How to flush A/C compressor

If there is debris in the compressor, you are past the point of trying to save it. The damage has already been done. I have a friend going through this right now with an 2007 truck. I helped him rebuild it six years ago after being hit so hard in the front, it pushed the engine through the firewall. He put on a new compressor and charged the system. Worked fine for four years, then the compressor clutch went out. Another new compressor. This one lasted two years. New compressor again along with a new accumulator and hose with the orifice tube. Worked fine for well over five minutes, then locked up. Replaced under warranty. That one lasted thirty minutes, then locked up.

Finally did an autopsy and found powder and chunks inside. The "wobble plate" had been torn apart causing the powder. After consulting a third expert, it has been learned that most newer condensers can not be flushed effectively. The chunks in it will not usually make it back around to ruin the compressor, but any blockage it forms will severely limit the flow and the cooling efficiency. At this point an entire kit is on order including condenser, compressor, evaporator, accumulator, and all hoses. This is going to be a really major repair.

Why do you think there is debris in the system? Was your old compressor locked up?

First lets clear up the clutch issue. If it seizes, it will cause the compressor to run continuously, that's all. If the compressor seizes, or locks up, the clutch will be forced to slip and eventually be destroyed, or the belt will slip, which is less likely to occur. The compressor can lock up from something breaking inside it, but more often from a piece of debris that circulated around and got into it through the low-side hose.

If you saw white smoke, look for a receiver / drier with a spring-loaded relief valve on the side. If high-side pressure got too high, that valve would have vented most of the refrigerant, and that would cause a loss of cooling. Try spinning the compressor by hand. If it turns freely, I doubt debris is a concern. Instead, I'd be looking for a condenser with blocked or restricted air flow, or something else that would cause the high side pressure to go too high. Be sure the condenser fan is working.

Dandy. So debris is not the concern. It sounds like it just may be low on refrigerant. One thing a lot of people are not aware of is the valves used for checking pressures and charging the system always leak. Their sole purpose is to hold the refrigerant in between removing the hose and installing the cap. It's the cap that does the actual sealing. Check if either of them were left off at the last service.

You should also be able to check for low charge yourself on an '01 model. On all of my Caravans I have to loosen the jack, then there is a sight glass on top of the receiver-drier. Your model is newer than mine and your jack is not in the same place, but I think you'll still have that sight glass. With the AC system running, you should not see any vapor bubbles in that glass. If you do, it's low on charge. That will cause the cooling to occur in the hose under the hood, and not in the dash where it's needed.

Don't believe everything in the service manual. 68 degrees is REAL good if the outside temperature is over 90 degrees. The system is only supposed to lower air temperature by about 20 degrees. The comfort comes from condensing out the humidity. You also have to remember the evaporator can't be allowed to go below about 40 degrees. If it gets to 32 degrees, the condensed water will freeze into a block of ice that stops air flow. Refrigerant has a useful characteristic where its pressure closely equals its temperature. The 25 psi in the manual is the point at which the low-pressure cut-out switch or pressure sensor, says it's time to stop the compressor because pressure and temperature are going too low. The 39 psi is closer to what they want to regulate at. Then, with the evaporator temperature near 40 degrees, consider the HUGE volume of 100 degree air you're blowing through that little set of cooling fins. It's hard to imagine how the air temperature can be lowered by 20 degrees.

You'll also find the temperature at the ducts will drop a little more when the fan speed is lowered. Lower air volume means less heat to remove from it, so the evaporator can do an even more effective job.

I don't recall ever seeing a high side up over 300 psi. That would suggest there's a restriction. There have been plenty of H-valve failures, so that would be my first suspect, but you'd have no cooling then. Look at the receiver - drier to see if it's cold or frost is forming on it. That would indicate it is restricted. Being new, that isn't likely either.