A/C problem?!? - PeachParts Mercedes-Benz Forum

pr'ot hed · #1 08-06-2002, 12:55 PM

Good day to all...I'm having a problem with my 1990 420 SEL I hope someone can help me with. My A/C quit working gragually over the last week. The fan is intermittant, even if you select defrost, which usually goes to full speed and hot when selected. It's not cooling, even though the compressor starts and runs when placed in A/C mode and there's no bubbles in the site glass. I DID however get the system recharged with "freeze 12" back in early spring and it seems to have been working fine. Is there some type of control unit for this system or maybe a logic circuit somewhere that could have gone bad? Thank you for taking the time to read this thread and any help you can offer!! Larry :-)

#2 08-06-2002, 01:48 PM

I don't know specifically about Freeze 12 because the only alternate refrigerant I personally use is 134, but with most alternate refrigerants, the sight glass is no longer the guide that it is with its native refrigerant.

It will need to have gauges attached and a performance test done. The symptoms sound like there is a refrigerant leak.

Good luck,

pr'ot hed · #3 08-07-2002, 06:06 AM

Thanks Larry for the info...however I don't think the problem is with the refrigerant because even when the system had leaked down and the compressor wasn't running the fan still worked as usual. So I think the problem is else where. The low pressure switch hasn't opened and turned off the compressor...What else do you think it could be?..........thanks again for taking the time to answer! Larry :-)

#4 08-07-2002, 08:31 AM

What year and model are you working on? This information always helps.

Have a great day,

RPM55 · #5 08-07-2002, 08:05 PM

If the blower motor (fan) has stopped blowing the fist thing to check would be the fuse. The 126 cars have been known to crack the fuse and/or melt the fuse holder. If the fuse checks ok it's possible that the blower motor itself is faulty.

pr'ot hed · #6 08-08-2002, 09:56 AM

The fan works intermittantly...so I know it's not a fuse. If I turn the system completely off and wait a few minutes the fan "sometimes" will come on. But it still won't cool....Any ideas?

pr'ot hed · #7 08-08-2002, 10:39 AM

Larry, it's a 1990 420sel...

joe p · #8 08-09-2002, 07:40 AM

Visually check that fuse, and clean the ones in the front fuse box as well for good measure. If you find no problems there, check the klima relay after you establish that is has a static charge of 60psi.

Joe

pr'ot hed · #9 08-13-2002, 10:47 AM

OK...thanks!