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Old 07-17-2018, 10:24 AM   #1
Baldicon
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Another AC Question

Brought home a new 3121RL a month ago, and have been camping in it since. One odd thing that I have noticed is that randomly, the AC fan will cut off for maybe 5 seconds and then start back up and will run for several seconds and repeat several times. I have watched my Progressive Industries amp meter and it shows the compressor still running. And, the compressor overload would not let it start back up with just being off a few seconds (pressures have to equalize). This is happening in both our bedroom AC and the living area heat pump. It usually does it after it has been running for a while. Doesn't do it all the time. No complaints about the trailer is staying cool, and there seems to be good air flow. Any one else experienced this? I know some have experienced restricted air flow issues, but I don't think that's the case here.
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Old 07-17-2018, 12:48 PM   #2
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M.O.C. #20477
Baldicon,

I tend to run my a/c on high fan vice auto to prevent this issue.
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Old 07-17-2018, 04:30 PM   #3
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Sounds like some sort of heat issue in the AC but yet the Tstat isn't satisfied yet and tries to keep it running
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Old 07-17-2018, 06:00 PM   #4
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The opposite could also be true. The feeze sensor could be in the wrong position (ours was on one) and sending a signal to shut down before it should.
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Old 07-17-2018, 06:27 PM   #5
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Would either the heat issue or cold issue shut just the fan down and leave the compressor running?
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Old 07-21-2018, 02:01 PM   #6
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Ours does exactly the same thing as yours Baldicon. Nowhere have I found a satisfactory explanation. I've just decided that it does not matter since the compressor is not cycling. Probably a thermostat thing.
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Old 07-21-2018, 02:08 PM   #7
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Ours does exactly the same thing as yours Baldicon. Nowhere have I found a satisfactory explanation. I've just decided that it does not matter since the compressor is not cycling. Probably a thermostat thing.
We've just had our trailer for month, and it's already getting to me. I can't stand not knowing what's going on. Also makes me wonder about the life of the motor. Sorry you're having the same problem. I'm suspecting something in the thermostat too. Someone mentioned a freeze switch, but I would think that would shut the compressor off and keep the fan running to melt the ice.
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Old 07-21-2018, 03:15 PM   #8
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Ours does the exact same thing. We really noticed it when we were in Catherine's Landing in Hot Springs 2 weeks ago. It was really hot that week unless the storms pop up.
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Old 07-21-2018, 03:58 PM   #9
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masterdrago and RoadRunnerTR21, do both units in your trailer cycle off/on? Both in mine do.
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Old 07-21-2018, 06:44 PM   #10
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masterdrago and RoadRunnerTR21, do both units in your trailer cycle off/on? Both in mine do.
Yes. I find that the bedroom is much more effected by this issue than the living room. I had originally thought it might be air from one of the ceiling registers blowing air on the stat. Found that was not the issue. It goes through spurts of doing it and I've not been able to pin down the pattern.

I did see someone way back mention that it might be warm air migrating up into the space behind the stats. They used foam behind stat to try a fix. I still don't know how to get the stat off the wall to check that. It seems like an easy experiment to try.
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Old 07-21-2018, 09:03 PM   #11
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Yes. I find that the bedroom is much more effected by this issue than the living room. I had originally thought it might be air from one of the ceiling registers blowing air on the stat. Found that was not the issue. It goes through spurts of doing it and I've not been able to pin down the pattern.

