For one unit of my heating system, the fan doesn't come on when set to AUTO. It works fine when set to ON. Replacing the thermostat didn't solve the problem. (At first the boiler was also not coming on but this was solved by replacing a relay.)
For my other two units, I had the same problem but worked around it by setting a switch on the existing thermostats to ELEC instead of GAS, even though my boiler is run with gas.
Does anyone know what the problem might be?
Thanks