve seat or the spindle is siezed.If you have 2 zone valves fitted then the fault is as above and not a burnt out motor
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