1999valkyrie

'93 300e, 2.8, 118,000 miles. Everything seemed to work OK with heat all Winter but it's not blowing cold when the A/C is on. The dealer wants something like $250 for a "flush & re-fill"...yikes! Goodyear service want's $54 for a performance test (leak check, compressor function check etc.). I think it's $5/lb for R134a re-charge.

1st question, how likely is it that a re-charge will correct the problem? I guess the real question here is...should I brace myself for a big expense if it's the compressor? And, how common is compressor failure?

2nd question, if it's not the compressor or the need for a re-charge, what else would cause the problem?

3rd question, is there anything about a Mercedes A/C system that's unique such that a Goodyear Center couldn't diagnose & correct?

Your feedback/advice/help would be appreciated.

JDM

The best approach is for an A/C experienced shop to put dye in the system and check for it with an ultraviolet light. This should identify the leak. Freon should always be in the system, like your refrigerator, and would never need changing, or adding. Its a sealed system. So flushing is for the engine cooling system, as you know, completely different system. Freon is a lubricant, so it is adviseable to use the A/C once a month or so just to lube the system up good in the winter months.. Seals tend to leak otherwise. A/c compressors do fail, like alternators, and waterpumps. Bearings go out, seals dry up...Make sure the compressor engages when a/c is turned on, noteable by a "click" at the front of the compressor. Check the a/c fuse for the compressor. there is an electric clutch on the front of the compressor that engages the pully when turned on. Another possibility to consider might be the ambient air temp sensors inside the car, but these are probably not the problem. Full cold setting should override these I believe.

velocess

Actually the system is not "sealed" like your refrigerator because it has valves. Those valves are put there for you to re-charge the system which is exactly what you should do. Over time as JDM pointed out, the seals leak. The trick is to keep the freon at the recommended level so that it will keep those seals lubricated and under pressure. Unless you have a significant leak, re-charge and enjoy.

JDM

velocess is right about the valves, they are there for maintenence, such as if any portion of the system needs removing for engine or a/c repair. Typicaly, a healthy system will never just loose the freon. Fortunately, the new stuff is cheap, so if there is a small leak, loosing it over a period of time is no big deal, unlike the old stuff that got up to $50 a pound! in light of what they charge to recharge the system, however, freon and labor, you'd do well to identify the leak also, hopefully save yourself anual visits to the a/c shop.

1999valkyrie

Thanks for the advice. I took it and took the car to a Goodyear repair center. They installed the dye, evacuated the system of old freon and installed new. They said they checked the function of all the parts and the system is working fine. It's blowing cold...they want me to come back in a month to check for leaked dye with the blacklight. All in all, $100. The dealer wanted $250.

Brian McL

If you find the system starts to loose it's cool over the next week and the Goodyear guy can't find a leak on the "visible" lines around the engine try to look inside the evaporator box (under the dash), not easy. They are a common cause of A/C failure in the 124......and expensive to fix...if you don't do it yourself. But a BIG job!! I know...I did one.

hangup

Hi Brian,

I might be in for one
I've added dye recently and i'm checking on it every night when it gets really dark outside. Can't really see much in the daylight.
My question is . . . if i don't find any definite leaks under the hood, is there a way to inspect the evaporator without completely taking the dash apart? Maybe i could open some plastic panels on the bottom and stick a UV light in there somewhere? I have a C43 but i figured there are probably enough simularities.
How many hours did it take to complete? MB dealers range from 20 to 30 hrs from what i hear . . . is it really THAT bad? Is it a job that one person could do or does it requre two?
TIA!

Brian McL

Try flushing the tray under the evap. out with water. Just stick a hose into the drain(s) from below. If the evap. is leaking the water should flush out the dye. There is R134a hydrocarbon based coolant substitute called Duracool out there that you can buy at some part /cooling stores and it has a distinct odour. If you smell it in the car after installation then guess what....it's the evap. The job took me 4 days...and it is tedious but with an above average knowledge as a DIY'er you can do it. Just take your time and pay attention to the pneumatic lines on the heater box doors. Sign on to AllData or get Mitchell on Line for a step by step. Disconnect the battery AND unplug the airbags. Passenger one on the 124 is under the passenger foot mat behind a metal panel. Good luck!

hangup

Wow Brian thanks that was QUICK!
Thanks for the info, i think it will come in very handy. I still hope it's some o-rings on the compressor or something . . . but i fear the worst . . . i fear it's the evap.

hangup

i think i found the problem. looks like a stone hit the radiator or something. right behind the fan. or maybe it was the fan that hit it or something.
it's a bit weird, the leak is right under the fan . . . the driver's side fan near the high side port.