Community Forums

Fmiclon · 08-04-2024, 06:30 AM

We just bought a used Qwest 24L and on our maiden voyage across the country from Arizona to Connecticut the coach roof A/C worked for the first few days and then when we tried it at our next campground it would not get cold. Any suggestions on where to start for troubleshooting? I have tried it connected to several different power sources and checked the AC breaker.

Was thinking it could be the thermostat - we have one with a sliding temperature setting. The fuse inside appears to be okay.

The coach only had 30k miles and is a 2019 with a Coleman Mach A/C on the roof.

Thanks in advance!

Fred M.

craigd853 · 08-04-2024, 07:22 AM

Quote:

Originally Posted by Fmiclon

We just bought a used Qwest 24L and on our maiden voyage across the country from Arizona to Connecticut the coach roof A/C worked for the first few days and then when we tried it at our next campground it would not get cold. Any suggestions on where to start for troubleshooting? I have tried it connected to several different power sources and checked the AC breaker.

Was thinking it could be the thermostat - we have one with a sliding temperature setting. The fuse inside appears to be okay.

The coach only had 30k miles and is a 2019 with a Coleman Mach A/C on the roof.

Thanks in advance!

Fred M.

Hello, a couple of questions for you. First was the thermostat switch set to auto or on? If it was set to on the fan portion of the a/c will run 24-7 and the compressor will only come on when the temp gets to the thermostat setting you have preselected. Make sure switch is in the auto and the other switch is on a/c mode and turn the thermostat down into the 60 degree range and see if the compressor kicks on along with the fan. Report back your findings and others can offer suggestions once we make sure your settings are where they need to be. Good Luck

Fmiclon · 08-05-2024, 06:01 AM

Thanks for your response! The first three nights of our trip we set the “System” switch to Cool, and the “Fan” switch to High with the thermostat at about 65. It blew cold air and in the morning we were nice and frosty. The fan did stay on all the time and I assume the compressor cycled as necessary.

The fourth night as soon as I turned on the unit we noticed the air was not blowing as cold. I couldn’t tell if the compressor was cycling on or not.

I have tried it in various settings with no better results. Last night we left it on in the Fan mode on low speed so we had air movement. It isn’t that hot at night here in Connecticut, so we were comfortable. After reading your post this morning I switched it to the Cool mode and right away we could hear the difference in fan speed when it sounded like the compressor kicked in. It is blowing cool air, but it is cool outside - and humid - so it is hard to tell if it is working properly.

I wonder if there was a power issue at the campground that caused some issues with the unit. I normally have a surge protector power monitor on my rigs, but we didn’t have time to buy one and I usually install one in the unit vs one on the power cord. Hopefully that isn’t why it failed. It is a 5 year old unit bit only has 30k miles, so it may not have been used much.

Thanks for your advice and help!

737 Driver · 08-05-2024, 06:43 AM

Do you have a generator on your rig? If so, start it and see if the a/c works. Could be the power pedestal.

Tor
2017 Anthem 44B

Fmiclon · 08-06-2024, 07:29 AM

Tried it, still no joy. Using shore power I did hear compressor kick in, but no cold air. Spoke to a dealer service department guy I know and trust and he said it sounds like a Freon leak. Looking like a replacement unit is in my future.

Fmiclon · 08-07-2024, 05:56 PM

Had a new Coleman Mach 8 15k BTU roof unit installed by a local RV dealers here in Connecticut today.

It was supposed to be a ducted air conditioner-only unit, however the supplier shipped a Model 47004-079 which also has a heat pump. They didn’t even know it was the wrong one until I asked for the paperwork and saw it had the heat pump. They did not charge me any extra for the unit because the supplier did not charge them more.

However, they also did not connect the heat pump, since they didn’t know and they couldn’t have because it would require a different thermostat in order to control the heat pump and the gas furnace as well.

Does anyone have experience with what thermostat I need and if I will need to install a different controller? I haven’t checked the current controller to see if it is heat pump capable or if there is an available wire to the thermostat to support it.

Thanks for any assistance!

PeterFTH · 08-13-2024, 09:20 PM

Once in a while one A/C unit, usually the aft one, will blow cold and then after a variable amount of time blow room temperature. I believe the condenser "ices up" especially in humid very hot conditions. At first I thought I was going to have to a few rounds with Dometic, but after a few hours off I turned it back on and it was fine after that. The other option is it has lost Freon, in which case if it was transferable you should have warranty coverage because these are sealed units and cannot be repaired.

Steve 716 · 08-14-2024, 08:42 AM

There was a time when a roof AC could be repaired or recharged. No longer. Now, other than cleaning and changing the squirrel cage, they can only be replaced. Coleman (and probably others) started using thinner tubing that is prone to leaks and it appears that the compressors they now use are lower in quality than in earlier generation products. (Some refrigerator manufacturers started doing this as well several years ago). If you get more than four years on a current generation Coleman Mach AC, you are fortunate. My coach, when I owned it, has had four Coleman Mach ACs replaced after failing and I have replaced the squirrel cage in two of them, which fortunately is easy and inexpensive to do.

Try removing the housing on all of your ACs and thoroughly cleaning the units. Dirt can cause reduced cooling and that may fix your problem. While you are there, make sure all of your connections are tight and protected.

RV manufacturers generally install cheap manual thermostats. In their defense, house builders do the same thing. It may just me a matter of heading to Home Depot or Lowes or an online RV parts store and buying a better quality digital thermostat. Before doing that, remove yours and note how it is wired so you can match the connections. I replaced the thermostat in the basement of my coach with a Honeywell digital version one year in and have had no basement heating issues since.

Chap1021 · 08-21-2024, 10:16 AM

I understand your roof AC is not blowing cold, but the internal circulation fan works and blows air. I would check the start capacitor and relay for the compressor. This is one of the most common failures of roof air units. You look at the capacitor to see if it is expanded, rounded top, also test the capacitor with a multi meter that reads micro farads. Make sure you short out the capacitor with a screwdriver prior to handling it.

I have had several AC unit fail and it was the start capacitor. Fairly simple and inexpensive to replace.

Another option is to use a soft-start. I had an ac unit fail like yours on my current RV and I just added a soft-start. It takes the place of a start capacitor and is much easier on the whole AC unit and RV electrical system. I put a soft start on all three of my AC units.