Well I just rebuilt my friend's A/C tonight (1997 E320) due to a seized compressor. I had been planning this for about a week now and want to thank everybody on this forum for their EXCELLENT, EXCELLENT advice. All the info I gathered here made the job go very smoothly. I ended up replacing the condenser, compressor, and receiver/drier, and flushed everything else out with flush solvent and a compressor (except the evap and suction hose, due to difficulty removing and accessing).

The new compressor had oil in it, but I have no idea how much. I tilted it to get a feel for how much is in there; there was at least 2 ounces from my guesstimate. But I really have no idea how much. So I added a UV charge for good measure and hooked up the lines. I was able to put about 1 more ounce into a line going to the receiver/drier; there just wasn't much opportunity to pour more oil in, especially since the suction hose faced downward. So worst case scenario there may only be 3 ounces (?) of PAG in there (keep reading).

Once the system was sealed, I spun the compressor by hand about 6 or 7 times and then pulled a vacuum for about 1 hour (picked up a new economy 1.5 CFM vane pump at McCain's for $150). I spent a half hour refilling the radiator, hooking up the hoses, topping off the trans fluid, etc. and during that half hour the vacuum held with absolutely no drop. So I charged the high side with about 1/2 a can of R134A, and started to put the other into the low side. Then I fired up the car and set the A/C to max.

The compressor immediately kicked in, and I slowly coaxed the remainder of the can into the low side, and then over the next 10 minutes coaxed a second can into the system. At that point the pressures were 35 low, 250 high, ambient temp 90 degrees and vent temp 55 degrees. I know that's not quite where things need to be, but it seems like a good start. The car was still up on jack stands in my garage and not moving when these readings were taken.

Can anyone tell me if everything sounds normal so far? I was going to get a can of 4 oz. oil charge tomorrow and add that, since I have no idea how much oil is in the system. Is that a good idea?

I will say this - I shut the high and low sides off on the manifold, and then disconnected the yellow service hose just to release the pressure, and quite a bit of high-pressure refrigerant escaped from it for a couple of seconds. It was unmistakably bright green from the UV charge I put in it, but it was also VERY OILY. Does this mean I don't need to add any more oil?

I have read that adding too much oil can be worse than too little. Is there any truth to this?

LarryBible, what say you please?

Thanks!

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

I'm not sure how much oil goes in a 210 car, but I would definitely not put in another 4 oz. I doubt if it takes over 8 oz. total. Steve Brotherton pointed out one time that not enough oil wears out compressors but too much will destroy them.

The pressures will run different without ram air. You really need a pressure/temperature chart for that particular car.

I would recommend that you call Mark McCain at McCains and tell him what you did and ask his advice. He is always willing to help as long as you buy your parts and stuff from him. When I'm working on a car with which I am not familiar he will look up information and share his experience. He is what makes McCains the great shop that it is. He's a great guy.

Good luck,

Shoot, that's a tough one. You're likely down 2-3 ounces from changing the receiver and condenser. As well, some oil left with the old compressor. Some oil came with the new compressor. But too many unknowns to be certain.

The usual recommendation is to drain the oil out of the new compressor. Then add your own oil just before buttoning it up.

My guess - and it is just a guess - is that you are still a bit low on oil. Perhaps 2oz or so.

BTW, a 4oz oil charge contains 2oz oil and 2oz refrigerant.

I second Larry's recommendation of checking with Mark - he's a real expert, as opposed to we pretend experts.

BTW, where did you end up purchasing the compressor?

- JimY

Well I just started it up again while cleaning up the garage, and things seem to have stabilized a little bit, to the point where I am now getting 50 degrees from the vent at idle parked in the garage with about 90 degrees ambient temp (in the shade). I haven't checked the pressures again, will do that later today once I'm done cleaning up. I didn't think sitting overnight would drop the temp that many degrees!

I ended up getting the compressor from Foreign Car Parts in Dallas on Northwest Hwy and Plano Rd. Theirs was a rebuilt just like the dealer part, and carried the same warranty - 12 months. So I told my friend I didn't see any advantage in going with the dealer part, especially since we were doing the work ourselves (i.e. no labor warranty). I honestly would have had him buy the compressor through FastLane just to support this great site, but they did not have one listed. By the time the parts quote got to me, we had already committed to purchasing these parts locally.

I am going to add 2 more ounces with a small charge of R134A just for good measure. I'd call McCain's, as you suggest, but they're not open on weekends and my friend needs his car back this weekend.

Larry and Jcyuhn, you have both been a tremendous help. So have all the experts here! I'll let you know how the remainder of this job goes...

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Warranty on Mercedes parts is one year, parts and labor to replace it regardless of who did the install the first time around.

Len

Well I ended up talking to the guy at the parts counter at Foreign Car Parts. I inquired about the oil, and he got on the phone with the manufacturer to confirm that they put 2 ounces in the compressors when they ship (even though the box says it's dry). So between that and the 1 or 2 ounces I managed to sneak into the line, I figured there was about 4 ounces in there total. So I went to AutoZone and got one of those cans that had 2 ounces of PAG oil and 2 ounces of R134A refrigerant and added that. So I believe the system should have about 6 ounces in it now.

While idling, I kept adding refrigerant and the pressures didn't change much (28/225) until about midway into the fourth can, when the high side started to go up sharply. I decided to stop when the pressures were consistently about 45/275 at idle and 35/330 at about 3000 RPM. I took the car for a quick spin and noted the vent output was about 42 degrees when cruising about 50 mph, 95 degrees ambient air temp with about 50% humidity. Somehow I thought it would get colder than that, like maybe down to 35, but I guess not. 42 degrees sounds pretty bad on paper, but believe me it was plenty cold in the cabin. In any case, I wasn't going to add any more refrigerant so I finished up for the day and just gave the car a good wash. I'll throw the other 1/2 can in my buddy's truck. He may need a topup, but of course I will verify with the gauges.

Again, thanks to all here, and especially LarryBible and jcyuhn for all your excellent advice! Also many thanks to Steve Brotherton. We had a sharp exchange of words a few weeks back over a difference of opinion. But I still respect his knowledge and insight. I learned many invaluable things from his posts on this forum, and I don't think this repair would have gone so smoothly without them.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280