COLEMAN MACH DUAL AC BOTH MALFUNCTIONING

[AGENT86]

I require some advice/help. My friend has a 2021 Keystone Montana 373RD 5th wheel. The bedroom ac unit will come on, just the fan. The compressor won't work. Also, the fan will not turn off. Even with the thermostat ( Airxcel 9430A340)turned off, the fan runs constant. The main ac unit has now begun running all the time, even with the thermostat turned off. The only difference is that the compressor is working BUT, the compressor also remains on all the time. The only way to shut the units down is at the breaker box.

While I was trying to see if I could shut the main unit down by raising the temperature setting on the thermostat (Airxcel9630A336) I observed a puff of gray smoke come out from the thermostat back. I could smell a burnt electrical odor. Upon removal of the back cover, I didn't see anything that looked burnt/bad. I get 13.6 volts on the supply (red) wire on the main thermostat. On the bedroom thermostat the power supply is not on the red wire, it's on the blue or yellow, I forget at this time.

I disconnected the green wires at the main thermostat but it made no difference. When I disconnected the red power wire the unit shut down, which is no indication of anything, really? So, without digging any deeper for now, replacing both thermostats seems to be the first course of action? Yes, no?

One other note. Last year when he bought the trailer the first week he used it there was a power loss issue that caused most of the outlets to not work. After diagnosing to the best of my ability, I determined the bathroom GFI outlet was defective. I replaced it with a high quality GFI and then, discovered a second defective GFI in the basement. I replaced it as well & everything worked as it should until, last month. When they arrived for a week, the refrigerator was out. It runs through a harness into the basement. I found some outlets inside that were dead, which once again turned out to be the fault of the basement GFI. It had tripped at some point. It would not reset. I installed another new GFI and it's been working fine since.

We've had a LOT of massive thunderstorms these past few months. I'm wondering whether close, or even direct lightning strikes are responsible for the GFI issues and possibly the AC issues? IDK. I do know that the original GFI outlets that came with the trailer are pure garbage. One final question: Can I replace these Airxcel digital thermostats with same brand analog thermostats?

ANY advice/help would be much appreciated!

 

[Kirk]

Each air conditioner should have a cricuit breaker on the 120V distribution panel that will turn off the associated air conditioner. That would be a good place to start.

 

[8Muddypaws]

Letting the magic smoke out of anything electrical is a bad thing. You're going to need a new thermostat. You may be able to use a house one, maybe not. When I changed thermostats I had to re-wire the AC units.

 

[AGENT86]

Each air conditioner should have a cricuit breaker on the 120V distribution panel that will turn off the associated air conditioner. That would be a good place to start.

Yes. That's how I shut them off. The breakers wouldn't have anything to do with the actual unit not shutting down when it's supposed to or the compressor not turning on/off. Or am I mistaken?

Letting the magic smoke out of anything electrical is a bad thing. You're going to need a new thermostat. You may be able to use a house one, maybe not. When I changed thermostats I had to re-wire the AC units.

To clarify, when I was "adjusting" the thermostat, what I meant is that I was simply pushing the up/down buttons to change the temperature setting. I will clarify that with some editing in my original post. However, you are correct. That thermostat is toast. I'm thinking both thermostats are/were defective. When you say you had to re-wire the AC units, do you mean just at the thermostat or all the way back to the unit as well?

I will say, many of the wires do not match the indicated color on the back of the thermostat. It probably doesn't matter as the units were functioning properly for a while, anyway. IDK.

 

[CharlesinGA]

GFI's do have electronics in them, so its possible they got hit. Is the fridge a compressor fridge or a absorption unit. In either case, having the fridge on a GFI is not good, as you can easily have a whole lot of food ruined if the GFI trips. If an absorption unit, it should simply switch over to gas and keep running. The good thing about having an absorption fridge on a GFI is that the heat element can internally short, not enough to blow the breaker, but enough to cause a "hot skin" condition. The GFI will stop this. Not a common occurrence but it can and has happened.

