1997 Marathon/Cruise Air ?

[Ray Davis]

I had the same issue with my CruiseAirs when I first purchased the bus. Driving back from SLC Utah to Las Vegas in 120 degree heat, and all the CruiseAirs shut down.

They really do not like running in extreme hot temperature when driving. Once parked, and temps cooled down they were fine.

I am now able to keep the coach pretty darn cool with the Country Coach air, and only need to add CruiseAir occassionally. IF I did run CruiseAirs during the summer in the desert, I would try cycling them, maybe 30 minutes apiece, keeping one off, two one, letting one cool down?


ray

[Jon Wehrenberg]

It is not really an issue of "cooling down". The condenser coil is a radiator that is required to pull the heat from the refrigerant. The refrigerant draws heat from the coach via the evaporator coil which as the name implies evaporates the liquid refrigerant thus drawing heat from the adjoining air to accomplish that. That air comes from the blower drawing the coach interior air across the coils.

Since refrigeration is a closed loop cycle, that heat that was absorbed by the refrigerant is now in the condensing coil and as that name implies the heat in the gas is now discharged to the atmosphere so the gas can condense into a liquid which ends up back in the area of the evaporator. (I am oversimplifying here a lot).

The heat that must be removed in the condensing coil is absorbed by the air passing over the coils. If that air which comes from outside the coach is excessively hot, and the difference in temperature between that hot gas and the cooling air is negligable, then condensation does not take place. Then the system stops functioning.

The solution is varied. Use cooler air, Spray a water mist so the water absorbs the heat to evaporate thus increasing the efficiency of the coils, or expand the size of the condensing coils so it will cool the hot refrigerant gas despite a relatively small temperature differential.

Unfortunately none of the obvious solutions are practical. Shutting the AC down for a short time allows the slight cooling of the refrigerant and the system will again function for a short time, but not for a long enough time to cool the coach.

One of the solutions is to not expect something to work when it was not intended originally to work as it is being used. A roof air owner never complains about the units stopping while going down the road. I suspect in similar temperatures, while a coach with roof air units is parked and the heat is radiating off the roof, it is possible the roof air unit will be struggling to work. OTR guys. That's the answer.

The big guy did it right because he has one of the rare Marathons that was actually designed to stay cool in the desert southwest. He has OTR.