Hi Mac,
If you have more than 1 thermostat, you might be operating the wrong one. Only one thermostat operates the furnace.
If you're on the right one, when you switch it to HEAT and the thermostat set point is higher than the ambient temperature, here's the normal sequence:
- A relay, usually overhead, will click to send 12V DC to the furnace.
- The furnace blower will start, and will push cool air through the floor ducts for about 25 seconds.
- The gas valve on the furnace will open and there will be a spark applied to ignite flame.
If the furnace blower doesn't run, check your fuse box to see if the 12V DC fuse is blown.
If the blower runs for more than 25 seconds and then shuts off after 3 ignition attempts, check the propane supply. You might need to purge air from the propane line, which you can do by lighting the burner on the range and letting it burn for a minute.