Different AC problem

[AVid]

Ran into a slight problem this weekend on my son-in-laws trailer. The AC works fine if you set the temp and run the fan on AUTO. The compressor starts and stops just fine. But....if you set the temp, run the fan on LO or HIGH, the compressor will run until the set temp is reached then shut off, leaving the fan run. However, the compressor will not start again.

I know what I know, and I also know what I don't know....and I don't know AC systems. My best guess is the thermostat is faulty. Anyone have any insight that may help us out?

Thanks!

John

[Iwritecode]

Originally Posted by AVid

Ran into a slight problem this weekend on my son-in-laws trailer. The AC works fine if you set the temp and run the fan on AUTO. The compressor starts and stops just fine. But....if you set the temp, run the fan on LO or HIGH, the compressor will run until the set temp is reached then shut off, leaving the fan run. However, the compressor will not start again.

I know what I know, and I also know what I don't know....and I don't know AC systems. My best guess is the thermostat is faulty. Anyone have any insight that may help us out?

Thanks!

John

I think that's how it's supposed to work. I was told during my PDI to always run the AC with the fan set to AUTO.

[Stormrider151]

We run our ac at night with the fan on low because we always sleep with a fan running for the white noise. The compressor turns on and off with the temperature. You may well have a bad thermostat. The trailer I have now came with the analog Coleman Mach thermostat and it is bad. It keeps trying to kick the furnace on without being told to do so. I'm replacing it with a Coleman digital thermostat. That should solve my problem and perhaps yours. You can use different thermostats like Honeywell in RV's. There are instructions on the internet as to how to do this. Some require small modifications to do it.

[Iwritecode]

https://www.youtube.com/watch?v=tYD5FN6SmjQ

[Ashley]

Originally Posted by AVid

Ran into a slight problem this weekend on my son-in-laws trailer. The AC works fine if you set the temp and run the fan on AUTO. The compressor starts and stops just fine. But....if you set the temp, run the fan on LO or HIGH, the compressor will run until the set temp is reached then shut off, leaving the fan run. However, the compressor will not start again.

I know what I know, and I also know what I don't know....and I don't know AC systems. My best guess is the thermostat is faulty. Anyone have any insight that may help us out?

Thanks!

John

I assume you have the Dometic Digital Thermostat as you didn't state what unit you have.

I had a very similar (But not identical) issue not long ago I will share with you in hopes it helps you.

In the Auto Fan Mode my compressor and fan would run like they should until the compressor cycled off one time, then the fan would kick up to high speed and the compressor would never run again no matter what. You could turn the whole system off with the thermostat On/Off Mode button, turn it back on and it would cool fine until the compressor cycled off again.

If you ran the air conditioning with the fan on High or Low speed, the compressor would cycle on and off as needed and the fan would continue to run as it should on the chosen speed continuously with no issues ever arising.

I first suspected the thermostat, but after researching and finding the thermostat is more of a control head and sensor that is merely sending signals to the control box I started second guessing my thoughts. Then, when it also appeared that you can either purchase the thermostat or a Thermostat/Control box kit, but not just the Control Box, I opted to purchase the kit knowing if I bought the thermostat alone and that did not fix the problem I would end up with an extra thermostat when I bought the kit. I figured one day I may need the Control Box even if it wasn't my issue now.

Ordered the kit ( Dometic 3313189.000 Single Zone LCD Thermostat and Control Kit Polar White Trailer Camper RV) for $75, the thermostat is $30-35 by itself.

I did install just the thermostat by itself first because I am one of those guys who has to know what fixed the issue, not just fix it and be happy. I want to understand it. It turns out I did have to replace the Control Box portion too. So now I have a back up thermostat anyway, but at least now I know more about how the system works and how to go about diagnosing any future issues.

One note, when you do replace the thermostat, control box or whatever, there is a "System Initialization" procedure that should be performed. It is in the instructions but can be easily overlooked. Ask me how I know.

I hope this helps you, if not maybe it will help someone else in the future.

[AVid]

My son-in-law does have the Dometic Digital Thermostat. I broke down and read the manual on the thing. The YouTube video guy is wrong.
I have the same thermostat in my fiver and it works exactly as described in the manual. I can set the fan on lo, and set the AC temp and walk away. The fan will run on low and the compressor will cycle on and off as needed. The furnace will not run.
If I set the fan to lo, and set the temp on the furnace, the AC fan will run along with the furnace fan.

Thanks Ashley for the link, I believe you have the answer. Gonna order the kit and try it out.

John

[Ashley]

Originally Posted by AVid

My son-in-law does have the Dometic Digital Thermostat. I broke down and read the manual on the thing. The YouTube video guy is wrong.
I have the same thermostat in my fiver and it works exactly as described in the manual. I can set the fan on lo, and set the AC temp and walk away. The fan will run on low and the compressor will cycle on and off as needed. The furnace will not run.
If I set the fan to lo, and set the temp on the furnace, the AC fan will run along with the furnace fan.

Thanks Ashley for the link, I believe you have the answer. Gonna order the kit and try it out.

John

You're Welcome and let us know the results. And I agree with you as to the functionality of how the controls work and that the YouTube video link posted appears to have incorrect info.

[bj983]

Mine doing samething used repair manual. http://www.cleggind.com/postal_tech/...376%5B1%5D.pdf
Found out thermostat bad using it. I had always use manual high fan run all the time ( compressor cycling on/ off ) but stopped working that way after year.

[lpforrest]

Mine is having similar problems the main air conditioner will trip the Breaker when outside Temp reaches 95 degrees and the one in Bedroom only runs on low speed and puts out very little air. When I talked to Dealer I was told second air conditioner will only run on low speed? Is this correct I do not think so.


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