[jsb5717]

If the furnace is igniting or attempting to ignite then it's a post-ignition issue - propane regulator, propane controller in the furnace, igniter distance from burner, bad temp sensor, main board. If not igniting or attempting to ignite then a pre-ignition issue - sail switch, bad igniter, main board

A lot of potential issues depending on the symptoms. Set the thermostat to

Set the thermostat to Furnace, turn up the temp, and listen carefully to all that takes place. Report back here for more help.

Ours was a faulty propane regulator. The furnace demands a higher PSI than the other propane appliances so while the other items will continue to work normally, the furnace may fail if the regulator isn't performing at full PSI.