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

Bill_Diana
Explorer
Explorer
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 !!!
18 REPLIES 18

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

Bill_Diana
Explorer
Explorer
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
Nomad
Nomad
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
Explorer
Explorer
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
Nomad
Nomad
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
Explorer
Explorer
Heisenberg wrote:
Loose stabs on the compressor capacitor.



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

Heisenberg
Explorer
Explorer
Loose stabs on the compressor capacitor.
2013 Winnebago Sightseer
2017 Colorado

dougrainer
Nomad
Nomad
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
Explorer II
Explorer II
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
Explorer
Explorer
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
Explorer
Explorer
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.
"If I'm wearing long pants, I'm too far north" - 2oldman

Bill_Diana
Explorer
Explorer
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
Nomad
Nomad
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
Explorer
Explorer
"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"
"If I'm wearing long pants, I'm too far north" - 2oldman

Bill_Diana
Explorer
Explorer
MFL wrote:
Retired JSO wrote:
If the unit fan is set to auto and is trying to overcome a 3-5 degree temp differential between ambient and thermostat setting, the unit will stop momentarily and change fan speeds


This is a good explanation, as to first use, when differential is too great, while fan set to auto. However, after reaching/cooling to stat setting, fan and compressor should start/run, before temp climbs more than a couple of degrees.

OP...is the inside temp climbing too high, before stat is kicking in? At 20 yso, your stat may need replacement. If the unit cools the RV, like past years, it seems to be doing it's job.

You may want to monitor actual inside temps, with a known good digital thermometer. If the stat seems to be the culprit, I'd run fan continuous at high setting, until stat repaired/replaced.

Jerry


Thanks for the reply Jerry. I replaced the thermostat about 5 years ago. The AC never behaved this way before. The thermostat has a High/Low switch for the fan.

I'm in the northeast, so the motorhome is resting in storage for the winter months. I won't have the opportunity to test the AC again till the April/May timeframe. For now I'm trying to get some ideas on what and how to troubleshoot. Thanks again for sharing your knowledge.