Community Forums

base341 · 07-05-2020, 09:44 PM

Hi all.
I have an Executive with 3 15000 BTU Duo Therm heat pumps.
When the rear one tries to start the compressor, it blows the circuit.
Even the Generator cannot start it. Also a strange smell coming out of it.
I'm assuming I'm going to need to replace the unit.
Is there any chance of just replacing the compressor?
Any help would be appreciated.

8.3Oilbuner · 07-05-2020, 10:18 PM

Good evening Base341; Just recently there has been a lot of A/C discussions here in the forum. First, I doubt that just trying to replace the compressor is an option, just my thought. A new unit would be a better way to go. Not speaking from experience, but there have been discussions here about the roof A/C's having the start capacitor's fail in the A/C unit. From what I have read some say it does not cost that much to replace the capacitors and is not a complicated job. You need to read how to deenergize them so not to set your hair on fire. I am sure someone with more experience with the situation you described will respond. Try using the search box at the top right of this page for the problem you have described and you should find other posts about problems with A/C units not starting the compressor. Sorry, that's all I can of this evening. Hope this info helps!

jacwjames · 07-06-2020, 06:06 AM

What kind of amperage are you seeing when you just try to run this AC unit. You can start the generator and see it on the load center. What is it when the fan first starts and then when the compressor kicks in?
I was having trouble with my front AC unit, it started to pull higher amps with the fan and sometimes would kick the breaker when the compressor kicked in. I finally crawled on the roof and removed the shroud to check things out. I found that the fan motor was almost froze up, could barely turn it over with my hand. Found a replacement and changed the motor which solved he problem. Cost was ~$120 for the motor. If you pay a repair shop to do this it probably won't be economic but is a DIY type job,

onechaddude · 07-06-2020, 06:14 AM

Quote:

Originally Posted by base341

Hi all.
I have an Executive with 3 15000 BTU Duo Therm heat pumps.
When the rear one tries to start the compressor, it blows the circuit.
Even the Generator cannot start it. Also a strange smell coming out of it.
I'm assuming I'm going to need to replace the unit.
Is there any chance of just replacing the compressor?
Any help would be appreciated.

I believe Oil burner hit the nail on the head. My rear AC did that several years ago. We were camping and awoke to the burning smell I'm sure the same as you smelled. Long story short, the compressor capacitor took a dump. Had a new one overnighted to the campground and we were back in business. Like Oil burner said, make sure you denergize it before you handle it. Good luck.

Chad

**Spdracr39** · 07-06-2020, 06:36 AM

I third the capacitor diagnosis.

hypoxia · 07-06-2020, 06:46 AM

Quote:

Originally Posted by base341

Hi all.
I have an Executive with 3 15000 BTU Duo Therm heat pumps.
When the rear one tries to start the compressor, it blows the circuit.
Even the Generator cannot start it. Also a strange smell coming out of it.
I'm assuming I'm going to need to replace the unit.
Is there any chance of just replacing the compressor?
Any help would be appreciated.

Burnt electrical smell? PTCR frequently does that and is mounted on a capacitor which are the first suspects. Measure the capacitance with a meter or just replace them with non-Chinese parts. While there clean the coils.

CountryB · 07-06-2020, 06:47 AM

Try starting the rear AC unit by itself (with middle and front units Off) while on shore power. If the AC unit hums but doesn't start then it is most likely the "start capacitor" but if it still trips the circuit breaker, then you may have a wiring issue (shorted wire, etc.). The circuit breaker should not trip on a bad capacitor.

base341 · 07-06-2020, 07:24 AM

Thanks for the suggestions.
I think the start capacitor is at least worth a try since they are pretty cheap and look to be pretty easy to change.
The fan itself runs fine, I just assumed the compressor was frozen up or something, the capacitor fail makes sense.
I love this place

DFord · 07-06-2020, 10:41 PM

Start capacitors are only good for so many starts per hour (less than one a minute). They should only be in the circuit for less than a second during compressor start-up. They overheat easily and that could be what you're smelling. Get up on the roof and take the cover off to examine what things look like. Another common failure is the ends crimped on the wires for the spade connectors. Check all of them. Pop the cover off the compressor terminals and make sure none of the connectors look burnt. Same for the capacitors. The start capacitor will probably be a round Bakelite plastic and the run capacitor will be in a metal can. Both should have their electrical ratings written on the sides. The replacements may not look identical but the electrical ratings should be the same.

DFord · 07-07-2020, 11:49 AM

VERY IMPORTANT; I forgot to mention the "start relay". (It may not be a real relay in these days of solidstate devices.) It should be replaced whenever the start capacitor is replaced. If it malfunctions and leaves the start capacitor in the circuit too long it will ruin the start capacitor in a few seconds. Don't risk it, they aren't that expensive.

base341 · 07-16-2020, 08:17 PM

Well I've been trying for 2 days to find the right capacitor.
I need a dometic or similar 370v 50/15 and there's literally none for sale in the country right now that I can find. Some places show they have stock but don't.
I did find a 370v 50/10 and ordered a couple of them to try. Hopefully it won't make much of a difference. I also ordered a replacement hard star capacitor.
Wish me luck

DFord · 07-16-2020, 09:32 PM

You're ordering the "run" capacitor. You may not need it unless the old one shows signs of bulging. It can be tested with a meter but you'd probably need to order one of those too - everybody doesn't stock them. The 50mfd side takes care of the compressor and 15mfd side takes care of the fan motor. You should be able to get by with the 50/10 but I'd keep looking in earnest for the correct replacement. I think the start kit is really what you need. Wasn't there one on it to begin with? The tightwads may be saving a few bucks these days by trying to get by without them but they are a must for RV air conditioners.

wamcneil · 07-17-2020, 04:11 PM

I recently had a capacitor failure. Here's the dual capacitor I bought:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Did you confirm that it's the capacitor? Somebody mentioned a humming. When my capacitor failed, there was a lot of humming before the breaker popped.

Couple-years ago I had a control board fail in one unit with similar symptoms. A relay apparently fried and it would just trip the breaker.

Cheers,
Walter