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Old 11-08-2021, 09:56 AM   #1
Join Date: Jul 2021
Posts: 34
Coleman mach HVAC big picture and component locations

On my 2003 Discovery 38u, I recently had a power surge that wiped out the thermostat. . . Temporarily. . . That is, I eventually found a procedure online to reset the thermostat, and it came back to life. But since I've always hated that tiny screen on the thermostat, and its funky operation, I also became enlightened about the new WiFi/Bluetooth thermostat made by MicroAir, and ordered one of those. It plugged right into the same connector, and worked perfectly right out of the box. In fact, now the fan speed on the AC units works like it is supposed to, and it never had worked properly before. So now I can make sure Fido is OK while we are on a walkabout, see and control everything from the cell phone.

But now that I learned a tiny bit about this Colman mach setup, I need to know more. You see, my zones have been wired wrong from day one, with the front furnace being on zone one, but the rear AC on zone one. Zone two just the opposite. I'd like to fix this, and I bet it is just a matter of swapping two connectors at the control boards. Holy crap, I looked everywhere, and I don't see where those control boards are hiding! I did find two tiny ckt boards on the wall of the power compartment, behind and above the inverter, but they are only about 1" X 2", and not in a box or anything. What the hec are those for?

Of course I have reviewed all the wiring diagrams, both Fleetwood and Freightliner, but mostly I just shake my head when examining those worthless diagrams. (Who trained those guys on documentation, and is it too late to shoot them?) So, anyone who knows where to find a big picture diagram of the 2 zone Coleman mach system, please send me a link. And, if anyone knows where to find the control boards for this Discovery Colman Mach system, please post a hint, and you will be my best friend all day long.
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Old 11-09-2021, 11:52 AM   #2
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Location: FT on the Road
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I'd contact MicroAir and ask to speak to someone. They are super knowledgeable about the whole setup including the wiring.
They were helpful to me. Sounds like your wiring is a bit messed up. No surprise there with the "quality" control at Fleetwood.
Only problem with my MicroAir TStat is it loses the wireless connection every so often so not a fail safe if you are away from your rig. The schedule works great. Love the features!
I don't make it much on here anymore so will not see your reply to my comment. Drop me a direct message and when I come back on I will see it.
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Old 11-27-2021, 09:38 PM   #3
Join Date: Jun 2010
Location: Toronto
Posts: 38
You can access the circuit board that controls both front and rear zones for a/c and heat by removing the ceiling trim for the rear unit or you can get to it from the roof. The latter preferable. There you will find all connections you are looking for.
I doubt the thermostat was the issue to start with.
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Old 11-28-2021, 11:04 AM   #4
Join Date: Jul 2021
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New Micro-air Thermostat is great!

Originally Posted by islandbob View Post
You can access the circuit board that controls both front and rear zones for a/c and heat by removing the ceiling trim for the rear unit or you can get to it from the roof. The latter preferable. There you will find all connections you are looking for.
I doubt the thermostat was the issue to start with.
Sorry for the delay... The new thermostat corrected the zones being reversed problem, so now both heat and cooling match the proper zone. It also works SOOO much better that the old one.

I'll check out the board from the roof side soon though when I get up on the roof, and try to learn more about this system. What I think you said is that this one board controls both AC units. But, does it also control the furnaces, or are they interfaced in a different way? (Still looking for a wiring diagram of this system that is readable by a human.)

One more issue: I'd like to make sure that the thermal sensors are working with the proper zones. I think that there is one inside the thermostat, and another on the wall next to the dinette. I assume the one inside the thermostat is hard wired to a particular zone. Which zone would that be?
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Old 11-29-2021, 08:42 AM   #5
Join Date: Jun 2010
Location: Toronto
Posts: 38
The senior in the Thermostat is for where it is located. The remote is for the other zone.
The ceiling board controls both a/c and both furnaces.
If I remember correctly there is a circuit diagram on the inside of the metal cover on the ceiling in the rear unit. If not there then inside the metal cover on the roof.
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Old 11-30-2021, 08:46 AM   #6
Join Date: Jul 2021
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yes, but...

the thermal sensor inside the thermostat is obviously supposed to control the area where the thermostat resides. but the question is, would that be called zone 1 or zone 2 or ??? in my case, the ac and furnace for the rear, where the thermostat is located are wired to zone 2. but the hard wiring could be reversed, tieing the controlled units to the wrong zones and thus the wrong sensors. in that case, when the sensor in the thermostat called f0r heat, heat would not be supplied to the rear area where the thermostat lives, but would instead be supplied to the front of the coach, etc.

i read somewhere that the sensor in the thermostat was thought to control zone 2. then i read another place that it controled zone 1. external wiring needs to connect the correct zone in the thermostat and wall to the correct physical heat and ac zone units.

i guess I could jusr artificially heat up one of the sensors and see which zones temp indicates on the thermostat to verify correct wiring. (remember, before the new thermostat, my heat and ac for a given area were not on the same zone. the micro air thermostat corrected that.}
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