Another Coleman Mach AC question

Armydave · 07-14-2022, 06:39 AM

Hello again friends,

So, let me start by saying I am pretty handy with most repairs. However, when it comes to heat and AC I know how to turn it on and off. So once again I need advice from those with more experience than I. LOL

Yesterday I noticed the temp in the motorhome starting to climb. Both A/C's were running, so I thought. Turns out only the fan was running on my bedroom a/c. Once I figured it out, using the thermostat, i turned that a/c off and then back on. The compressor did not kick on. Did that a few times with no luck. Then not knowing anyrhing else to do, I turned off the main breaker off and back on at the fuse box. Turned the a/c back on and the compressor started. Has ran great all night starting and stopping on its own.

Are there services that need to be performed? I had heard that these are closed systems and you have to replace the entire unit if there is an issue.

Thanks again,
Dave

Ford1 · 07-14-2022, 12:46 PM

Since it did eventually come back, my guess would be a dirty electrical relay contact. The compressor current draw can cause the contacts to deteriorate over time and they might be cleaned up ( burnished, if not badly burned) or replaced. Unless you are really familiar with electrical/electronic components and circuits, you might want to leave it up to a professional. Most of the contactors are soldered onto the A/C control board.

Armydave · 07-14-2022, 02:16 PM

Thanks for the info Ford1. I will definitely let a pro do that if needed.

Dave

Lv2Roam2 · 07-15-2022, 06:26 AM

As you work through the diagnostics also consider 1) t-stats sometimes need a '12V reset' to operate properly (looks like you did that on the 120 VAC side - may need the same on the 12VDC side), and 2) a starting capacitor may be going bad...

Share what results - we all learn...

eaglelen · 07-20-2022, 04:37 PM

The compressor will turn off if the unit freezes up in high humidity. There is a freeze sensor "stuck" in eval coil visible from inside that can go bad. It's job is to cycle the compressor to defrost the system. If it happens again, I'd look at that. Running the fan on low in high humidity can also cause freeze up, which takes 20-30 minutes to thaw.

jerichorick · 07-20-2022, 06:36 PM

Quote:

Originally Posted by eaglelen

The compressor will turn off if the unit freezes up in high humidity. There is a freeze sensor "stuck" in eval coil visible from inside that can go bad. It's job is to cycle the compressor to defrost the system. If it happens again, I'd look at that. Running the fan on low in high humidity can also cause freeze up, which takes 20-30 minutes to thaw.

I'm with you on this one. Very common problem. Cleaning the coils might help some. I remove the shroud and hose off the coil. As far as the cooling coil goes, I open the plenum box and brush it off. I have put pipe insulation on the pipes around the compressor to the coils. That seems to help also.

Americanrascal · 07-21-2022, 06:05 AM

In addition to all the good advice given here, I'd add one more check. That being the high pressure switch/valve. We could not get the compressor to come on and after days of bird dogging the problem, I had an A/c tech come by and he traced it down.

As the system is sealed the choice was to open the system, drain it remove the valve and install a new pressure valve and Shrader valve to restore the system. But as it was 6 years old the extended service company said to just replace the entire unit.

Actually the replacement of the whole unit itself once on the roof was very easy and only took about 20 minutes. Most of the time was using the lift to get the old one down and lifting the new unit.

I stripped and salvaged everything I could from the old unit for future repairs.

Armydave · 07-21-2022, 01:39 PM

Thanks for all the help everyone. I had more issues after posting this thread. We are in Arkansas where the humidity and temperature have been insane!

After posting my initial thread the AC froze up. Stopped producing condensation or cool air. I reluctently climbed on the roof, because I couldn't get a RV rech to call back. Anyway, it was froze solid. I took off the shroud and the cover for the evaporator coil. I allowed it to thaw and cleaned the coils a little bit but they looked good. I replaced the insulation over the coils and sealed it back up. Started working great.

Then I did some research on what makes them freeze up. I had purchased RV filters from "Filter Time". When I checked my return filters they were very dirty. I think the AC was not getting enough return air to work properly. It had only been 2 months since I replaced them but now I know to check more often. I would not recommend those filters for the Coleman Mach systems. I don't think the allow enough air flow. I replaced them with "RV AIR" filters.

Temp has been between 95-100 with heat index of 110 some days. Has been running strong and cooling. My lesson learned was keep an eye on those filters. For those that are not full-time I'm sure you can streach that time out between filter changes.

Again, thanks for all the help. Im sure I'll have more question.

Dave

buckeye · 07-21-2022, 02:07 PM

Quote:

Originally Posted by Armydave

Hello again friends,

So, let me start by saying I am pretty handy with most repairs. However, when it comes to heat and AC I know how to turn it on and off. So once again I need advice from those with more experience than I. LOL

Yesterday I noticed the temp in the motorhome starting to climb. Both A/C's were running, so I thought. Turns out only the fan was running on my bedroom a/c. Once I figured it out, using the thermostat, i turned that a/c off and then back on. The compressor did not kick on. Did that a few times with no luck. Then not knowing anyrhing else to do, I turned off the main breaker off and back on at the fuse box. Turned the a/c back on and the compressor started. Has ran great all night starting and stopping on its own.

Are there services that need to be performed? I had heard that these are closed systems and you have to replace the entire unit if there is an issue.

Thanks again,
Dave

I had a similar problem, without going into all the details. I was told by
a Winnebago Rep. to replace the breakers or tighten the screws on the breaker. I tightened the screws and had no more problems. By the way one
of the pros didn't check those when I took it back to the dealer, he told me nothing wrong with the AC