Got a strange issue where the boiler is stuck in state of s.30 which is no demand. Initially tested by looping pin 3 and 4 together and boiler fires up no problem for water and heating.
Assumed this was a fault with the thermostat so replaced with a new one. However boiler still not responding to any demand calls from thermostat. Thinking it could be the boiler PCB at fault but then it wouldn't have fired up when looping pins 3 and 4.
Only thing I can think is the Cables damaged somehow and just needs testing for continuity. Any other ideas?
Just to note no changes have occurred to the system before the issue and no fault codes have come up. Vaillant ecotech plus 612, 10 years old.
Assumed this was a fault with the thermostat so replaced with a new one. However boiler still not responding to any demand calls from thermostat. Thinking it could be the boiler PCB at fault but then it wouldn't have fired up when looping pins 3 and 4.
Only thing I can think is the Cables damaged somehow and just needs testing for continuity. Any other ideas?
Just to note no changes have occurred to the system before the issue and no fault codes have come up. Vaillant ecotech plus 612, 10 years old.