When I bought the coach the dash AC was not working and was represented as "needing to be charged". So during the tire kicking phase I looked at the system and saw a standard automotive round swashplate style compressor and standard dryer and thought, how bad could it be. I shot a couple cans into the system and it started blowing cool, not cold so I figured it just needs to be charged, etc.. After pulling a vacuum and it holding for almost 7 hours I figured all would be well. Compressor has sight glasses for oil and that looked good (there was fluid in there). The door says 6lb 9oz freon - but.... this is a modified system with the compressor moved over by the 24v alternator, not a York 2-piston, etc... - basically Prevost won't touch it. However working on the AC compressor in this non-factory location is a dream compared to the stock location - see photos. I didn't get correct pressures until 8.5lbs and had better than cool air coming out of both units. Went up to just under 9lbs and with 53 deg air coming out I was happy. Then the next morning - no cold air, but everything running... Finally I called a friend with a repair shop who does this for a living and he told me to follow the pressure charts. Fine, I dumped another 6 pounds into the system until I got the high side to 250 and the low was at 60 (95 deg ambient). Running best it ever had until almost 1 hr in the compressor started making a noise that sounded like a Jake brake (if you can imagine that) and then high spiked and tripped the high pressure cut-off). Cycled a few times like that so I ordered a new compressor.
Finding one was interesting. Everyone sells it but nobody has it... I finally called Four Seasons as I'm presently in Dallas and they are in DFW. They had it on their website, I called them, they confirmed they offer them but I had to buy through a retailer. AutoZone of all places was one of their retailers. I gave them the Four Seasons number, they ordered it and 2 days later I had it. This was a Valeo VC31 compressor and now replaced by the TM31 is a huge compressor that takes 500ML of oil (vs the typical 150-180ML) and listed as "Bus" applications priced to the tune of $1100 and came with 24v clutch and the 2 x 1/2" groove pulley (several variations with 8-10 groove serpentine pulleys, etc.). Even the AutoZone guy commented OMG at the price - over 3 x the price of the typical automotive compressor. PAG-46 oil w/dye 8oz (243ML) $15/ea at the Zone)
The Prevost Ft Worth parts guy was awesome. He researched parts, brought out compressors, etc.. We found I have the modern dryer being used so I was able to buy from Prevost (granted it was $84 which is double the AutoZone price - I was ok paying the Prevost tax for the help I was receiving - those guys have been really good to us). Then there was the good `ole York 2-piston that went on almost everything with a Detroit Diesel it appears. Compressor was only $325 from Prevost so I looked at my mount and it would be an easy/quick conversion to the York set up and I could have the factory parts.... But... the clutch was sold separately for over $900. Well no longer worth the conversion to the reliable factory York. He did pull out a couple rotary style compressors they use on the new rigs which were a 7 and and 8 in sizes (I have a 31) and about the same thing you'd find on you Suburban. Both has mounting ears vs the threaded sockets like the York and my VC31.
Compressor arrived and I was thinking I'll get the 10% Military discount but.... no discounts on special orders...
So I flushed the lines with the AC Pro flush ($24/qt or $39/gal at AutoZone - used about 2 qts) and air. No metal came out, just oil and dye. So I installed the new compressor and dryer pulled a vacuum and after 2 hours of holding steady I started charging. Charged the to pressure on the high side 215-230 was the fluctuation on an 84deg ambient. The low side would fluctuate between 15 and 25psi - quite low according to the pressure charts but functionally this thing is blowing 43deg air at the vents. So my new capacity is actually 9lbs even - 12 cans (best price $10/can a WallyWorld). I'll monitor over the next week while we travel and take full advantage of the cold air, now from the dash vs the roof airs.
Point of all this - this was my first head scratcher with a weak ac compressor. There was double the troubleshooting steps along the items listed above for the entire duration. It's hard to replace something that is working, but just because it's working doesn't mean it's working well. I think this compressor had a valve stick or something - had that not happened it's hard to say that I would still not be fooling with a weak compressor. I've definitely learned something and melted enough miles in the sun room called the driver's seat to simply not mess around in the future in similar scenarios... All in ~$1700 w/free labor LOL.
Dash AC working again!
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