Troubleshoot furnace

[rcosta]

I am having my first issue with my furnace. Just got it back from the repair shop (exterior issues) and plugged everything in and ran it. The blowers on the furnace are working but blowing cold air. My hot water heater is working, so I know the LP is ok. This is new to me so are there any good places to begin to troubleshoot? Thank you.

[brulaz]

rcosta wrote:
Thanks. I tried the burners and they are fine.

My furnace refused to light even though the propane hot water heater and range and frig all worked fine.

The problem was the regulator at the tanks. Provided enough pressure for the other appliances, but not enough for the furnace.

Have someone check the regulator and gas pressures.

[Old-Biscuit]

Plugged into shore power..converter supplies 12V DC system.
Furnace fan runs on DC power so you have DC.

Whether you have enough DC voltage is the question.
Furnace fan has to run at 75% or better of rated speed in order to make up 'sail switch' which allows DC power to circuit board for gas valve & ignitor operation.

What Brand/model of furnace
Suburban..NT, SF etc.
Atwood 7900, 8500 etc.

Brand and model makes it easier to describe what/where----unless you want generic answers. Kinda like "How long a piece of rope?"

[rcosta]

Thanks that might me it. I am on shore power but the battery is in bad shape. I will check tomorrow to see if it is better.

[midnightsadie]

yep need a 12v battery even when plugged into shore power.

[enblethen]

What type of work did the shop do? Anything around the furnace outlet?
Do you have the rig plugged in or is it running on battery power? Battery power, the battery could be low enough to not allow the fan to come up to speed so as to operate the sail switch.
Make and model of furnace?

[rcosta]

Thanks. I tried the burners and they are fine.

[JAYHAWKERS]

My guess would be you still have some air in the gas line going to your furnace. Try you burners on the stove and see if they light.