Trane XR80-Intermittent No Gas

[Jeepster04]

Gotta love those intermittent issues. Years ago it took me almost all winter to figure out an intermittent shut off issue. Sometimes it would light, kick off, light, never kick back on, etc. Turned out it was a cracked solder joint on the board.

9 years later I come home last night and the blower fan is running. Idk why, but trane made this thing run the blower indefinitely if it has an error... Seems like a great idea...

Anyway, gas valve wasnt opening. It tried 3 times and would throw an error.

Wake up this morning and wanted to check to see if the gas valve was getting 24v before I went to work so I would have an idea of what to order... It kicks on no problem... Been working fine all day...

Sigh... I've got a gas valve on order as its giving the first ~20F temps of the season. Figures it would wait till the first serious cold front to hiccup. Hopefully its not the PC board. I could hear the relay clicking so Im hoping its ok.

 

[fitter30]

Any flashing lites on ingniter board?

 

[Jeepster04]

Yeah, two flashes, which is 'exceeded attempts' or system lockout.

Watched the temp in my house while at work today and around 11 the temp started dropping, so I knew it wasnt kicking on.

Got home and this time I was able to get a volt meter on it, 2-3v to the gas valve.... So I wasted $45 on that.. O well.

Checked the transformer, 24v. Started tracing wires and just as it was trying to turn the gas valve on I touched the main plug on the PC board and the flames kicked on... Thats where the cracked solder joint was 9 years ago except it was the circuit for all of the safety devices.

I've ordered a new PC board, $100 on amazon. Hopefully I can limp it along till it gets here next week.

 

[Jeepster04]

Ended up being more cracked solder joints. May solder up the joints and keep it as a spare.

Something neat that I read. Im not sure if the original board did this but it often times took two tries to fire up. New igniter made no difference.

New board says that it will max out the volts to the igniter then the following ignition cycles it will lower the voltage to the igniter. Once it doesnt light, it will go back to the voltage that it was at 4 cycles previous and stick with that. The two ignition cycles its had thus far it lit first try...

 

[sms1974]

Ended up being more cracked solder joints. May solder up the joints and keep it as a spare.

Something neat that I read. Im not sure if the original board did this but it often times took two tries to fire up. New igniter made no difference.

New board says that it will max out the volts to the igniter then the following ignition cycles it will lower the voltage to the igniter. Once it doesnt light, it will go back to the voltage that it was at 4 cycles previous and stick with that. The two ignition cycles its had thus far it lit first try...

Common problem with those boards... The original board would have been the same as far the ignitor voltage that was original engineered to increase the life of the ignitror. Otherwise these are some of the best furnaces of that era.

 

[jonshonda]

I had to go and open this stupid f@cking thread yesterday and now guess what happened this morning? Wife wakes up and starts complaining about the house being cold. Go check the furnace (Trane XV90) and the red light is blinking twice. I turn the furnace off for 30 seconds then back on. Fires up just fine.

Heat runs until it hits the desired thermostat temp. I then turned the heat up again and go down to listen to the old girl sing. It wouldn t fire on the first try, but did on the second. Last year I had the orifices cleaned and cleaned the flame sensor due to other issues. What should I try this time?

 

[Jeepster04]

Common problem with those boards... The original board would have been the same as far the ignitor voltage that was original engineered to increase the life of the ignitror. Otherwise these are some of the best furnaces of that era.

Its possible that the ignition pin also had a cracked joint since it is dark brown. Maybe its been cracked for many years.

It was rather warm outside yesterday but the one time it fired it, it had a very satisfying sound as the gas lit. Before it sounded like a small explosion.

Johnson, being at the unit when its trying to light and doesnt light would be when you could determine whats going in. If the gas valve is turning on but it doesnt light then I would look at the ignition system. If the gas valve doesnt turn on then check for 24v to the gas valve. Hard to say ‘it could be this’ without doing some diagnostics.

 

[jonshonda]

It was dirty gas orifices. Had the same issue in March of 2018. WTF!

 

[MFolks]

Most if not all PC boards are wave soldered,may be tested, but may not be rung out/burned in, under a load.