[77newell]

My 93 coach has dash air conditioning that has not worked since I've owned it for the past two years. I'm obsessive about things that don't work, it just bugs me to have something there that doesn't do anything.

There is 65psi refrigerant in the system on the compressor outlet side without the compressor running so there is Freon in the system, though insufficient to make the system work. Its R12 Freon was banned starting in 1994 and replaced with R134a. the system can be converted but the cost remains unknowable until I tear into it following getting the R12 removed.

I recall hearing several comments that these systems are inherently unreliable, but I don't recall and can't find the reasons why this would be the case. If anyone has direct experience working on this system and can give insight into its weaknesses I would appreciate it.

I recognize the benefits of running the central airs and generator (exercising the gen). The cost of getting the system up and running plus its reliability will be the deciding factors in my decision.

[encantotom]

on my 90 i spent over a grand getting the dash air to work. it had previously been converted. i put a new compressor, dryer, etc.

even when it was blowing cold, it just wasnt very good. and then it would stop. after 2-3 times i just gave up. many others have had similar experiences. the dash air on that vintage was woefully undersized from my experience.

my series 60 coach blows many times better than the 90's did. it is much more reliable as well (though mine has a leak at a compressor fitting right now)

so....you just have to decide if the cost, time and result is worth it to you. could be yours works better than most of the others....

tom

[HoosierDaddy]

We just returned from a 5 day trip where it was sunny and in the high 80's. My 4 basement A/C's couldn't keep the salon area below 80 degrees. From mid-coach back it cooled very well. Once we hit the road the drivers area was very hot. I was contemplating trying to get the dash air working but the condenser on my coach is totally gone and I'm told they are unavailable. My next thought is adding an additional A/C /heat split system that runs off of the generator and piping it into the dash ductwork. I've even considered adding a roof air near the front.......The aluminum Levelor blinds seem to help but I am also looking for additional ideas to limit heat radiating in through the side windows.

[Richard]

Dean, something is not right with existing units. Three dometics in my 95 and you hang meat in 90 degree weather. Check the pressures

[lbrachfe]

3 Dometics and 2 are originals. Keep temp 20 to 25 degrees below outdoor temps. Use awnings and 95% UV shades to manage direct sun and make a/c more effective.

[folivier]

Jon, before you spend the money to convert to R134a why not try charging it with one of the hydrocarbon refrigerants? I believe they are much cheaper than any of the freon refrigerants. And I think I remember them actually working better?
If you have 65psi in your system then it may not be leaking?

[Richard]

The 65 psi is static. You can have just a wee bit of refrigerant in a system and it will show the vapor pressure of that gas at whatever the ambient temperature happens to be. You have to get low and hi side readings with the compressor running and both fans running on the condenser and evaporator to tell if the unit has enough refrigerant to cool.

[77newell]

Yea, Richard that makes sense. It really wouldn't take a lot of liquid for it to maintain that pressure, a tiny amount. The only relevance of that number is that the system is holding some pressure so it is not completely open to the air, as in having a hole somewhere. It gives me some hope, probably false, that the system can be made to work since it won't be full of corrosion.

Tom: when your 90 A/C would quit working, what was it that failed. And since your "new" coach's air seems to work quite well, how does the construction of that system differ from the 90 coach. Any insight you can provide might help me understand the likelihood that I can make my 93 system work. Of course I'll end up with a dilemma; am I willing to risk resenting chucking money down a rathole more than it niggles me that something that should be working isn't working. Ahhhh, the choice we face.

[77newell]

Having crawled around the system for awhile here is what I think I found. The fittings on the system are consistent with R-12. Starting at the compressor the system seems to be configured as a hybrid: compressor - condenser coil with electric fans - accumulator/drier - orifice - evaporator. I can find no pressure switches connected to the system so unless there is a timer somewhere when the A/C is turned on the compressor runs continuously. With the A/C turned on the compressor clutch does not engage, I need to follow the electrical to determine why.

In regards to refrigerant there are options. Each of us gets to choose what risks and benefits make sense.

1) Stick with R-12 and risk damaging the ozone layer with expected leaks. Ozone layer destruction is the justification for all the restrictions on R-12. This system has a large number of mechanical threaded connections plus a rotating compressor shaft that can leak.

2) Fill the system with propane/isobutane. This is illegal according to EPA with the rationale that it is flammable and could cause considerable burning in an accident. It cools better and runs at a lower pressure than R-12, better efficiency. Our systems would require about 4lbs of the stuff. This refrigerant has essentially zero impact on global warming if leaked to the atmosphere.

3)Convert the system to R-134a, the currently used automotive refrigerant. The system will lose some cooling and will run at a slightly higher pressure, though not enough so to create big problems for the installed equipment. There is some debate about whether the hoses need changing with the latest consensus that if the hoses have been run with R-12 for some time they will be coated with enough oil to prevent the migration of the smaller R-134a molecules through the hose. If you have a hose leak then you would have to install hoses designed for R-134a, they have a nylon liner that is impervious to the new stuff. R-134a will contribute to global warming in a small way if leaked to the atmosphere and while not inflammable it can smolder a bit if released. Work is underway to eliminate the use of R-134a in vehicle systems.

4) Convert the system to HFC-152a. This material is commonly used in dust blower cans to clean your keyboard and other electronics. It has a far lower global warming impact than R-134a. However it is somewhat more flammable than R-134a and autos being designed to use it will have vent valves releasing to wheel wells in case of an accident. The fire risk is not great, but not nonexistent. It will cool better and run at slightly lower pressure. The existing hoses are just fine since the molecules are larger than R-12. There are can taps that squeeze onto the side of dust blower cans to allow the filling of the system. EPA has not approved the use of HFC-152a for vehicles.

I'm providing this review for information purposes only. I'm not recommending any approach, each owner needs to decide what tradeoffs make sense, and there are tradeoffs to every approach. I will say that if I were to use any approach other than R-12 or R-134a I would evacuate the refrigerant prior to selling the coach to minimize my liability.

From what I can tell thus far, the dash air capacity is about equivalent to one house air conditioner.

If you are aware that something I've said here is in error please let me know and I'll post a corrective post.

[Mxfarm]

Chuckle, chuckle....

#2 - surely they're not thinking that's of grave concern as flammable substance on the highways these days. BTW, I have many miles behind the wheel of a propane powered vehicle.

marc