'Fan on' not working in basement true air system

[reilersjr]

Hey all,

First post but have been searching for 2 days now and haven't found any resolution to the current 'issue.'

2001 Winnebago Journey 36L with Coleman Mach True Air in the basement:
1. Works fine in Electric heat mode(inside fan comes on and both compressors run. If temp difference is greater than 4 degrees, furnace kicks in. This is expected behavior.
2. Works fine in Gas heat mode.
3. Works fine in Cooling mode. Both compressors kick on, inside and outside fans run. In fact, there is a 1 amp difference in Hi/Lo fan setting. So I am assuming that is working as well.

What does not work?

1. Set mode to 'off', change fan from 'Auto' to 'On'. No fan, nothing happens.

I have tested at the control board with a volt meter pins 9/4(low indoor fan and ground) and pins 7/4(hi indoor fan and ground). Both produce ~13 VDC when stat set to appropriate mode, however, fan only still does not run.

I bought the rig used and it looks like the control board is new as it's a 6535A320.

Anyone ever seen this before? Any more ideas on how I can test.

Thanks,
Rick

["007"]

Welcome to irv2.
Here is a PDF with flow charts that may help you.
Most problems I have notice turned out to be a new thermostat needed.

[DancinCampers]

In the cooling mode, with temp set above room temp, does fan only work? If not I suspect switch contact, a little spraying with contact cleaner might help.

[reilersjr]

"I have tested at the control board with a volt meter pins 9/4(low indoor fan and ground) and pins 7/4(hi indoor fan and ground). Both produce ~13 VDC when stat set to appropriate mode, however, fan only still does not run."

Sorry for the confusion, this statement is a bit misleading. When the Mode is set to 'off' and the fan mode is set to 'on', I get 13 VDC at pin 9 when speed is set to 'low' and pin 7 when speed is set to 'hi'; however, the fan does not turn on.

See, this leads me to believe the thermostat is ok. I know that when in heat mode with fan set to 'on' when temp rises to set point, everything shuts off. Fan does not continue to circulate air.

I even jumped pins 9 and 2(low fan and +12VDC) to test just the fan and the compressor kicked on! Then when I let go of the jumper, the furnace fan ran for about 30 seconds then stopped.

I'm leaning more towards a bad control board still. Any other ideas on determining the issue?

Thanks!

[DancinCampers]

If everything works in heat/cooling mode, then I still suspect tstat. Pin 7 and 9 are used both in the auto cooling mode and manual fan mode, activating the same set of relays on pc board. The mode switch and fan switch are the only added items when in manual mode.

The test I indicated would eliminate an issue with the auto/on switch, leaving me to suspect the mode switch.

Tstat schematic shows the mode switch, in off position, feeding 12v to the fan auto/on switch.

In heat-pump mode, all compressor/fan operations are done by the pcboard, vice tstat. The only thing the tstat does is make or break voltage to pin 8 and send control voltage to lp furnace.

In the cooling mode, the hi speed indoor fan control voltage goes thru the EMS, but since it is working in the cooling mode I don't suspect a problem there.

[reilersjr]

I see now what you're saying. :-) Will test it out and go from there. I really, really thank you for the help. Will post back with results shortly.

Thanks again,
Rick

[reilersjr]

Quote:

Originally Posted by DancinCampers In the cooling mode, with temp set above room temp, does fan only work? If not I suspect switch contact, a little spraying with contact cleaner might help.

No, sadly it did not work. The contacts are clean as I've now cleaned them twice with electrical contact cleaner.

I think where I'm still a bit baffled is: applying +12VDC to pin 7 or 9 causes the fan AND compressor to fire up. I thought that should only run the fan. Am I misreading the schematics?

Thanks again for any help,
Rick

[reilersjr]

The solution: I ordered a new control board from the awesome folks at RVP direct. When it arrived, I installed it as per the instructions. First test, heat mode... Worked as expected. Second test, cool mode... Worked as expected. Last test, Fan Only mode..... Turned the switch, watched the amps jump up and then level off... No air blowing out of the vents inside, but it sure sounds like the compressor is trying to start. I flip the switch back as I don't want to burn up the compressor. I ponder for a couple of minutes and go through the same motions yet again. Same result. Now I get my helper to go inside and operate the fan switch while I'm outside at the unit so I can hear exactly what is going on. She flips the switch and... The OUTSIDE FANS start running!

Turns out that the previous installer had switched the inside blower for the outside blower.

The new board was the trick as all it's circuitry worked. I would have never figured out they were reversed without the new board as the old board did nothing switching to fan only mode. Maybe thats why they reversed them in the first place.

Again, thx a ton for everyone's help!

Rick