Ah OK my apologies I missed that, so at least you know now that the thermostat isn't the problem...... Back to the drawing board then.
honeywell cm927 to valliant 937
- Thread starter Jag-1978
- Start date
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What you were saying is that by moving the wires over it should have kept the heating on constantly bypassing the thermostat.. Which it wasn't doing.. it was behaving the same way as before the wire change. still giving S.30 code. So wouldn't that indicate a stat receiver problem? not sure now
When the thermostat is 'on' terminals A and B will be electrically connected. And when it is 'off' they are not connected. All the thermostat is, is a simple on/off switch.
By joining the wires in A to B together, it by-passes the thermostat thus taking it out of the equation by making the electrical connection permanently 'on'
By joining the wires in A to B together, it by-passes the thermostat thus taking it out of the equation by making the electrical connection permanently 'on'
Which it wasn't doing so clearly something not right there....I wonder...
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Would a PCB fault not at least show as a F code. That is the thing that is bugging me most is that I have no error codes to work with.. I will have to get a boiler guy down.. just don't want someone to come over with a call out charge and not find anything wrong with the set up.. The fault is intermittent and it's sods law that it will probably be working during that moment in time...
If there was a say fan fault yes, however, on this instance no. Get someone who’s familiar with Vaillants. I work on the EcoTEC Pro range almost on a daily basis, so would know what to look for. Maybe if you post a rough location where you are, someone on here maybe able to help.
It could simply be a bad wiring connection somewhere, even though you've tried bypassing the thermostat itself, the wiring between it and the boiler is still in use, but I guess you've checked that already.
I've got a guy coming over tomorrow to have a look.. He will remove the honeywell since I'm considering changing it anyway to a Nest. He'll temporarily fix a manual wired stat as an interim and we'll check all the connection and see what happens from then onwards..
Thanks for your input its been valuable
Just to update the post.. got my boiler guy out and he stripped out the wireless Honeywell unit and replaced it with a standard wired thermostat.. Unfortunately same issues, the heating is behaving erratically again another night of no heat, in the morning it randomly kicked in and has been fine since.. kind of..
I asked him to completely remove any element of stat connection and just let the boiler run with the heating permanently on and this also gave the same result.. He's concluded that the PCB is iffy and we should consider swapping it out. Seems electrical not mechanical.. So that is my next port of call. I've got a local company who will test the PCB and do a swap out referb for me verses going for a brand new unit.. So think we will go down that road.
Jag
I asked him to completely remove any element of stat connection and just let the boiler run with the heating permanently on and this also gave the same result.. He's concluded that the PCB is iffy and we should consider swapping it out. Seems electrical not mechanical.. So that is my next port of call. I've got a local company who will test the PCB and do a swap out referb for me verses going for a brand new unit.. So think we will go down that road.
Jag
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