300SDL AC woes - PeachParts Mercedes-Benz Forum

Mike J · #1 03-07-2006, 07:25 AM

I'm not going to tackle the AC system myself. I'm comfortable with that fact, but wish to understand as much as possible what I'm getting into.
I thought I was making cooler warm air, but....
I took it to an indy I trust as much as any and he says:

No electric to compressor.
Not enough refrigerant for compressor to run. I read in an earlier thread that in some models when the refrigerant leaks out, it takes the compressor oil with it, and ruins the compressor. Is that the design in the '87 300SDL?

After converting refrigerant and charging up, and direct wiring the compressor, it still will not start, probably bad compressor.
He wants more time for diagnosis, but predicts compressor replacement, and who knows what in the controls, possibly the relay, or maybe the control panel.

Says compressor vendor will only offer 12 month warranty if he replaces dryer, expansion valve(I think), various and sundry et ceteras, and looking at about $1000 for this work.

Good news is he thinks I have a real strong 603.
I feel good that it has only used 1/8 quart of oil in over 1500 miles since oil change. No drips.

So I'm inclind to go the full boat on repairs. I have to have AC.
Assuming a $1300 bill, that puts me about $8000 into an '87 300SDL with absolutely no rust, very good interior, good transmission, and a strong engine....
Gee, and I could have had that 99 minivan with 90,000 miles and captains chairs.....LOL

R Leo · #2 03-07-2006, 07:42 AM

Join the club.

I've replaced the compressor, condenser expansion valve and drier in my SDL (I knew that I'd be changing all this out) but now I've discovered that the evaporator is leaking. Starting Wednesday, I'll be pulling the dash on mine so that I can replace the evaporator.

All this and I still don't know the status of the electrical controls for the system. I'm expecting the worst since the wiring to the compressor was totally hosed.

Some electrical woes can be traced to the "Klima" relay and I believe that there is a work-around for this. I haven't done any research so far; you might search the Forum for Klima info.

Quote:

when the refrigerant leaks out, it takes the compressor oil with it, and ruins the compressor. Is that the design in the '87 300SDL?

All systems will loose oil in the event of a refrigerant leak. The specific problem with the Nippondenso compressor used on the W126 is that it is intolerant of overheating. A failed condenser fan or pressure switch will cause the system to run excessive pressure on the high side, eventually overheating and destroying the compressor while simultaneously spewing a mixture of Teflon™ and aluminum shavings into the condenser. Not good.

Mike J · #3 03-07-2006, 07:59 AM

Thanks R Leo for the encouragement...

Well, you know the other day, when it was 80 degrees out, I had a puddle of water under the car, just like AC condensate dripping.

And at this point of time, I have almost no leaks hitting the ground. If the car sits for a couple of weeks, I get a spot of transmiission fluid about a quarter inch across.

dannym · #4 03-07-2006, 08:34 AM

As LEo said ANY leaking air conditioning system will leak oil. That's one of the easiest ways to check for leaks, just look for oil.

You said you "converted" your refrigerant. Does that mean you went to 134A?

I don't think you'll get away for less than $1,000 with a blown compressor. And your mechanic is right. You will not get a warranty unless you replace the dryer and probably the condenser too. Do a search on the internet for "black death" and you'll see why. Baszically when you lose the compresor the whole system is contaminated. Make sure your mechanic flushes everything that is not replaced.
Click here for Black Death

If you want to learn there is more than enough resources here and on the internet and at your local book store/library/automotive parts store.

DAnny

R Leo · #5 03-07-2006, 08:37 AM

Quote:

Originally Posted by Mike J

Thanks R Leo for the encouragement...

Well, you know the other day, when it was 80 degrees out, I had a puddle of water under the car, just like AC condensate dripping.

And at this point of time, I have almost no leaks hitting the ground. If the car sits for a couple of weeks, I get a spot of transmiission fluid about a quarter inch across.

FWIW, the condensate drain is on the left side of the tranny hump, just behind where your right heel would be with your foot on the throttle.

If that's all the leaks you have, you are either in grand shape or, there's no oil in the crankcase and no coolant in the radiator.

