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Old 08-19-2001, 11:10 PM
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Question 88 420SEL A/C Repair Possible?

I have a 1988 420SEL with 115k miles. The A/C does not work properly -- the discharge air does not stay cool when the car is idling in traffic, but it does get cool when driving at freeway speeds. It acts like other cars I've had that needed a can or two of Freon, back in the old daze.

I am completely ignorant of the new regulations for A/C repair -- is it possible for me to get this air conditioning repaired as a Freon system, or do I have to convert to R134a? I've heard all kinds of stories from different shops in the Los Angeles area, and I could use your expert advice, please!

Thanks in advance... -- Jasper.
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Old 08-20-2001, 12:08 PM
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Join Date: Aug 2001
Location: Florida
Posts: 270
Check the sight glass on the receiver/drier at the front of the enging compartment drivers side. If the freon level is low you will see bubles in the glass when the system is on. If it's low take it to a licenced qualified repair shop and let them fix the problem.
If the glass is full is your auxiliary fan or fans on? Is your heater control valve functioning properly. I'm Not even to the novice catagory guy..these are just a couple of things shared with me in the past. Good luck
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Old 08-20-2001, 01:50 PM
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Yes, it does sound like you have lost refrigerant. It is totally legal, and usually the accepted method to recharge with r12. If you have some yourself, it is even legal for you to charge the system yourself. What is NOT legal is for a non certifed individual to work on someone elses car when R12 is involved.

R12 is EXTREMELY expensive these days. For this reason, you need to ABSOLUTELY ENSURE that there is no leak when you recharge the system. If it has gotten low, it stands to reason that there is a leak somewhere. You need to find a reputable shop, and let them look for a leak, repair it and recharge.

One of the alternatives is to convert the system to R134. My personal experience in changing MB's to R134 has not been good. I have converted American cars with no trouble, but the MB's have eluded my success.

Good luck,
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Old 08-21-2001, 05:33 AM
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Join Date: Dec 2000
Location: New Hampshire
Posts: 36
If your system is intact and fully charged I suspect your problem is with the aux cooling fans. These are more important than some might think. If not working, the high side pressure will climb off the scale at idle and on very hot days. The high pressure does two bad things. It reduces the ability for an effective heat exchange (hence the poor cooling), but also submits the entire system to a lot of high pressure stress which ultimately will cause component failure (ie: hose couplings, sensors, etc.) So if it isn't leaking now, and the fans are not operating properly, it will probably leak eventually. Not a good thing with an R12 system.

2002 ML500, 2009 CLK350 Cabriolet
93 300D 2.5 Turbo 265,000 Miles (Sold - bad idea)
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Old 08-21-2001, 07:06 PM
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Thumbs up Thanks for the great advice!

Thank you to everyone for replying to my question - I sincerely appreciate your advice.
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