FIXED ???? Roof AC Starts...Stops...Then Run Fine

[Bill_Diana]

During our final trip for 2021 in October we had a few days the air conditioning was needed. The air conditioner would start and then run for about 5 seconds and shut down. Both the fan and compressor were starting as usual except shut down after about 5 seconds. Then about 10 to 15 seconds later the air conditioner fan & compressor would again start and this time would run normal until the thermostat temperature was satisficed. Cooled just fine.

The next time the thermostat called for cooling the same sequence would take place. Start...run about 5 seconds...stop for about 15 seconds...then start and run just fine.

This is a Duo-Therm by Dometic 595 series 15,000 BTU unit. Any ideas on what would cause this sort of behavior?

Thanks for taking the time to read and thanks in advance for your ideas & comments.


UPDATE TODAY MAY 15,2022

The motorhome has been in winter storage for the past few months and during that time I've been pondering how I could fix the AC issue.

Now this is going to sound crazy, but here it goes. When waking up one February morning the quartz time clock in the living room was performing properly. It would only play part of the song on the hour and then quit. I didn't know what to do, so lacking any solution I thought I would change the C cell batteries. Clock started working perfectly again.

Then it struck me. Maybe I should change the AA batteries in the motorhome thermostat for the air conditioner.

Today is our first trip for the 2022 season. As soon as we arrived at Country Acres Campground, Lancaster, PA.....I was extremely anxious to replace those old AA's with fresh AA's. When installing batteries I always mark the date on the battery with a Sharpie pen. These old AA's had a 4-2018 date.

Guess what? The air conditioner is working just fine. So, could it be possible it was only old batteries in the thermostat causing the problem? I have my fingers crossed and hoping the AC keeps working on the 10 day trip.

Again, thanks to all of your for your help & suggestions, You folks are the best !!!

[Bill_Diana]

Scroll to the first post at the top to read an update. Seems the issue has been resolved.

[Bill_Diana]

dougrainer wrote:
Capacitors are cheap. If you have 2 units swap them. see if the problem follows the capacitor. If not, just buy a start capacitor and install it. Doug

Thanks Doug for the great suggestion. I'll not be able to attack this problem till the weather warms in April.

[dougrainer]

Capacitors are cheap. If you have 2 units swap them. see if the problem follows the capacitor. If not, just buy a start capacitor and install it. Doug

[Bill_Diana]

dougrainer wrote:

Bill/Diana wrote:

Heisenberg wrote:
Loose stabs on the compressor capacitor.

I suspect the problem is somehow related to the capacitors. What are loose "stabs"?

The spades of electrical connectors also known as pins. Doug

Thanks for the clarification Doug. For me the capacitors are prime cause for this issue. I do not know that for a fact, just a suspicion on my part.

[dougrainer]

Bill/Diana wrote:

Heisenberg wrote:
Loose stabs on the compressor capacitor.

I suspect the problem is somehow related to the capacitors. What are loose "stabs"?

The spades of electrical connectors also known as pins. Doug

[Bill_Diana]

Heisenberg wrote:
Loose stabs on the compressor capacitor.

I suspect the problem is somehow related to the capacitors. What are loose "stabs"?

[Heisenberg]

Loose stabs on the compressor capacitor.

[dougrainer]

All RV electronic controlled systems have a 2 minute 45 second time delay on restart of the compressor. This is to allow time for the pressure in the system to equalize to allow easier start up. I would use compressed air to blow out the wall tstat. It may just have accumulated dust and debris on the electronic circuits of the Tstat. I would also check the upper wiring on the AC unit for loose or burnt wire connectors. Doug

[time2roll]

I would assume it is something in the thermostat or control box. Good time to go digital if your system has analog controls.

[Bill_Diana]

2oldman wrote:

Bill/Diana wrote:
Once Spring arrives I'll be sure to update this topic with the solution.

Good. One thing I find odd, or at least a lot different from mine, is that if my compressor starts up but its power is interrupted by anything like the generators failing to start it, it will not restart for at least 5 minutes. I guess it's resetting something.

I understand what you are saying. If I lower the thermostat immediately after the compressor shuts down, there is always a delay before the compressor kicks in. This is normal.

[2oldman]

Bill/Diana wrote:
Once Spring arrives I'll be sure to update this topic with the solution.

Good. One thing I find odd, or at least a lot different from mine, is that if my compressor starts up but its power is interrupted by anything like the generators failing to start it, it will not restart for at least 5 minutes. I guess it's resetting something.

[Bill_Diana]

Thanks everyone for taking the time to submit your ideas and thoughts about this AC problem. Hopefully I'll receive some more input.

Once Spring arrives I'll be sure to update this topic with the solution.

[dougrainer]

2oldman wrote:
"Your air conditioner may be short cycling because it is repeatedly starting up then overheating (and shutting down) due to a bad compressor, dirty filters, dirty coils, low refrigerant, or frozen coils. An overcharged system will cause liquid Freon to get into your compressor and cause it to malfunction"

NONE of this will be responsible for his problem. ANY of these problems will not manifest itself in the few seconds the malfunction happens. Doug

[2oldman]

"Your air conditioner may be short cycling because it is repeatedly starting up then overheating (and shutting down) due to a bad compressor, dirty filters, dirty coils, low refrigerant, or frozen coils. An overcharged system will cause liquid Freon to get into your compressor and cause it to malfunction"