AC cycling...Maybe??

Probably the fan automatically switching from high speed to low speed.
Mine does similar. I have the single unit Dometic digital thermostat. Can be set to hi, low, or automatic.

I had one that did the same thing. Control board was bad and compressor kept running

Automatic speed control on thermostat. Working as designed, only option is to raise or lower setting. We have this happen whenever the AC can hold or lower inside temp with fan on high, but now with fan in low speed. Drop temp settinf two or more degrees, fan will stay on high. Other option is to set fan to low speed, but will run all the time. Take your pick.

smkettner wrote:
Probably the fan automatically switching from high speed to low speed.
Mine does similar. I have the single unit Dometic digital thermostat. Can be set to hi, low, or automatic.

Yep, same here

Ranger Smith wrote:
I had one that did the same thing. Control board was bad and compressor kept running

The compressor will cut off. But DW gets paranoid that something is wrong and she'll turn it off, let it set then turn it back on. We just noticed it today, we were packing for our 10 day trip coming up.

There was another thread on this lately--same problem. Don't believe that this is right. Our Domestic runs on low, then cuts off with compressor running, then switches back on high fan for a minute, then everything turns off. I believe the bad board theory and will be checking this out.

I was thinking maybe the thermostat or at the unit may have been wired wrong. But for the most part it does OK.

Problem fixed and knowledge learned by replacing the entire control system (Digital thermostat, control box including the board inside, and the coil temperature sensor.) The digital thermostat now uses fewer control wires between it and the AC unit. Since it is now a control signal instead of a control wire, it takes 1 to 2 seconds for the thermostat to tell the AC to switch fan speeds from high to low or low to high. The 1 to 2 second pause during fan speed switches is normal. What is not normal, which my unit was doing, is to run on low for a long time, then switch the fan off with the compressor running, then switch to high, then switch everything off. The new control equipment solved that problem: it now runs on low, then switches the compressor off, then switches the fan off a bit later. The other problem that I had, was that it would not stay running continuously on low (the fan would turn off at the end of the next compressor cycle)—that problem is also fixed—the fan will run continuously on low.

Since the unit was out of warranty, rather than fighting with Dometic about whether they had a defective board and should replace it free, I just went to National Refrigeration, Shipshewana, IN. Their prices are so reasonable it was well worth the cost for a no hassle fix. Leon is the best at AC and refrigeration.

Additional note: the thermostat is designed so when in auto it only runs on high fan when the air temperature is 4 to 5 degrees from set point. I have seen conditions where it runs continuously at low fan while staying 3 degrees away from set point. And, the only solution seems to be to lower the set point or force it into continuous high fan. Can’t say that I agree with this design.

Actually problem not solved. Tstat now seems to need to be many, many, degrees from set point before kicking on. The only way that it seems to work reliably is to put it on continuous high fan with just the compressor cycling on and off. Junk design!