A/C Compressor

[David T]

In a refrigeration system the oil circulates around with the refrigerant. Each component holds some amount of oil. In a poorly designed or malfunctioning system the oil can get trapped in a part of it starving the compressor for oil. Or, in a system that is leaky, when any refrigerant leaks out it takes some oil too. Most shops will squirt more refrigerant in but few will ever add oil. Eventually you don't have any oil and the compressor fails. Flushing is an excellent idea to remove any contamination. You should replace the accumulator, you can't properly flush that. To do a proper flush you should flush each component separately. After a flush you must inject enough oil to compensate for the oil that will get trapped in each component. You also must vacuum the system into the micron range of at least 700 microns, 300 is even better. Good practice also means finding and fixing any leaks. To do this requires the right (expensive) equipment.

[Ron]

Today I took the compressor off the engine and drained it. I got an old man drip into the cup from it. Where the hell is all my oil??? I know for sure I filled it with the proper amount when I installed all my new parts. The oil that did drip out is a golden brown with no flakes. I'm going to order a flush kit, dryer and orifice. I have plenty of PAG oil for the replacement compressor.

Good choice.
If you are getting a SD7H15, use their SP-15 PAG oil.

Curious if you are certain about the proper charge before because you flushed the entire system and gave it a full oil charge (amount?), or ?

[dn010]

David, thank you for the blanket lesson.

Ron, I was able to purchase a good used stock compressor from Ethan. When I did all the AC work a few years ago, I did not flush anything out because everything was new minus my original compressor. If my memory is fine, I believe I added 8oz of the SP-15 oil to the compressor according to the Sanden manual, I don’t have the manual with me at work so I cannot confirm this until I get home. I added this oil to the compressor and the system was empty, dry and vacuumed down for an hour. The can of “SP-15” oil that I have is from Hervey from a loooong time ago, the label going around the can says it is Sanden oil but he put a small label “SP-15” on it so who knows what it really is.

I have had my car nearly two decades and overhauled the AC three times. Every time I had to work on this system, it was because of a broken evaporator connection trying to remove the accumulator. With my latest issue, I had no leaks, no visible oil drips or seepage from any connections and my air was super cold – only problem was the compressor making all sorts of noise! My other project car is waiting for me to shoot some urethane paint on it but I should have time this weekend to start disassembling the D’s AC system to see what went wrong.

Edit: It was 2016 when I replaced everything in my AC system, time flies...

[Ron]

Thanks!

Back when I did 1669, the Sanden instructions didn't mention vehicles with new systems and long hoses. And all of the relative D docs are totally screwed up. The Sanden Service Manual, V1, has a section titled "Oil Charge Determination for Long Hose Applications", but skipped CCOT. I got the new version which has it, but the formula is screwed up, e.g., it doesn't even work for the example given. I figured out what was wrong with it, but it's easier to use 1.0 oz per 10' of extra hose, found in another section. I guesstimated 20' and dumped 10 oz in it (which works out to be within 1/4 oz of what the formula gives). It was doing great when I sold it years later.

[dn010]

I have to order a new condenser/evaporator hose, so this project will be delayed a little bit. Current one had been too close to the steering joint, it is worn down pretty far.

[dn010]

Since my last post I had a chance to get some work done. I opened up the original compressor to look at the pistons, they had some minor scratching but I didn't come across anything broken or major damage but I didn't go further then checking the pistons. The compressor clutch was soaked with what looked like grease from the bearing and I don't know if it is epoxy on the coil but it is cracked, burned and blistering. The original compressor will remain out of the car and I will use the replacement. Last night I removed the accumulator thankfully without any issue which is a first for me. My biggest problem was the VOV was pushed way up in the evaporator, so I used some compressed air on the other pipe to build up pressure and then used a screwdriver to move the VOV back and forth until the air pressure pushed it far enough out that I could get it with pliers. The VOV looked good and not clogged. I flushed everything out with mineral spirits and there were noticeable particles in the flush that looked like aluminum so that is concerning to me. Most of the oil was in the evaporator but I can't really tell how much was in the system since it is all now mixed in the mineral spirits.

My next problem - I forgot my original condenser to evap hose has the high pressure switch and pressure relief valve built-in. After going over Dana's post, I realize I need the adapter 110527, so I will order that now and unfortunately more waiting before I can get all this over with. In the meantime, I think I will flush a few more times to make sure all of the particles have been removed.

[David T]

If you can get it, the proper flush is R-11. It comes in a small pressurized can with a hose. Any A/C supply will have it. Anything else could leave a residue. Since you saw metal, it is important to get a good flush.

[dn010]

I am going to flush it with mineral spirits again to see what comes out. The flakes came out when the evaporator was flushed but I'd really like to know where it originated from, my only guess is there is damage to the compressor that I didn't uncover since I didn't do a full tear-down. If there are still flakes then yes, I can get rx-11 and I even have a bottle of nitrogen to follow up with afterwards.

[David T]

I wouldn't get too worked up over some aluminum flakes. They could just be from original manufacture and never got cleaned out initially. I would flush till they no longer come out. The Nitrogen is for sweep charging and pressure testing. Once you finish flushing, you pressure test to 150-200 psi with the Nitrogen. Find and fix any leaks. Fill the compressor with oil if you didn't already, vacuum to 300 microns and charge with refrigerant. Do an operational test and you should be OK. If you want to, you can continue flushing with mineral spirits but I would finish up with the R-11 to flush out any remaining mineral spirits. Flush each component separately. That way you don't push any junk from one component into another. When you do an operational test I find it is good to put a fan in front of the radiator to get more air in like the car is moving.