Charles

 

[AGENT86]

GFI's do have electronics in them, so its possible they got hit. Is the fridge a compressor fridge or a absorption unit. In either case, having the fridge on a GFI is not good, as you can easily have a whole lot of food ruined if the GFI trips. If an absorption unit, it should simply switch over to gas and keep running. The good thing about having an absorption fridge on a GFI is that the heat element can internally short, not enough to blow the breaker, but enough to cause a "hot skin" condition. The GFI will stop this. Not a common occurrence but it can and has happened.

Charles

It's a compressor fridge. It came from the factory wired as it currently is. The fridge is in a slideout & doesn't plug into a traditional type outlet. The wires run through a heavy cable/harness and then into the basement. I haven't traced exactly where. I'll have to do that sooner or later.

Good info about the absorption style fridge. I have one in my unit. I'll have to install a GFI outlet for a little more peace of mind.

 

[8Muddypaws]

I actually had to change the control box at the air conditioner end. It was about 18 years ago so I have no more details.

 

[Kirk]

I'm thinking both thermostats are/were defective.

While the thermostats are typically where you turn an air conditioner on or off, it seems starange that 2 of them located in different areas would both fail at the same time. The one that you smoked is no doubt bad now, but I would be just a little bit suspicious of them both failing at the same time. I agree that the problems were not caused by the circuit breakers since the only thing that they do is to remove power. It would help some if we knew which Coleman units they are. You can throw parts at them and you might get lucky, but it would be more likely to work if you did some troubleshooting first. Here are a couple of service manuals but there are several others.

Service manual, 6700, 7000, 8000, & 9000
Service Manual Mach 8

 

[AGENT86]

While the thermostats are typically where you turn an air conditioner on or off, it seems starange that 2 of them located in different areas would both fail at the same time. The one that you smoked is no doubt bad now, but I would be just a little bit suspicious of them both failing at the same time. I agree that the problems were not caused by the circuit breakers since the only thing that they do is to remove power. It would help some if we knew which Coleman units they are. You can throw parts at them and you might get lucky, but it would be more likely to work if you did some troubleshooting first. Here are a couple of service manuals but there are several others.

Service manual, 6700, 7000, 8000, & 9000
Service Manual Mach 8

The units both say Coleman Mach Q on the covers & the rear unit has a sticker:
Mach 15 Power Saver Heat Pump
Model# 48009-9694
Serial# 210175983

I would tend to agree, that it seems strange for both thermostats to fail at the same time. Actually, the bedroom unit malfunctioned first. The main unit was operating OK for close to a week after that. So, while not the same time, but, still close.

 

[John From Detroit]

The Thermostat gets power from the furnace.. The furnace has a fuse or circuit breaker... Power comes in on one of the Blule wires (The other tells the furnace to furn.

 

[chickenfoot]

There was a bad batch of these units a couple years ago. Brand new from the factory the compressors had a tendency to freeze. The fan would still blow but they wouldn't get cold. Coleman was replacing them under warranty, but the wait to get them was getting fairly long because parts.

 

[AGENT86]

UPDATE....FIXED!
Well, sometimes it's just what it seems. Both thermostats arrived this week. I installed them & BOTH AC units now function perfectly in all modes. Just like the two GFI receptacles that were faulty last summer, so were both thermostats. I really think it's just a bad batch of china made garbage. We bought two of each of the thermostats so as to have a spare for each unit.

The two thermostats are different. The main unit is heat & cool and the wires slide into the back & lock in place. The bedroom is cool only & the wires are soldered directly to the circuit board & splice into the wires coming through the wall.

I want to thank all who offered their input in response to my post.

 

[Kirk]

UPDATE....FIXED!

Thanks for updating all of us! While there may be no connectin to the two failing at the same time, I would give that some thought just in case you can determine a reason to avoid the same happening in the future.