My SDL is most definitlely a love-hate relationship. I only had to give $650 for it, mainly because at the time it would only run about 40mph on level ground. I knew full well that it had been seriously abused (it's had a salvage title since the early '90s) and a lot of the systems didn't function but, her main purpose was to be a classroom for learning how to work on the 126 chassis and 603 engine. It has been that, and much more... BTW, the no power condition was the easiest fix so far.

That all said, I absolutely love to drive that car on the highway. And yes, it's a sickness...

R Leo · #6 03-07-2006, 08:39 AM

Quote:

Originally Posted by dannym

You said you "converted" your refrigerant. Does that mean you went to 134A?

No 'conversion' should be required since, AFIK, almost all '87 W126 cars came from the factory using R134a. Also, Mike J, if it actually is an R-12 car, you will be much better off keeping it an R-12 system because of cooling capacity issues.

TimFreeh · #7 03-07-2006, 08:46 AM

Quote:

Originally Posted by R Leo

No 'conversion' should be required since, AFIK, almost all '87 W126 cars came from the factory using R134a. Also, Mike J, if it actually is an R-12 car, you will be much better off keeping it an R-12 system because of cooling capacity issues.

Not true, MB did not start switching to R134a until around the 91-92 year timeframe.

bhatt · #8 03-07-2006, 08:49 AM

Are you sure on this? My '86 300SDL came with R12 (and still has it) and so have all the other 300SDLs I have seen.

I thought MB didn't start putting R12 in as a factory fill until the early 90's. Perhaps yours was converted?

I was under the impression *ALL* SDL's had R12 and should stay that way for best cooling performance (R12 is getting cheaper by the day now..)

Neal

R Leo · #9 03-07-2006, 09:01 AM

Quote:

Originally Posted by TimFreeh

Not true, MB did not start switching to R134a until around the 91-92 year timeframe.

I may be wrong since my information only comes from an aftermarket A/C parts supplier and my SDL has what look like stock 134a fittings and already had a 134a expansion valve in place.

However, I cannot imagine anyone going through the hell of replacing the txv on one of these cars just for a change to 134a.

One more thing, the replacement condenser I just purchased from FastLane has a 134a fitting on the high side...of course, if you have a standard schrader on the low side I guess that you could go ahead charge with 12 (provided that all the PAG oil was drained, the system flushed and proper lubricant put in it's place).

R Leo · #10 03-07-2006, 09:03 AM

Quote:

Originally Posted by bhatt

I was under the impression *ALL* SDL's had R12 and should stay that way for best cooling performance (R12 is getting cheaper by the day now..)

Neal

That's absolutely true for the 123 chassis' small condenser. The 126 has a pretty big condenser...

Mike J · #11 03-07-2006, 09:18 PM

My mechanic had to install the 134A fittings.
He said it was R12.
What can I say now?
Like I say, I trust him as much as any of the others I talked to.
And good comments on him from a couple of people I respect quite a bit.
And also from people I wouldn't know from Adam...

Yes, I thought to discuss the flushing process with him.

Thanks a lot for the discussion, fellers.

And, yes really, no leaks that amount to anything. Fuel lines starting to break down, sweating diesel, and a couple of small oozers, but nothing that drips or makes it to the ground, which is make or break for a home sales vehicle.
I really do like this car a lot. Got to get Sweet Thang to drive it for a bit and see if she doesn't want a 300d, 240d, 300cd, or whatever comes by. That will be spendy, because it will have to be a sweet car for my sweetie...

R Leo · #12 03-07-2006, 09:58 PM

Quote:

Originally Posted by Mike J

My mechanic had to install the 134A fittings.
He said it was R12.

Then he was right and I was wrong. Nuff said.

Mike J · #13 03-28-2006, 07:32 PM

...to the indy for the AC diagnosis and repair.
Prepped Sweet Thang that it could be a $1500 bill.
Got a call this morning that it was the AC controller, $225 for the part and total bill came to $618.00.
He said he ran it for an hour and a half and it maintained vacuum.
I'll pick it up tomorrow, and see if I can make cold air.
If I get good service out of it, that is a bill I can live with.