1997 Marathon/Cruise Air ?

Hi.
We are really enjoying the 1997 Marathon XLV that I purchased in February. However, I am having a recurring problem with the Cruise A/C's. Three units on this coach, which is barely adaquate in the southwest. The rear unit regularly shuts down and flashes the "HI PS" code which means too high pressure. I have also had the front unit do the same. I have had it into Desert West Coach twice for them to check it out. They found the freon charge to high the first time and nothing the second time. Still I have the same problem. The filters and coils are all clean and the condensate drain pans are working and clean. Are these units just tempermental and overworked?
Thanks,
Jim
775-843-8656

Jim, these cruisairs are very nice units, they need little maintance. You are having only the problems that the service person fixed or tryed to fix. If he has over filled them then you are suffering the mistake.

I think at this point, it might be wise to have them vaccumed and refilled to the proper levels. Have them checked for a vaccume hold and then refill.

We can sit in 100 plus degrees and use only 2 of the three and have them set at 2/3rds of the max. setting.

Not running down the road though, thats a different story. Have to run the dash air.

Jim, if you are trying to use the units right immediately after pulling into a hot asphalt or cement parking pad, the thing to do is hose down the pad under the bus where your units draw air from underneath. If the parking area is too hot, you will be drawing hot air up into your unit which will give you that high pressure signal.

Jim
I came back from Las Vegas at the end of June and fried down their. I also have 3 CruisAir units. I got HI PS reading also and while I was having the unit checked out I was told that the compressor discharge air was too close the intake duct. This cause the unit to get hot and hotter increasing the pressure. So I created a housing to devert the air intake and discharge away from each other. I will not be going back to LV to test it. The other thing to check is if the compressor fan is running if it doesn't the unit gets hot again and you get a HI PS reading and shutdown.
GregM

Jim,

We have discussed this scenario often on this site and the Prevost-Stuff site.

Your experience should be noted by everybody seeking a coach. Cruise Airs are excellent for providing heat and cooling to a parked coach. They are less ideal as the AC source for a coach that is in motion, and in the case of a 45, three are inadequate when dealing with high temperatures.

Your condensing units are pulling in cooling air that is extremely hot. The highway or road is absorbing heat from the sun and radiating it back up. You are finding that does not provide sufficient cooling for the condensing unit and your AC shuts down.

If a coach does not have OTR, it should have roof airs where the air passing over the condensing unit is ambient and is not heated air radiating up from the highway.

Going further, if the coach is a 40, three typical roof air or Cruise Airs will likely be adequate, but a 45 needs a forth unit or the coach needs to stay out of the hot temperatures.

Others will disagree, but these coaches all need OTR air to keep us comfortable in all conditions. It is dumb to pay what we do for them, and then find out a guy in a Winnebago is a lot more comfortable than we are.

Jim,

My 97 Marathon has 3 cruiseairs and they worked great, both sitting still and on the road. Jon has a good point on the number of A/C's, mine was a 40, but a 45 is a lot to cool with only 3. I never experienced any heat related issues with the intake, but was never anywhere exceeding 100 degrees either. If you get them running and solve your head pressure issues, you can adjust the SMX controls to increase the fan speed that may help inside.

I wish we could get someone from the Cruise Air company along with a roof air manufacturer to weigh in on this issue.

I had similar issues with Cruise airs as Jim on a 95 degree day between Jamestown NY and Knoxville. The bus system tripped a breaker and would not run so I attempted to run the Cruise Airs. They ended up cycling on the over temp switch in the condensing units and for all practical purposes ceased functioning. Yet when the bus was stopped, and providing shade to the ground beneath it, the Cruise Airs worked perfectly.

The roof air systems have a reverse problem that has likely been addressed in the engineering of the units. The heat radiating from the roof of the RV when stopped should have the same impact as when Cruise Airs are picking up heated air from the road. They may have a larger condenser coil or the air flow may be better.

In Tom's case it may be that in his Marathon the air intake and exhaust may be more efficient than on my Liberty. Without expert input we can only speculate.

My cruise airs (3) work good, but I suspect they could use a recharge & service.

I don't have OTR air, and was advised before I bought one, not to get it, as it soaked up a whole bay, was prone to breakdown, and very expensive to fix.
That opinion came from a very experienced bus person (in the industry) who had no pecuniary interest in not telling the truth. His further instruction was to make sure to buy a series 60, and make sure to get a 6 spd ally. (for what thats worth).

I am sure there are people who have had good and bad luck with any system, but just throwing that out there.

Mine also has a secondary engine driven compressor that essentially drives two more "dash airs", one in the galley and one in the bedroom, so it basically has three zones of cruise, and three zones of engine driven air.

You almost need a systems engineer to navigate these things, but its sure fun :)

I am hoping to visit my bus in Havasu this weekend, so it should be a bone chilling 120 or so there!, but need to fire everything up and move it around and keep everything limbered up.. Try to do it monthly or so.

Dale/Gary/Greg/Jon/Tom,
Thanks for the info.
I'm picking the bus up in the morning, and will also call Marathon and pick their brains.
It is likely the charges aren't exactly right.
However, DWC says you almost need to set them when the outside temp is 110F+ to get them correct for operations in the desert.
Different line set lengths etc.
Heading off to Oregon in a week.
Maybe it will be better going north.
I've been told that when I get the Hi PS shut down, to turn the unit off wait 10 minutes and start it up again?
Jim

Forgot to add to keep the interior fans on high as not to freeze up the condenser. Good Luck!

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

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.