Air Conditioner Acting funny??

[Antjaw]

So, was that subject descriptive enough to bring you here? Here is where I am. I go to a RV park with full hookups, which is rare for me as I am a boondock camper mostly. I run the Rear 13,500BTU A/C (2 on board) and somewhere in the middle of the night it starts cycling every 2 minutes. Not blowing real cold air, but still cooling. I replaced ALL capacitors. Completely cleaned unit (Both coils)and NOW this mother blows cold enough to cool the entire coach by itself. I set the thermostat to 70 degrees and it got to 70 no problem (Probably 85-90 degrees outside at night).
I figure it's cold enough, I'm going to set it to 80 degrees, and let it run throughout the next day just for a good test. I set it at 80 (still 70 degrees in the coach at this point) and the unit doesn't shut off., so I bump it up to 90, which is the furthest it goes and it shuts off. I wait a few minutes for the pressure in the compressor to equalize and bump it back down to 80 and it kicks back on. (It's about 72 degrees inside now). I figure I will let it run and see what it does. So about an hour later, I go back in and it's still running, but now it is cycling just like before every 2 minutes. Still at about 71 degrees, but set on 80. I checked the coils. Unit is not freezing up, and I had previously pulled the freeze sensor off of the coils and let it hang through the intake. Any ideas before I replace/swap the thermostat?

[Antjaw]

Swapped the thermostat from the front to the back and fixed the issue. I ordered a new one from Amazon for less than $30 and it came in today. Now that both A/C units have been cleaned (Both condenser and evaporator coils) and new capacitors installed (Supco SPP6 starting cap and GE Genteq 35/5 uf for the Run/Fan)and new insulating foam under the shroud; with both running I can get the coach quickly to 70 degrees inside while 95 outside in direct sunlight. The units are also both MUCH quieter. Not to bad for 16 year old units that have probably never been serviced.

[Antjaw]

It would impact it negatively in the sense that the unit would never shut off it it froze over; however, I removed it from the coils as a troubleshooting method. Since it's function is to shut down the unit if it detects a specific low temperature, I removed it from the coils to see if the issue resolved or not. Had it resolved, I would have known that this sensor had gone bad and was shutting the unit at a higher temperature than it was designed. Since it did not resolve the issue, I know that the sensor is not the cause. I only mentioned it initially so that people attempting to assist in the diagnosis would know what troubleshooting steps I had already performed.

[Gary_]

I noticed that you said you had removed the freeze sensor from the coils and let it hang down. I am certainly not an Air Conditioner Technician, but doesn't this impact the A/C negatively?? Just wondering!

[Antjaw]

1.) Is the thermostat in the line of cold air?
No, if it was, it would prematurely shut off, not stay running when the ambient temperature is colder than the thermostat is set at.
2.) Developing ice from the temp originally set too low.
No visible ice, and can see water running down the side coils. Thermostat on 80 and room is at 72 degrees. Regardless of ice, the unit should not be running if it is set at 80 and the ambient temp is 8 degrees below that.
3.) Thermostat mounted on the exterior wall.
It is mounted on the wall of the closet, 2 feet from any exterior wall. Test was performed at 8:00pm in the evening with no direct sunlight.

All measured temps were done with a Digital Thermometer resting on top of the thermostat.
All of the symptoms point at the thermostat itself. Tonight I will swap the thermostat in the front of the coach with the one in the back and see if that cures the problem. If that isn't the problem, I can only assume its a problem in the logic board.

[rgatijnet1]

Some thermostats, like in my coach, are mounted on the exterior wall. During the day, when the sun was shining on that wall, it was very inaccurate. At night, it was right on the money. I ended up taking the thermostat off and putting insulating foam behind it and spacing it an inch off of the wall. Now it works as designed.

[ksg5000]

When an AC unit coils develop too much ice from the temp originally set too low it tends to run constantly and the air produces isn't very cold. Turn off the AC for a half hour or so and let it "defrost" - then turn it back on and make sure you don't set the temp too low. If unit runs/cycles properly then you know you have solved problem.

[darsben]

Is the thermostat in the line of cold air?