I have an 07 6.7 cab and chassis that is used for a tow truck... the only added accessory to the engine compartment is a clutch driven hydraulic pump... here is my problem.... it keeps blowing ac compressors... we re do the entire system.... compressor, fluid line, accumulator, evaporator, dryer etc. have it vacuumed down recharge it and within 2 days to 30 days it blows the compressor again.... it has done this 8 times.... we have heard everything from the fan clutch is weak to the cycle switch in the line it self is bad, which we have also replaced 2 times... we don't know what to do....

the truck has 400000 miles on it and has recently started doing this within the last 6 months or so...

The compressors usually smoke out first then the bearing goes.... what gives?

 

First by "fluid line do you mean the fixed orifice tube? Second you say the compressor smokes then the bearing goes. Do you mean the clutch bearing or the bearings inside the compressor. Also are you getting the compressors new or are they a rebuild, if rebuilt I have seen bad batches of rebuilt compressors before. If you are not recharging yourself and the compressors are rebuilt they may not be adding any oil to the system. I would like to think whoever is doing the recharging is monitoring the pressures and would spot a very hi head pressure caused by a bad clutch fan. You say you have replaced the cycle sw, I would guess at the low pressure sw, if you have you may want to change the high pressure sw because if it's not a bad compressor or lack of oil then the high pressure sw is probably bad because it's supposed to open the circuit when the pressure gets too high for what ever reason. I would also inspect all the lines looking for a line that's been bent sharply or flatted reducing flow.
Does the truck have a winter front on it? With the aux hyd pump installation the belt is probably a different length, it's not too short is it and applying too much load on the compressor shaft?

 

Have you been adding the correct amount and type of oil to the system?

 

Are you adding the correct oil to the compressor and spinning it before the install? Another thing to clean is the radiator and condensor. They get loaded up with junk over time.

 

Most of the time we replace all the parts Comp. condensor, dryer, evaporater, and the orfice line... other times we have replaced the compressor and thourghly cleaned all other componets... it doesn't seem to matter... it usually starts with the clutch smoking along with a smell similar to burning brakes... then soon within a few days at most the bearing locks up in the compressor. We have added oil... vacuumed down the system and charged ourselves, had a local shop do it , and had the Dodge house do it and again... seems to make no differance.. So is there pressure switches in both lines? Also the guy at the shop that says maybe the fan clutch is out did make mention that when charging the high pressure got out of range and setting a fan in front of it seemed to bring it down to normal... but the clutch fans seems to be working normal - the truck never runs hot... it gets to about 205 degrees and fan kicks on and cools it down to 185, or so and then kicks off.... so I don't know, but oil has always been added to the compressor before installation... I really appreciate you guys input on this were stumpted...

 

If the high side is running high, you either have a partial blockage like a crimped line or kinked line or the fan is no good. But like I said if the high pressure is getting way too high then the high pressure sw should cut out the compressor, so you definitely have a bad high pressure sw but that is not your only problem. I believe the fan should electrically engage when the AC is on, (sorry I don't have a wiring schematic for your truck) if this is the case look for a pin pushed back in the connector. I would not let the truck go again without first curing the high pressure problem. One other thing, if the system becomes contaminated by the compressor seizing up then the system needs a flush but the accumulator and the fixed orifice tube need to be replaced every time.

 

Almost all of the compressors that I have had to install on my truck did not have oil in them, only a charge for testing.

I had to drain out the oil, measure it and then install the correct oil, same for every component in the system each having a specific amount of oil to add.

I run my AC without a cycling switch and as long as I have air moving across the coils I have had no problems.

It sounds like yours is seizing from lack of lubrication.

I had a suburban that would smoke the paint and then the belts off the compressors and found it was the fan clutch slipping, gave me head pressures of over 400 PSI.

Air conditioning is simple, there has got to be something being overlooked.

I bought a replacement line for my 1st Gen from Auto Zone, supposed to be a perfect match but when it was installed the hose would twist and crimp the hose, got 3 like this so I did not use them.

Compressor Oil Chart.

http://www.rtitech.com/downloads/New...Compressor.pdf

Jim

 

Does your hydraulic system have an oil cooler in front of the stock coolers? Sitting still while using the hoist/bed it could be dumping a lot of heat back into everything else. Do these have a viscous or electric fan clutch? If it's a viscous you may need to add a small fan behind the grill to aid air flow to the clutch while stopped.

 

Did you ever find the problem ? I have a friend that is having the same problem. Let me know what you found thanks .

 

New OEM compressor?
Used compressor?
Remanufactured compressor?