Roof AC problem

[Dick Osterhof]

Our motor home has two Duo-Therm Penguin model 630515 roof top air conditioner with heat pump & Comfort Control Center thermostat. Both units do the same thing. That is: in AC mode the fan comes on (I use the low setting), then the compressor starts and in a few minutes, about 2, the compressor kicks off and the fan goes into the high speed setting. In a short time the fan speed returns to low and in a couple of minutes or so the compressor restarts and the cycle repeats its self. After a few cycles they start to work just fine. I have written to Dometic asking if this is normal. Their response was to take to the shop! My question is; is this normal operation and if not is there a fix?

[RV Wizard]

Dick, the first question I have is the room temperature satisfied when the compressor cycles off? Some more info would also be helpful. What year, make and model coach do you have? Has any air cond. of furnace work been done on it? Have you tried resetting the T'stat?

[DonnaB]

Dick, you should take it to a shop. We have those same Duo-therm units and they come with a 3 year warranty. The fix may not be on your nickel if you hurry.

[Dick Osterhof]

Sorry that I did not give enough information. No, the room temperature is nowhere near being satisfied. The coach is a 2002 37 foot Allergo Bus which we purchased used in May of 2008 (motor home number 8 since 1972 and Allegro number 5!). It came with a complete history of all work and maintenance done on the coach. No furnace or AC work has been done. I removed the Comfort Control Center and replaced it with a CCC from another coach with the same system which did not have my problem. No fix! I reinstalled my CCC. And yes, I have reset the t'stat. I have checked and rechecked the wiring from one end to the other. By the way, I am a retired maintenance engineer from a large chemical company. My job is best described as "failure detective" 'Why did it fail and what can be done to prevent future failure?'

[Hyall]

Have you reset your Comfort Control thermostat?

If not remove cover pull fuse without touching anything - buttons, etc wait 5 minutes and reinstall again no pressure on any buttons let unit communicate 2 minute and set Temp see if that helps

[Dick Osterhof]

Thanks for the response Hyall. Resetting the CCC is one of the first things I tried.

[RV Wizard]

Dick, have you tried cleaning the data cable connections at the T'stat and the roof units? If this does not correct the problem, then you have one of two possibilities. Either the T'stat is going bad or the control board in the roof unit is.

[Dick Osterhof]

Thanks RV Wizard. I replaced the data cable connectors, cleaned the board connections, etc. Used a CCC from another MH that did not have my problem. Both roof units are doing the same thing so I have a hard time believing the roof unit boards could be bad. However, I will check the boards, just in case something may have fried them.

[Rex]

Dick, the only common thing to your type equipment is the thermostat, and the furnace. Now I don't see how the furnace could be causing this, but the set point for it to come on is controlled by the thermostat. If the cycling you are experiencing is when you are in Heat Pump mode, then it could be the furnace. In Air Conditioning mode, don't see how that would be.

Oh yes, there are two other common items. Those are the room temprature sensors. You should have one up front and one in the rear. Each should be connected to the air unit nearest to it. As there are two of they, they would both have to have the same fault to cause your problem.

[Dick Osterhof]

Hi, Rex! The system only acts up in the air conditioning mode. So far, it's a big mystery but it will eventually be solved. There are 2 temperature sensors, on in the CCC which is up front and one in the bedroom. I really don't care what the front AC does. When we are trying to sleep the switching from low fan to high fan really is quite annoying--keeps us awake. Both units do the same cycle thing, though.

[Dick Osterhof]

Took unit to authorized repair station and after two days and every thing checked and rechecked(did things that I had already done!) No fix and not a clue as to what is causing the problem! Typical results from an "authorized repair station". Which I why I don't like to take my unit to someone else to get it fixed. Tech could not even tell me if was or was not supposed to act as it does!