A/C fan cycles

[Bagger]

I have an a/c problem with my 2018 Freedom Express. Randomly on startup, the compressor does not come on line till after the fan cycles on & off 5 or 6 times. Once the compressor starts, it cools down the camper fine. But the next time that the T-stat gets a call to turn on, it may start up fine or it might cycle the fan on for 1 minute, off for 1min 4 or 5 times and then the compressor comes. We have changed the t-stat, control broad, used different t-stat wire and finally the whole a/c. Still did not fix the problem. Not sure what to try next. Any suggestions???

[BriaBeck]

If you changed the whole A/C, and that didn't solve the problem, I'm wondering if you're seeing normal operation, but just not seeing what you expect. Sounds like you changed essentially the whole system, so having the same abnormal system operation in 2 completely separate systems is unlikely.



What kind of thermostats are you using? Could be that the deadband in your thermostat model is too "tight" and causing the rapid cycling.


There's a few guys around here that are good with A/C problems, I'm sure they'll chime in shortly!!

[Flybob]

What is the time between when it stops after cooling and when it tries to start up again. A/Cs have a time delay on the compressor that prevent it from starting too soon after stopping as the head( pressure) is too high to allow an easy startup.

[5picker]

Do you have a room temp sensor that looks something like this? (see below)

Some units must sample room air temp before kicking in the compressor.
It does so by running the fan for a short amount (several times) to blow air over the sensor for sampling.

[Thomas ho]

Leave it alone. LET IT CYCLE. Every time you restart it the computer chip starts over. Turn it on and go do you trailer set up projects.

[Bagger]

Here is a little more info on my problem; this could get a little wordy but I could really use the help. My sys is a factory installed Dometic Brisk 2.
I dropped my camper off to my dealership (3 hrs away from where I live) about a week ago, they trouble shot the sys, got with Dometic and decided to change the main unit under warranty; the t-stat & the control board had already been changed prior to this. I picked the camper up and spent the night at a nearby campground to test the system.
The a/c worked fine for about 7 hours, turning on & off maybe 10 times as it should while maintaining 75 degrees which was what the t-stat was set at. Then the cycling started again, just as it had before the unit was replaced. The sys was off for about twenty minutes, the fan came on for 1 minute, turned off for 1 minute. It did this on & off cycling about 5 times; then the compressor would come on and ran until the temp hit 75 and then turned off. Twenty or thirty minutes later, it did this same cycling of the fan on & off 4 or 5 times, then the compressor would come on and cooled the camper down. Then the system would run correctly ( fan on, 10 or 15 seconds later the compressor came on, cooled the camper down and turned off). It is a random issue; the sys may work correctly 5 or 20 times and then mess up for a couple of cycles and then work correctly again.
Background info; I had two mobile techs look at it, the dealer where I bought the camper plus I have 7 years of experience on residential air conditioners systems. The following is the sequence for what has been looked at or replaced. We had good voltage & amp’s (110 & 12 volts) at the unit when it comes on, replaced the t-stat, control board and then the a/c unit itself. It's not a dead band or delay issue and there is no remote sensor in the system. When it starts the cycle issue, the compressor just doesn't attempt to start (no LRA) until the fan cycles a few times.
This has all of us stumped. Dometic thinks a dirty power issue.