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.

In following up to prior answer: I do not appear to have 24 volts to gas valve. I see one lead comes from Control Module and the other from the low voltage transformer. Is there further troubleshooting I can do?

The control board is what gives the gas valve its voltage after going through all limits and pressure switch. If the hot surface ignitor is glowing it tells me all safeties are closed but if you don't have 24v on the gas valve at any time, I would say it's a bad control board(ignition module same thing).

You say the gas valve did open for 10-15 seconds? I would guess a dirty flame sensor. Bad ground wire somewhere.