Automotive Air Conditioning Information Forum

Hello,

New guy here, looking for some help with my current a/c situation.

I have a 2002 Camaro with a 5.7 V8. My a/c system worked great since new having never been opened since new until I decided to do a cam and head swap last summer. In an effort to make working on it easier I had one of my techs evacuate the system so I could remove the receiver dryer and the liquid line. Before I thought about it my tech was done and he had not printed out the amount oil or refrigerant recovered nor had he payed attention. He said it wouldn't matter because it would not be much. While it was apart I found caps to close off the evaporator, suction hose and condenser. When I had the car running again I put the a/c back together again with a new receiver dryer, orifice tube and replaced all the seals I had disturbed. I told the same tech what I had replaced and he said no problem, he would add back a couple of additional ounces of oil when he evacuated and recharged the system. He did so and the system seemed to work fine from the driver seat for about a month.

The vent temp then gradually started to warm up. I had him recheck the system and the pressures were like 160 on the high side and 80 on the low side and when it recovered the system it was full. His conclusion was the compressor had failed. As it was fall and cooling off I decided to leave it empty and unplugged the compressor.

Fast forward to this spring I obtained a new Delphi compressor, receiver drier and orifice tube. I attempted to find the correct parts to perform a complete refrigerant flush of the a/c system but between my dealers GM Shop and 2 other local dealers I could not come up with a complete kit perform a "refrigerant flush". At this point I opted to flush it with a product sourced at the local auto parts store called Interdynamics CA1 a/c system flush. I used 2 cans, one for the liquid line and condenser and the other one for the evaporator core a/c hose assembly, what a mess! When I was done the flush was coming out clean and I used compressed air until there was no trace of moisture coming out of the lines and ports.

At this point I drained the new compressor and measured the oil by weight and it had 7.6 ounces in it. The system calls for 9.6 ounces. Following the instructions supplied with the compressor I put the oil back in the compressor and an additional 2 ounce(by weight) installed the new compressor and cranked it over by hand about 20 times. I took the car back to work and had them vacuum the system for a half hour per the instructions of the a/c flush to be sure the flush was removed from the system. Recharged the system to spec and it was blowing ice cold again.

Now again after about 2 months the vent temp starts climbing over a couple of days but occasionally will cool ok until I accelerate hard then the vent temp climbs immediately. Recheck the system and it is low on refrigerant. Evacuate and recharge to correct spec and the high side pressure is 165, low side is 82 and the shop temp is 95 degrees. Vacuumed it back down and inspected the orifice tube, it is clean. Put a new one in it and recharge to spec, same pressures. We do a sniffer check on the system and find the service valve on the high side port leaking.

Now I have another new Delphi compressor, a new gm receiver dryer, orifice tube, high side valve and an aftermarket a/c condenser. I have flushed the evaporator, liquid line and hose assembly with brake cleaner(This is what the a/c guy in our gm shop says he uses) and I am ready to put it back together.

Finally what it all boils down to, my questions:

I am concerned about what weight of oil I should be using. The original spec for the car is PAG 150. The compressor documentation says I should be using what the car calls for but there is a GM bulletin that says to use their universal PAG 96 oil. I am tempted to find some nice double end capped 150 pag oil as that is what the car was built with and I am looking to restore the system to its original reliability.

I am also concerned now about my means of flushing the system. I have given up on a liquid refrigerant flush as the dealers in my area don't have the means to do it and the tech at our own shop uses Brake Clean which is what I have used on the parts of my system I do not intend to replace. As there was no obvious metal in the system and all I trying to do is get the old oil out of the system. Is the use of brake clean better than using an a/c system flush that may leave a residue of an inferior type of oil?

Considering I have easy access add oil to the compressor, evaporator, condenser and receiver dryer and the system spec is 9.6 ounces how much should I add to each part of the system?

Is measuring by weight the same as measuring with a measuring cup?

If you have made it this far I applaud you and am grateful for your input. I thought I had a shop full of experts but I feel completely let down by them at this point.

Doug

Wow. Your A/C tech needs some training...

That is a V7 Compressor. So when you see a high side that is decent, and the low side is too high - the first place you look is at the Control Valve. 160 High x 80 low is a de-stroked compressor.

