Greenstar 37cdi combi not communicating with thermostat?

[markjg123]

Greenstar 37cdi combi not coming on even though thermostat is calling for heat. It is operating normally for hot water. It's due to be serviced in a week but would like heating on now. Any suggestions for a self fix? I've attached photos showing the thermostat calling for heat and the green light is on the receiver. The heating light is not on the boiler though. The thermostat and receiver model is Altech ALTHC014.

 

[CBW]

Could be the diverter motor is stuck, try resetting the boiler.

 

[markjg123]

Sadly that's not made any difference.

 

[CBW]

Could be a malfunction of the room thermostat, is there a manual override? If not you could join the 2 signal wires together. Make sure it’s nothing as simple as batteries to the wireless thermostat.

 

[markjg123]

Batteries are brand new. I don't know if there is any manual override. How do you join the signal wires together?

 

[CBW]

Safely electrically isolate the system, remove the Altech receiver cover and join the ones that aren’t L and N, probably com and NO.