I did see someone way back mention that it might be warm air migrating up into the space behind the stats. They used foam behind stat to try a fix. I still don't know how to get the stat off the wall to check that. It seems like an easy experiment to try.
Same here, they both may run fine all day, and then just start acting up. I don't think warm air behind the thermostat would cause this since the compressor continues to run. But maybe the thermostat is smart enough to change fan speeds based on temperature while the compressor continues to run. But warm from the wall will make the thermostat not sense the room temperature like it should.
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Old 07-22-2018, 05:53 AM   #12
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Our A/C cycling happens more during the high heat in the afternoon and evening. One thing we did notice was that in the morning the rig was like a ice box. The AC would not stop running. DW determined that the problem was that the pantry, which shares a common wall with the thermostat, was very warm inside. When she opened the pantry door to let the warm air escape the AC stopped turning on.
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Old 07-22-2018, 09:07 AM   #13
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Originally Posted by RoadRunnerTR21 View Post
Ours does the exact same thing. We really noticed it when we were in Catherine's Landing in Hot Springs 2 weeks ago. It was really hot that week unless the storms pop up.
How did you like Catherine’s Landing?
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Old 07-22-2018, 10:30 AM   #14
Kyle and Lisa
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The digital dometic thermostats are very sensitive, not as pretty but we pulled the thermostat covers off and leave them off and have a lot less issues - temp., settings, and cycling.
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Old 07-22-2018, 11:56 AM   #15
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Another problem (but doesn't explain the fan cycling) is that the thermostat should be mounted as close to the return air registers as possible so it can sense the mixture of air returning from conditioned space. In houses they are usually mounted directly above the return grill if possible. The thermostat in our unit is on the opposite side of the LR from where the return registers are located, but there isn't a good place to locate it close to the return. You don't want to mount it on an exterior wall either. With our LR thermostat set to 79/80, a thermometer on the island reads 74/75. The bedroom operates a lot closer to the set temperature.
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Old 07-22-2018, 01:11 PM   #16
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Quote:
Originally Posted by Baldicon View Post
Brought home a new 3121RL a month ago, and have been camping in it since. One odd thing that I have noticed is that randomly, the AC fan will cut off for maybe 5 seconds and then start back up and will run for several seconds and repeat several times. I have watched my Progressive Industries amp meter and it shows the compressor still running. And, the compressor overload would not let it start back up with just being off a few seconds (pressures have to equalize). This is happening in both our bedroom AC and the living area heat pump. It usually does it after it has been running for a while. Doesn't do it all the time. No complaints about the trailer is staying cool, and there seems to be good air flow. Any one else experienced this? I know some have experienced restricted air flow issues, but I don't think that's the case here.
If you have the Fan in Auto what you are hearing is the fan Auto shifting from High to Low speed. Or low to high if you set fan to High and the cycling goes away then that is the problem! Not sure of the exact differential degrees but in auto if room temp is like 3-4 degrees higher then set point in Auto the fan will shift to High Speed you can just be in that sweet spot where it will be shifting like you are describing. to check if this is what is happing set fan on High or turn thermostat temp down a few degrees.
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Old 07-22-2018, 01:19 PM   #17
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If you have the Fan in Auto what you are hearing is the fan Auto shifting from High to Low speed. Or low to high if you set fan to High and the cycling goes away then that is the problem! Not sure of the exact differential degrees but in auto if room temp is like 3-4 degrees higher then set point in Auto the fan will shift to High Speed you can just be in that sweet spot where it will be shifting like you are describing. to check if this is what is happing set fan on High or turn thermostat temp down a few degrees.
So turn the fan to High and let it run continuously? It is set to Auto now. Sometimes in the off/on cycle, the fan speed does increase or decrease. Other times it stays the same. It sounds like I'm not the only one experiencing this.
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Old 07-22-2018, 01:27 PM   #18
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So turn the fan to High and let it run continuously? It is set to Auto now. Sometimes in the off/on cycle, the fan speed does increase or decrease. Other times it stays the same. It sounds like I'm not the only one experiencing this.
Correct set fan to high if I am correct you will not have the cycling.
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Old 07-25-2018, 02:18 PM   #19
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A/C cycling

Pretty normal if operating in auto fan. Bedroom unit if it’s the front one will cycle more because of cooling room area. I use high fan on both until just before ready for bed then switch to low fan. Just personal preference. Here’s what some don’t know about, remove the thermostats off the wall (2 screws) and you’ll find a huge hole where they pass a small wire through. Guess what the thermostat is really reacting to? The inside of an uninsulated wall! Use tape or insulation to cover/plug the hole allowing enough room for the wire. Will make a difference in how the system works. Good luck and happy camping.
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Old 07-25-2018, 03:55 PM   #20
Kent Carter
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Count me in! Mine does the same thing and the bedroom ac does it more often. Keystone c/s said it was normal.

This past weekend at about 2 in the am, the one in the bedroom came on for a few seconds and went off. It did this about four times before I had enough and shut it off.
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