Now, from the sound of things, the first (likely OEM) compressor started having trouble after all of the work. Could have been some debris displaced during service, or just bad luck. Control valve orifices are small.

Round two. Fresh compressor. In an effort to do a great job, you settled for a flush nobody here would recommend. That stuff is a high flash point petroleum solvent - boiling point is over 140f. No way a vacuum will get it all out. One component of the stuff is D’Limonene. AKA orange solvent - it has a boiling point of 349 f. If you have ever used orange cleaner around the shop, you will notice it softens a lot of polymers.

It is possible the second control valve got contaminated with debris, or the O rings on it got damaged by residual solvents in the system. Sometimes residual solvents break down the refrigerant oil and cause mechanical failures in the compressor. hard to say what killed #2 without an autopsy.

To answer your question, refrigerant oil is measured like any other liquid, in a measuring cup. Put as much of the oil charge in the compressor as you can, just remember to spin it over after mounting. Put any extra oil in the accumulator.

if you have any of the failed compressors, have a look at them & see where the actual failure was.

.

With Variable stroke compressors- you put the oil in the drain bolt hole- on the belly of the compressor-- they have a crankcase that holds 3 ounces at any given time when running-- you can put the full amount in the crankcase, just that it will level out to 3 ounces as it runs..

Thank you for the insightful replies.

I agree 100% on the tech training issue. I have one in my shop who is a VW tech and we always flush with refrigerant when replacing a failed compressor followed by a new accumulator cartridge and expansion valve. He has a zero comeback ratio on a/c repair on a VW. The guy in my GM shop is apparently a parts changer. In any case I have worked on the independent and dealership side of the fence and have usually found a lot more knowledge and insight on the aftermarket side.

GM Tech, The instructions that came with the first compressor stated just that, Put the oil in the compressor. The instructions that came in the new compressor say to measure what came out of the old compressor and put back at least 3 ounces and some other specific amounts in drier, evaporator and condenser.

bohica2xo, I still have the Original compressor. Is there a chance it is still good or just good as a diagnostic tool?

The components that need to be flushed are the evaporator, hose assembly and liquid line. What would be the best way to flush/clean them so I can proceed with putting my baby back together again?

At this point I could easily replace the liquid line and a/c hose assemble but replacement of the evap core would be major surgery.

Again, I really appreciate your input.

Doug

One other thing...A/c Oil.

Gm universal which is 96 weight or some expensive 150 weight Pag oil?

Thanks,

Doug

Oh man flushing. Back in the day on this board there were some spirited discussions on the subject.

You mentioned Brake Cleaner before. That can be a useful tool for getting the oil out of some parts.

When considering solvents for flushing, I prefer the glass test. Use a clean piece of glass, laying flat. Put some of the solvent on it. Does it evaporate on it's own? Does it leave anything behind? If you run your finger over the glass after the solvent dries,is the glass still clean?

Cheap carb cleaner spray is mixed, recovered solvents. Usually leaves some oily stuff behind - silicones etc. Brake Parts Cleaners are usually safe for rubber parts (check the label) and virgin solvents.

The delivery method is as important as the chemical. You need a high enough volume & velocity to do the job well. The can nozzle is a bit small, so... Tap the can. Use a side can tap for refrigerant & a charging hose or beater manifold. Make any adapters you need from take-off hoses etc. Make sure any charging hose you use has no check valves in it.

Connect to the evaporator inlet, run a hose from the outlet to a safe collection point like a poly bucket Tap the can of Brake Clean at the bottom edge of the can. If you are just using a charge hose, this is it - the whole can goes through the evaporator in 15 seconds or less. Disconnect the can tap & connect your dry air - and blow the solvent on through the evaporator. An air fitting screwed in to a flare fitting works great for this.

For low pressure flushing with fast evaporating solvents, shop made adapters with OEM hoses or tubes & hose clamps are just fine. i have over the years made every possible Springlock adapter from old parts, flare fittings, clamps, epoxy etc.

I will not describe my refrigerant flushing setup here, it makes Karl's hair stand on end. Hecat commercial flushing equipment is the best choice for a busy shop.

Your V7 compressor may be fine. Best way to find out is to go through it. Here is a great how to from the old board

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Any chance you can get the VW guy to do your car?