Trane XL1200 gaspack problem

Nov 04, 2019 4 Replies
C

I have an older Trane XL1200 gas pack furnace/AC. I just tried to turn on the furnace and nothing happened. Looking at the control board the led code told me it was a pressure switch problem. The inducer fan was not turning (rusted stuck). I replaced the inducer fan and now the furnace will go through the start-up sequence (check high limit switch, check flame rollout switch, turn on inducer fan, check pressure switch, turn on spark igniter, send voltage to gas valve) but it fails to light and goes into system lockout (no flame). I checked the voltage to the gas valve and it was 60V AC while the igniter was firing! The gas valve would click but the furnace would not fire. It should be



24V AC. To check the gas valve I disconnected the wiring from the valve and I connected 24V AC to it and it would click but I could not hear gas flowing or smell any gas. Do you think the gas valve is bad or the control board since it is supplying 60V AC to the valve?
Vote
Twitter Facebook LinkedIn
T

If you apply 24v to the gas valve, it clicks and there is no gas flowing, I would verify there's gas at the furnace. Maybe debris in the valve? 60v at the valve, no idea what that's about. I would check supply voltage to board. Maybe a relay failure has 120v crossed into low voltage side, but you'd think there would be smoke, burned up board, etc

Vote
Twitter Facebook LinkedIn
D

I'm a bit surprised that 60 volts didn't fry the gas valve. That's about 2.5 times what it's supposed to get.

Vote
Twitter Facebook LinkedIn
T

24v he said. I wonder if this is a measuring problem, operator error? What happens if you have the meter set for DC instead of AC? I've done that, but don't remember the results. Hard to imagine there is 60V there, as the control board would just have a relay that it closes to apply 24V from the transformer to the valve. I suppose the transformer could have a short, be bad, but seems that should have cooked the board, blown a fuse, etc.

But he said he applied 24V to the valve, it clicked, no gas. That would seem to indicate a problem with gas supply, debris in the valve, etc. I've seen furnaces have no gas due to the pipes corroding underground and filling with water. I'd work on checking for gas, then unhooking the gas pipe, energizing the valve and try blowing in the pipe to the valve and see if it passes air.

Other funny thing here is he said it started with the inducer motor being rusted and bad. Usually you only have one problem. Wonder how long this thing has been sitting unused?

Vote
Twitter Facebook LinkedIn
D

Maybe it's one of those really silly things one assumes is right. Is the gas on at the meter type of problems. I wonder if he has other gas appliances in the house to use for reference.

Vote
Twitter Facebook LinkedIn

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required