As per an earlier post, dash air was not working, compressor was short cycling and no cold air. Since this post, I purchased a good set of AC gauges to accurately diagnose my problem. The gauge I had (low side only – cheap setup from Auto Zone) indicated almost a vacuum during compressor short cycle, so I assumed a blocked expansion valve as others have experienced. I also lost even this short cycle. When I installed the gauges and hot-wired the compressor readings were normal and system worked fine.
While observing pressures, there was a puff of smoke and I lost the clutch (clutch field coil burned out). Foretravel said they had a clutch kit for $287.00. Started calling around and finally found a kit at Yellow Rose (FW Texas) for $60.00. The original pulley diameter was just under 5 inches, but could not find one anywhere. Replacement 5.5 inches.
With the help of forum members, I located the clutch relay in the engine compartment on a relay board. Upon inspection, I found all components on the board corroded and festered. I replaced 4-15 amp breakers, 2 bosch relays and their plugs, and cleaned all connections or replaced. Every one of these circuit breakers broke apart when I attempted to remove the nuts from the terminals. This was a difficult repair in that our coach has an e-w bed slide and a removable hatch to gain access, and space is very limited. These components located behind hot engine and subject to water from the road is a bad design (should be in a dry box) I used waterproof terminals and connectors and after testing packed relay plugs, and smeared all expose circuit breaker lugs with silicone die-electric grease. Hope it lasts many years. Thanks to all who helped me with this problem. – dash air is 48 degrees.
Gregory S
2003 Designer
There were 2 components on this board and I would like to know their function. One was a heavy 75 amp Bosch relay, and the other was some kind of heavy potted block below the relay.
If you can, take some pics. If we can't figure it out, James Triana or someone like Keith at MOT can. With all the extra room on these coaches it amazes me they don't properly weather protect electrical components. Plastic junction boxes are easily sourced in many sizes.
I'm glad you are taking such good care of this coach... Keep me in mind when you decide you need something newer in a few years! ;D
I have jusy replaced those same relays and 15amp circuit breakers and mine too were all rotted out. To protect in the future I have draped a plastic cover over the whole panel and put a "curtain wire" strap across to hold it down. I will soon find out if the heat has any effect and will r+r if necessary. I still have not got my air working and I do know the refrigerant has gone (so must be a leak somewhere). Jumping the low pressure valve has not made the clutch engage but I put 12v to it and it works so I am hoping that either the Binary switch or just a recharge will make it work. James told me it takes 5-5 1/2 lbs. Any other ideas on this clutch or??
John
Depending on if it is the larger one underneath (90 AMP CIRCUIT BREAKER) or the smaller one to the right underneath it is a (30 AMP CIRCUIT BREAKER) on ours.
A few weeks ago I found I had a frozen AC clutch bearing and after replacing the bearing and repairing the worn compressor end plate with shims and JB weld, found that the clutch was cycling off and on. It was putting out some cool air. Added three 12 oz cans of 134a, cooling increased, but both high and low pressure sides were low; 5-10 psi on the low side and 150 on the high side. Led me to believe that the TXV valve was clogged. After a conversation with a compressor rebuilder, I decided to add some more 134a before replacing the TXV. Today found a few bubbles in the sight gage, added 4 more cans and the high side slowly came up to 230 and the low side increased to 10 - 12 lbs. The low side is still lower than my cars, I think it should be up around 20 -30 psi. But it's high enough that the compressor does not cycle off and on. That occurs at 5 psi on the low side. Peter reported that his 34' coach takes 5.25 lbs of refrigerant and a 36' coach should take more. I have put in 6.75 lbs and will leave it that way and see how long it lasts. The last time I added 134a was in 2008. If it doesn't have a leak, I suspect that the TXV may have a clog, although cooling is fairly good. I didn't have any condensation on the suction line at the compressor. Engine speed was 1000 during this process. A trip is planned last week Jul into Aug, will see what happens.
I think I put in about 8 cans of R134a about a year ago. I could see some evidence of leakage near the front seal in the compressor. A year later the system is still cooling well.
I probably put in too much R134a. I was trying to get the low side up to somewhere above the 32F boiling point of R134a according to the gauges. The high side was approaching 300 psi in 95F ambient temperatures, so I finally quit. The results have been good, and fortunately I think I didn't damage anything.
Our coach is 36'. It takes a lot of R134a to fill liquid from the rear to the front of the coach. A longer coach will take even more.
Rough guide to adding R134a to a system.
Assuming you have a sight gauge, I add refrigerant til bubbles in sight gauge almost quit and then I quit.
My system has a leak and I know where it is BUT to fix I will have to blow down system, replace a schrader fitting, evacuate and then recharge. Since I have Been getting by with a few ounces of R134a for about 4 years I think I will let it be. Not very scientific but it works.
Another TIP, On my GV there is an air inlet on the plenum behind the removable hatch in front, this inlet allows outside air in to temper the system in both heat and ac mode. I closed this off with aluminum and aluminum tape and system seems to work much better.
As far as pressures go, your coach will most likely run somewhat lower pressures than your car, due to the relatively large condenser and evaporator. I would charge until you have cold air and no comp short cycling. the lower pressure you can get by with the easier it is on componets, and those long hoses that would be a bear to replace.
We have an appointment at a Cummins Service Center on Tuesday for a non cooling dash ac unit. Sure would be helpful to be able to point them toward the relay / circuit breaker box instead of having to search for it. The system has several new componets installed by the factory a year ago. Seems as though the compressor does not cut in when the unit is turned on. We have a 1998 U295 36 foot.
Thanks to all, Bill
I have a 2000 U295 36 and my Relays and 15amp fuse (circuit) breakers are under the bed in the engine compartment on the left of all the wiring above transmission ( best I could explain). There are 3 little metal boxes (about 3/4" by 1 1/2") together and the right hand one on my unit is for the cooling fan, the middle one for compressor and the outside one is for the remote start 30amp. The other 2 are 15 amp. They were rusted out inside so replaced and I replaced the relays ( but I do not think they were bad) If your refridgerant presure has gone then the system will not work regardless. They will check for that and also if the clutch works by jumpimg 12v to it. There is also the low pressure switch to check and the Binary switch on drier. It will most probably be a Low pressure problem.
John
Many thanks John. Will give the info to the service rep as know these guys work on Cummins equipment but am sure each manufacturer installs where they choose.
Bill