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I hate OTR Air conditioning
After three attempts at repair, by two local shops and Dallas Prevost I still have a bus OTR ac unit that can best be described as piss poor. New fans, new dryer, two shots of freon, checking for freon leaks (none) and it still blows hot air.
No volume out the sides, now the damn compressor won’t even come on. Is there a breaker I am missing?
After two seasons in Texas with OTR basically inop and running a generator all the time to run the Cruisairs (which are pretty ineffective in 100 degree heat go down the road – tolerable but not cold) time is running out.
Any suggestions before I drive this POS off a cliff? 🙁
Mark
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9 Replies
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The only good news I can offer is Prevost stands behind their work and if they fixed it and now it has failed again they should put it in working order at their expense.
It could be as simple as a failed relay, or a system with a leak, but nobody knows the system as well as they do.
If you add a description of the coach, such as age, type and converter in some cases the answers can be more specific. Most members add it to their signature line.
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Mark: Do you know if the compressor is “OK”? We had a “kinda ok” OTR system on our coach from day one, would kinda cool, some of the time. Jeff Rowe worked on it a couple of times, in the end he determined that the compressor was shot and said it should be replaced, which we did. When he removed the compressor from the coach he pulled the heads and I think that three or four of the six cylinders had bad reed valves, so it “kinda worked”. New compressor made a WORLD of difference.
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Thanks for the info. Sorry for the rant earlier it tends to happen when one is up against a deadline to go on a 3 week trip and the coach is hotter than Hades. The coach is a 1999 Liberty H3 with OTR.
We have worked on it quite a bit and here are the problems.
The dash air blows cold (62 degrees) but the rear of the coach on the sides barely blows at all and what it blows is hot air. This seems strange beause I am under the impression they are the same lines – how could one end blow cold and the other hot? The coach temp rheostat in the front is full cold and I have the switch for the recirculation on. Is there a mixing valve/door somwhere between the driver and the rear that is stuck closed? Where would this valve be located? How can a compressor blow cold at one end and hot at the other? Plus why is there no volume of air coming out of the sides along the sidewalls? Is the fan bad? I am down to my last 2 days here and need to figure this out.
Thanks
Mark and Lorenda Wyant
Dallas, Texas
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I hope Jeff jumps in but from the brief description my initial reaction is the engine coolant heat exchanger at the whole coach evaporator is flowing hot coolant because either the control head or valve controlling coolant flow has failed. It sounds as though the system itself is working. Find the shut off valve on your coach that controls coolant flow to the OTR heat exhanger, shut it off manually and see if that fixes the issue until repairs to the control or modulating valve can be made.
I am not familiar with the H3, but on the XL the valve is a gate valve located on the driver’s side near the radiator.
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Thanks Jon but we already tried that. Any other suggestions would be appreciated. We DID find one fan bad on the evaporator and I am hoping they have one in stock at Prevost here in Dallas. Don’t know if that would cause it to be warm in the back though…
Mark
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Yes a single compressor, also a single condensing unit, however then you have two seperate systems, with two seperate evaporators, evaporator fans and their own expansion valves…So if you are not cooling in the coach side, if you have no flow of coolant that could be heating the system up, then we need to look at the fan and its speed, which I believe you have a seperate knob to adjust fan speed for the coach area on that vintage of coach….I would also check at the evap expansion valve that it is getting cold, verify each side of the dryer is the same temp also and it is not freezing up….That is some things to start looking into
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I completely forgot about the expansion valve and that may be the culprit. I think the fan on your coach is a double shaft motor with two fans so I’m not sure how one of the squirrel cage fans could not be working while the other one works. It is well worth insuring the fan on the evaporator is blowing.
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Those fans I have seen the set screw back out/strip on shaft and one spins while the other then barely rotates….Also is the fans coming on and running full speed or are they turned down…
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Mark: As Jeff pointed out, the key thing to remember is that there is one compressor, one condenser (the thing in an A/C system that gets hot), and two evaporators (the thing in an A/C system that gets cold). As a non-HVAC technician (hence a regular person), I’ve found its very, very important to understand its configuration when trouble shooting (and even running) the OTR system.
Mark wrote: “The dash air blows cold (62 degrees) but the rear of the coach on the sides barely blows at all and what it blows is hot air.” From that I would deduce that the compressor is working properly and “making cold”.
I think you probably have two problems.
Barely blows at all. Some air comes out, but not much? If so, then the fan is probably at least working. Is the “Coach Fan” control turned all the way up? I presume it is. Could it be loose in the dash and the entire device turning when you adjust it and you’re not turning it up at all? Play with it a little. See what happens.
What it blows is hot air. Again is the “Coach Temp” knob turned down to the coldest position? Is it loose in the dash? Can you see if hole device turns when you adjust it? As stated above, then it might be one or both of two things … expansion valve and/or engine coolant heat.
Since we have an XLV and not an H, I can’t go out to my coach and try to tell you where some of things are located.
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