Sharing a successful repair of the dash A/C on a Class-A motorhome in hopes of helping another DIY'er.....................................
Its easy to see why so many folks give up when it comes to getting these systems working properly after your coach has a few years on it. Finding replacement parts can be a big challenge because some parts of the system are installed by the chassis manufacturer while others are put in by the coach builder. There’s also the challenge of finding information on the operational parameters of the system as not all A/C systems are designed the same, especially large volume bus type systems. In my case Evans-Tempcon designed the system on my coach & they are no longer in business. I stumbled upon their document set thanks to a fellow DIYer via Face Book and this ultimately gave me the information needed to get mine working properly. I had previously searched the web numerous times without success.
My successful repair journey:
I’m the 2nd owner of a 2011 SportsCoach 390-TS. The previous owner had the compressor, drier, & expansion valve replaced just prior to my purchase. It operated properly for several thousand miles but then developed a leak which I found to be in the evaporator. I purchased a replacement online & installed it but struggled to get the system operating properly. It kept freezing up which can often be the result of low freon. I added more freon to bring up the low & high pressures as indicated by online generic R134a charts but no go. It still froze up. I then discovered that I could manually cycle it on & off to keep it from freezing up. On for 10-minutes then off for about 5. Gave me something to think about during long drives, LOL, but it worked & kept me and the wife cool and comfortable. These thoughts led me to believe that I needed to replace the thermostat.
Upon returning home I began searching for a new thermostat and at about the same time found all of the manuals for my Evans-Tempcon system via Face Book. It included a troubleshooting guide which gave me exactly what I needed. The biggest discovery was the as-designed operating pressures. This system is designed to operate at much lower pressures than you will find on a typical auto A/C system. I also found the thermostat requirements which saved me about 50% on the price of the replacement part. After replacing the thermostat & removing some freon to bring the pressures in-range, it operated great.
Fast-forward to about a month ago. Outbound 800-mile trip & system ran fine the whole time. Camped for 10-days then moved down the road about 100-miles to visit some family for a few days. Turned on A/C after about an hour on the road but it wasn’t cooling. Stopped at the next rest area and discovered that the compressor was not even cycling. After the visit with family, we drove home over the next 2-days while running the generator & rooftop A/C. I’m totally disgusted at this point but don’t easily give up. Yes, I’m stubborn!
At home I threw the gages back on the system to discover that most of the freon had once again leaked out. Added two 12-oz cans with one of them containing leak detector dye so I could get system running again. Was pretty sure it was at the compressor because I could see oil on its backside but couldn’t tell which line was leaking. Once running and using a black light I discovered that it was leaking thru the bottom crimped hose fitting (beadlock).
My first thought was to replace the entire line but quickly changed my mind after crawling underneath the coach to look at the routing. That would be a nightmare and I would then need to get a custom hose built. After discussing it with my fellow DIY son-in-law, I decided to just replace the fitting and buy a crimper. After viewing some YouTube videos I ordered the crimper and started looking for fittings.
I knew that NAPA had supplied the replacement compressor so I started there and purchased what appeared to be the correct fitting based upon the ½-inch hose size. Guess again! It turned out to be a reducer fitting of which I struggled to find. I determined this by using my vernier calipers to measure the thread size (3/4-16) which cross references to a #8 nut. Already knew the hose size (#10) so went looking for the part. It turns out that automobile A/C fittings are normally not reduced. In other words, a #10 hose has a #10 nut on the other end. Of course, NAPA didn’t have one but I eventually landed on a fitting manufacturer’s web site which led me to several Bus parts suppliers. In the end the cheapest available option was an eBay supplier which sent me the part via USPS 1st class mail and no charge for shipping.
The hose fitting replacement took me about 2-weeks to gather up parts and tools but my cab A/C system is now back up and running perfectly again.
Moral of the story? Don’t give up too easily if you can repair stuff like this yourself. Just be patient & keep plugging away until you find what you need. I wound up only spending about $1200 between parts, tools, & freon. The most expensive part was the heater-evaporator coil assembly. Of course, I also spent many hours of research along with about 16-hours of my labor. I can’t imagine what these repairs would have cost me if I went to a repair shop. There was a point where I admitted defeat and just ran generator & rooftop A/C for a few trips. The radiant heat from the windshield we all love just kept cooking me up front so I went back to searching for solutions. Hope this helps someone else that is struggling with their dash a/c system!