No A/c Help!!! - PeachParts Mercedes-Benz Forum

#1 07-20-2003, 05:09 PM

89 560SL First it was Intermittent. After starting the car, the AC just would'nt come on. I tried alternateing on and off ac switch and sometimes AC would come on sometimes not, sometimes it would opperate fine othertimes it would cut out after a bit sometimes it would come back on. I even tried (with about the same success ratio) restarting the engine at stop lights. That was last summer. This summer it blows hot air only. It seems to be hotter off idle than at idle. Also the center vents are not as hot as the outside vents???? I have searched the forum whith out any discussion matching my symptoms
Somebody hep me please.....

cbdo · #2 07-20-2003, 05:15 PM

I've had the completely-dead-system thing happen a few times quite randomly. Another board reported that worn accessory contacts in the ignition switch can do it; you might try replacing just the rear contact assembly and see what's still going on after that, as the part is quite inexpensive. Haven't done mine yet, as the symptom has been rare, but after that last bit of info I intend to.
If there's still a hot-air-only problem once the system is actually running, and you can verify the blower's operating, the monovalve is most often the problem; there's an easy and inexpensive replacement for the monovalve core.
Good luck and hope this helps!

#3 07-21-2003, 07:42 AM

I have seen this caused by a bad ignition switch on 123 cars, but I don't know if the switch in your big bodied car could offer the same problem.

What came to mind first when reading your post was a slipping belt. There is a sensor on the compressor that will shut it down in the event of a slipping belt. If there is oil on the belt or a weak tensioner this will occur.

Good luck,

cbdo · #4 07-21-2003, 08:13 AM

Larry, I've had no indication at all of belt issues. Both of us have SL's; do we have the same AC mechanicals as the SEL?