Arrrrggghhh... Baxi 105he, no central heating:(

[dar2008]

I thought it would be a good idea to replace my old Honeywell dial thermostat with a Honeywell cm107 programmer/thermostat combined The wiring is the same according to both thermostat's wiring diagrams with two wires connecting to two terminals in the combi boiler. Should be a straight swap (no?).

So I swapped them, programmed the new programmer/thermostat, turned the boiler electrics back on, but regardless of how high I put the target temperature on the CM907, the central heating doesn't fire up. Hot water on demand is working fine.

After searching the internet and scratching my head for a while, I decided to put the old dial thermostat back for tonight and look afresh at why the new CM907 isn't working tomorrow. Alas, even with the old dial thermostat back in position (with the same connections as before), the central heating still doesn't fire up

There are no errors indicated by the lights on the Baxi 105, but when the boiler first fires up, the central heating light flickers for a second or two before disappearing - it doesn't really flash.

Many thanks in advance for any ideas...

 

[kevplumb]

bugger youve broke it

link the stat out will get you heat for now

then double check the wiring

 

[dar2008]

I left the boiler with it's timer in the off mode overnight. This morning I moved the timer to 'on', and the radiators are suddenly working fine again, albeit still with the old thermostat. Absolutely crazy, I haven't done anything else other than give the old boiler a rest

I'll start a new thread about swapping my dial thermostat for the new CM907...