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Old 08-22-2021, 06:08 PM   #1
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Coleman Mach A/C Troubleshooting

I have a 2019 Minnie Winnie 31G with a Coleman Mach 15,000 BTU AC, Model # 48254C869. On my most recent trip I wanted to exercise the generator on the way to the campground. After turning on the generator I turned on the AC at the thermostat and the fan did not come on. After a few seconds I shut it off and retried and still nothing. Once it sounded like the compressor fan turned on but no impellor or distribution fan. I tried just turning the fan on manually also but nothing. I shut the generator down and drove to the campground about an hour away. After setting up I tried the AC again, no fan. I took the inside cover off and checked wiring, everything looked fine. When I was opening up the cover on the cold side the system started up. I let things cool down in the camper while checking things on the roof, everything looked and sounded fine. I cycled the system a few times and everything was fine. The system worked fine the rest of the weekend. When I got home I took the roof shroud off and looked around. The capacitors looked fine to me and wiring seemed fine, see attached pictures. Does anyone have a obvious solution or troubleshooting procedure to help me along?
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2019 Minnie Winnie 31G
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Old 08-28-2021, 09:11 AM   #2
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I tried again today after not using ac for a week. I started up the generator, let it run for about 5 minutes, then tried turning on the circulating fan only and nothing. I let it sit like that for about 4 minutes then the fan came on. I turned on ac and let it run for about 5 minutes then shut it down. I was able to cycle the fan on and off without any problems. Can anyone give me some advice?
Is this normal? Is it a sign of the fan going bad?

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Old 08-28-2021, 09:33 AM   #3
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This sounds more like a thermostat or control board problem. I would start with the t-stat first.
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Old 08-31-2021, 05:19 PM   #4
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One of the (3) Coleman Mach units in my Tiffin does this same thing. At times it runs fine, blower fan comes on and in a little while the compressor comes on. Other times, the compressor will come on, but the blower fan hasn't and doesn't start up.

The other two units do not have this issue. Is there a separate thermostat or controller other than the one control/thermostat that handle all three units?

I use the unit when I'm present, but I always listen to see if the fan comes on or only the compressor and if the fan doesn't come on, I lower the thermostat to shut down the compressor. Any ideas or thoughts?

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Old 08-31-2021, 07:00 PM   #5
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I just have one unit in my Class C. I changed the thermostat a couple years ago to a Honeywell RTH5100B 1025 Deluxe Manual Thermostat and it has been working fine. My next step is to reinstall the original Coleman Mach thermostat, when I find it.
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Old 09-17-2021, 07:13 AM   #6
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I could not find the original thermostat so I am still using the Honeywell model. At home I was checking wires and connections and found the wire bundle going to the thermostat was hanging without support inside the wall. While securing the bundle the white wire which goes to the furnace pulled out of the crimp connector. After installing a new connector I put everything back together and tried the fan numerous times and it worked fine. I am presently in the middle of a week long trip and the fan quit again. I was able to check the wire and pin going into the control box for the high speed fan and was getting 13.7 volts but fan was not running. I switched the wire coming from the thermostat for the fan to the pin for the low speed fan and the fan worked. I’ve been running that way for a couple days without any problems.
So I guess my control box is the problem or the relay for the high speed fan.
Can I get some guidance on my control box theory? If I am correct is it worth trying to replace the relay or just replace the control box?
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