I have an old Vaillant Sine18 T3 which was working fine until last week when for no apparent reason the boiler failed, no hot water or central heating but the pilot was on. Having trawled through these forums I discovered that the overheat reset had tripped (thanks to weargas reply to Beavis similar problem on this forum). Once the little button on RH the side of the PCB housing box had been reset the boiler fired up and both DHW and CH worked ok.
I was able to run a bath ok but when I turned the central heating on later in the day the boiler failed again and I once again had to reset the overheat switch.
I have now noticed that with either the central heating on or running hot water that the temperature gauge on the boiler above the pressure gauge never moves (remains on lowest mark) and I now suspect this may be related to the overheating problem.
Any suggestions would be much appreciated.
I was able to run a bath ok but when I turned the central heating on later in the day the boiler failed again and I once again had to reset the overheat switch.
I have now noticed that with either the central heating on or running hot water that the temperature gauge on the boiler above the pressure gauge never moves (remains on lowest mark) and I now suspect this may be related to the overheating problem.
Any suggestions would be much appreciated.