Roof A/C Issue

[joraz]

Class C with a 13.5 Dometic (Model Number: 520316.506E) year 2009


My rig is parked at the house in the hot Arizona sun. The A/C works fine for most of the day but when the ambient temp hits 104 or so the compressor shuts down and the fan blows hot air.

The A/C has had little use over the years. I cleaned both the evaporator and condenser coils although both were already very clean.

The unit is draining as it should and the interior filters are clean.

I did a voltage check over the day yesterday and have eliminated low voltage as the problem.

I have been advised on another forum that the issue could be the overload protector (thermal switch) which is designed to shut down the compressor when it's too hot. So I figured I would just replace it. Problem is that it looks to be internal to the compressor.

Any ideas? Thanks.
jor

Compressor Photos

[dougrainer]

joraz wrote:
OP here. All fixed and blowin' cold. The solution turned out to be simple and at the best cost - free. After searching for capacitors, thermistors and thermal overload switches, I simply reset the Dometic 5-button and whadayaknow, success! Thanks to all. I now know a lot more than I did about that roof a/c!
jor

HAPPY THAT IT IS RUNNING. But, doing a 5 button(or 10 button) reset does NOTHING to fix your problem. ALL a Dometic reset does is verify the DIP switch settings on the upper control board. Nothing else. Please post if the original problem comes back. Doug

[joraz]

OP here. All fixed and blowin' cold. The solution turned out to be simple and at the best cost - free. After searching for capacitors, thermistors and thermal overload switches, I simply reset the Dometic 5-button and whadayaknow, success! Thanks to all. I now know a lot more than I did about that roof a/c!
jor

[dougrainer]

joraz wrote:

I need to know if your wall tstat looks like this

No, it's a 5-button Duo-Therm Comfort Center (photo here thermostat).

Speaking of the thermostat, yesterday morning I reset it according to the directions. It got up to 102 or so yesterday and that a/c didn't miss a beat. It's 101 right now and it's going strong.

One other thing, before I reset it, I would turn it on and select cool. There would be a significant delay before the fan came on. Now, the fan starts up right away. Could be this is my problem. Keeping my fingers crossed.
jor

Sorry, Brain fart. I missed 2009. There is a Freeze Thermister that is inserted into the evap. Does your model AC have the inside removable air filter plenum cover? If so, make sure that thermister is inserted into the evap. Doug

[joraz]

I need to know if your wall tstat looks like this

No, it's a 5-button Duo-Therm Comfort Center (photo here thermostat).

Speaking of the thermostat, yesterday morning I reset it according to the directions. It got up to 102 or so yesterday and that a/c didn't miss a beat. It's 101 right now and it's going strong.

One other thing, before I reset it, I would turn it on and select cool. There would be a significant delay before the fan came on. Now, the fan starts up right away. Could be this is my problem. Keeping my fingers crossed.
jor

[dougrainer]

I need to know if your wall tstat looks like this? Doug

https://www.dometic.com/en-us/outdoor/climate-and-comfort/air-conditioners/air-conditioner-accessori...

The reason is simple. Even tho your RV is 2009, years ago Dometic had thousands of single Zone tstats that had a SIMPLE fault. If the interior of the RV was over 95 degrees, then the tstat failed to function. The only fix was a new updated Tstat which removed the heat failure problem. A way to test this was to take a PC air can, turn upside down and spray the cold on the tstat for a few seconds. If the Tstat and system functioned the tstat was your problem.

[joraz]

Here is a parts list

Thanks a million!
jor

[enblethen]

Here is a parts list and link to parts breakdown.Parts list and breakdown

[joraz]

That is a dual capacitor.

Thanks for the explanation.
jor

[prichardson]

That is a dual capacitor. The 60uf side is for the compressor and the 12.5uf side is for the fan motor.

[joraz]

After taking in all the comments I think I'll replace the start and run capacitors and the thermistor just in case.

I had intended on jumping the thermostat wires today but it's just a circuit board. Anyhow, I did reset the thermostat and it's running fine now with 101 degrees outside.

Now the problem. I found a start capacitor with matching numbers here: start

...but I am confused about which run capacitor to get. I have four lines of numbers. The last line indicates 60+12.5uF and 370 volts so I guess that 12.5 is the capacitance and the 60 maybe the frequency? Anyhow, this one looks like it could be it: Run

I'm just out of my area here. Thanks.

I've linked to a photo of my capacitors here: capacitors
jor

[dougrainer]

enblethen wrote:
Doug:
Post part number for the OP

I lack the time to research. It is VERY EASY to get the Numbers off the existing capacitor/s and order from Amazon. The Part is less than $30. Very easy replacement. Doug

[wildtoad]

I too suspect a capacitor failing when it gets too hot from direct sunlight.

[enblethen]

Doug:
Post part number for the OP

[dougrainer]

Replace the Start capacitor. Doug