Suburban heater question

[gwilkrrs]

Replaced furnace with a new one after blow out damage-
Connected wires (wire for wire) except 2 blue wires to thermostat- had to guess on what blue went to white and what blue went to red but 50/50 and can switch those 2

Clicked on thermostat and nothing- no fan spinning and never lit-

I tried a couple times figuring air in lp line but nothing-

Fuse is good and red light comes on when thermostat switched on-

Thoughts?

[chuckster57]

What are the 4 colors coming from furnace and what are the 4 colors coming from trailer?

[gwilkrrs]

I will look in am- I just cut the bundle at the connections so I could make sure they were re wired same way
1 for 1 if you will

[gwilkrrs]

This is the wire bundle I cut and used as a template

The 2 blues are in question but they aren’t the fan I think they are the thermostat as they are the 2 small wire mates

[ChuckS]

From the furnace control module wiring is

Red … plus 12 volts
Yellow… ground
Blue … both are signal wires and it does make a difference which blue wire is wired to what coming from thermostat or A/C control module board

One blue wire is plus and one blue wire is minus for signal wires to control furnace circuit board

[chuckster57]

The blue that has 12V positive is going to the thermostat and the other is coming from the thermostat.

When you turn the thermostat to furnace, the sequence starts once you ask for a higher temp.

Fan kicks on, purge cycle, lights and heats, reaches temp and goes into cool down mode. The blue wire with the positive goes into the thermostat and when you adjust the temp up, the circuit is “complete” and 12V is sent back to the control board on the furnace for the sequence. Once set temp is reached, the 12V signal is interrupted and the cool down begins.

Hope this helps.

[gwilkrrs]

I will double check the wiring

I tried it and the light in the breaker panel came on when t stat turned to heat but no fan I heard nor gas igniting
I switched blue wires around and same result

[chuckster57]

Originally Posted by gwilkrrs

I will double check the wiring

I tried it and the light in the breaker panel came on when t stat turned to heat but no fan I heard nor gas igniting
I switched blue wires around and same result

Which light? If it was next to the fuse for the furnace, you burnt that fuse.

[gwilkrrs]

Oh know my ignorance just reared it’s head on that one then.
Guess I will check the fuse and try again-
Wonder if the blow out damage blew the fuse and I never noticed

[gwilkrrs]

so i replaced the fuse-

now during the start up (per directions since i have never had unit running before) fan runs for a couple seconds (not 5min like directions say) and turns off so the "purge" cycle never completes.
the igniter never ignites. the book says it comes with a propane switch but doesnt say where.......

i switched the blue wires and had same results with fan running for a bit but not long....

last day of trip and it was 56 this am and the wife was not amused......

[ChuckS]

If the fan runs for a few seconds and then shuts off either your sail switch isn’t closing when the blower motor a8r closes it or you have a control board issue on the furnace

I would first check sail switch with multimeter and see if it has continuity across its terminals when you move the switch paddle arm..

This circuit must complete when blower starts up or there will be NO ignitor firing and no propane valve opening up

[chuckster57]

Originally Posted by ChuckS

If the fan runs for a few seconds and then shuts off either your sail switch isn’t closing when the blower motor a8r closes it or you have a control board issue on the furnace

I would first check sail switch with multimeter and see if it has continuity across its terminals when you move the switch paddle arm..

This circuit must complete when blower starts up or there will be NO ignitor firing and no propane valve opening up

That’s where I would start too. Did the furnace suffer any damage in the blowout?

[gwilkrrs]

So this is a replacement furnace since the original blow out when we bought unit destroyed the furnace. This was a takeout- installed but not used unit-

I pulled the unit to check it since my rig doesn’t have an exterior access-

Complete bozo move- complete ignorance on my part-

There is a damn on/off rocker switch hidden by the board on the unit I can’t access when installed-

Turned it on and blower started then unit kicked right on-

Man I feel so low but happy at the same time-

I got home and told the wife and she just smiled and said at least it was an easy free fix-

[chuckster57]

Originally Posted by gwilkrrs

So this is a replacement furnace since the original blow out when we bought unit destroyed the furnace. This was a takeout- installed but not used unit-

I pulled the unit to check it since my rig doesn’t have an exterior access-

Complete bozo move- complete ignorance on my part-

There is a damn on/off rocker switch hidden by the board on the unit I can’t access when installed-

Turned it on and blower started then unit kicked right on-

Man I feel so low but happy at the same time-

I got home and told the wife and she just smiled and said at least it was an easy free fix-

It happens, at least it’s working. I fixed a furnace in a big fifth wheel, tested it and it can up to set temp 3 times. Customer takes it home and it doesn’t work. Brings it back in and that on/off switch was off. No idea how it got flipped to off, so don’t beat yourself up, it can happen to anybody.