Coleman AC compressor won’t start

[mxdad777]

I have a 2018 5th wheel with a roof top Coleman Mach model # 48254C869. When I turn on the Thermostat the fan runs but when the compressor tries to start it hums real loud for about 1 to 2 seconds and then shuts off. It will try to start about every minute or so, but it only hums and then shuts off. I suspected the start capacitor, but I checked it and it is testing good. It is rated at 60uf +/- 5% and it tests at 60.3. I also only found two start capacitors, one for the fan and one for the pump. Shouldn’t there be a run capacitor too? Any ideas what else I might check?
Also while I was up there I put my hand on the fan motor and it was so hot to the touch it would have burned me if I left my hand on it for more than a second or two. Is this normal for the fan motor to be this hot to the touch after running less than 15 minutes?
I own a tool repair shop so I know my way around most things, but I’ve never messed with any AC units. Any help will be much appreciated.

[bigfoot84]

@mxdad777,
What was the solution to your problem below? I suspect you had to replace the unit or at least the compressor. My AC draws 40A for the 2 seconds that it does come on before shutting off.

When I turn on the Thermostat the fan runs but when the compressor tries to start it hums real loud for about 1 to 2 seconds and then shuts off. It will try to start about every minute or so, but it only hums and then shuts off.

[mxdad777]

Stupid me!! I understand household electricity like the back of my hand. I obviously DON’T understand RV power. I didn’t realize that RV 30amp outlets were only 120v. When I plugged my trailer into my 30amp 240v welder outlet and used the RV 30-50 adapter, I sent 240v down the one buss bar. The AC unit was running off 240v instead of 120v. I also fried the GFCI outlet (that’s a cheap fix) but now I have a refrigerator that’s not working. Time to dive into that and hope I didn’t fry the fridge. I’m hoping to find a blown fuse or something. The AC unit seems to have survived and is running perfect. The fan motor is cool to the touch and the compressor kicks right on and runs like a champ. Anyway, another live and learn lesson about these darn RV’s we love so much.

[dougrainer]

No it is not normal for the Fan motor to be that hot. THAT points to a defective capacitor. I rarely test capacitors. It is quicker and easier to just install my test capacitor. Since you have 2 problems, as Chris mentioned, line voltage can be an issue as well as the Capacitors. A HARD START kit is designed for compressors not Fan motors. Since you have a problem also with the fan motor, a Hard Start kit will not fix that. BUT, installing a Hard Start kit for the compressor is a good idea anyway. Doug

[Chris_Bryant]

What’s the line voltage? Where is it plugged in?

[DFord]

Like I said, they used to be standard on RV air conditioners. They allow the compressor to cycle under load and give it a tremendous boost in power to get started. Bean counters and cheapskates probably deleted them from the newer units.

[mxdad777]

DFord wrote:
It might be worth trying a "start kit" on it. They used to be standard equipment but I'm pretty sure they're not anymore.

It’s funny you mention this. I just found a schematic for my unit and it lists a “start device package” as one of the components. (Part # 8333A9021 Start Device Pkg. (includes start capacitor and PTCR device). My compressor doesn’t even have this part on it. Weird! Why would it be listed on a parts schematic and not be used on all units? Well anyway, I found one on Amazon and it will be here Monday. I’ll install it and hopefully that fixes it.

[DFord]

It might be worth trying a "start kit" on it. They used to be standard equipment but I'm pretty sure they're not anymore.

Coleman-Mach Start Device Pkg
https://arvrepair.viaretailparts.com/69-1260

http://www.arvparts.com/coleman_mach_48254C869_parts.pdf