TRANE XL80 Propane Furnace not working
I have an older TRANE XL80 (1989) recently quit working. I discovered the ignitor was not glowing and traced it to a bad relay in the control module. I had the relay replaced, now the ignitor will come on and the unit fires up but will only burn for about 10 - 15 seconds then flames out. The ignitor stays lit, but it appears the unit is not getting propane. Propane Tank is full and Propane Hot Water Heater working okay.

If your unit has a flame sensor clean it.

See if there is 24 volts to the gas valve during operation and after shut down