My boiler has suddenly stopped receiving signals from the external switch. (models listed below).
I'm trying to isolate the faulty component. There is no fault code on the boiler. It seems to be simply waiting for a demand. Water heating is fine and not operated by the switch. I'm able to get emergency heat (by pressing +/- buttons together).
The external unit is a wired, wall-mounted time switch. It appears to be functioning, in so far as it has power and lights up when the switch is supposedly asking the boiler to fire. (CH ON)
I tried to eliminate a fault in the switch by manually jumping it. I removed it from the wall and connected the live to the "CH ON" terminal. No change. Did I do this correctly? The wiring looks like below. I connected
4 -> L (1 and 2 are not connected)
Further to the switch there are two motorised zone valves operated by remote thermostats. The remotes appear to be paired and working.
I tried to eliminate the valves by manually opening them. This works with the emergency heat boost, but doesn't affect the lack of signal from the switch.
I'm now contemplating whether to restore the control wiring to its factory state which the manual says was a link between two terminals on the PCB. Does this sound like a good idea?
What other things can I try to identify the fault?
- Boiler: Valliant EcoTEC plus 937
- Timer/Switch: Siemens RWB29
- Thermostats: Siemens RDH100RF with RCR100/433 receivers.
- Motorised values: Honeywell V4043H1056