Furnace blowing warm then cold air
I have a 98' Jayco tent trailer, our first trip out this spring the heater blew warm air for about five mins or so then cold air the rest of the night. That same weekend we blew the gfci and lost all electricity. We replaced the gfci but we still don't have heat.
We fond the circuit breaker and everything looks good.
Its like its not getting enough heat, you can hear the propane click on at first it lasts anywhere from 3-10 mins, then it blows cold air. If you leave it alone it will continually blow cold air. If you move the thermostat back down to cold then up to heat again. The whole process starts over or it just blows cold air. I should also note, the hot water works well as does the propane stove.
This year the heater has never gotten the whole trailer up to the setting on the thermostat.
Do we need a new furnace? Is that something we can do ourselves? Right now we're using two ceramic heaters which work really well when were hooked up, but we were dry camping last weekend and it was really cold!
Thanks in advance!