Intermittent AC - PeachParts Mercedes-Benz Forum

tankowner · #1 06-07-2010, 12:13 AM

My 95' 300D has been having some AC issues - the cooling has been intermittent, but as of late it doesn't seem to be doing much at all. So, I start looking around. I remembered from last summer that one of the aux fans was on its way out, so I ordered one to replace. When it shows up I go to replace it and found neither of the fans were working. To make a long story short, I replaced one fan and got the other one working - quite a job

. Anyway, between the faulty fans and all the crap I cleaned off the condenser, I thought that was probably the culprit - unfortunately not. Both fans are operational and when I tested the AC the clutch initially engaged and it seemed like it started out pumping some cool air. The compressor ran for a while (10 minutes or so) and then just stop. I messed around with the climate controls but couldn't get it to come back on. What gives? Is this a clutch problem? What else could be going on here?

I'll hook the gauges up when I can and report the readings, but I thought I would try to get some feedback. Thanks.

ah-kay · #2 06-07-2010, 02:04 AM

If the A/C does not work. It is very very unlikely caused by the Aux fan. A faulty aux fan would give you inadequate cooling or over-heating the car. like it happened to me when I returned from Death Valley over Memorial W/E. It was a near death experience for my #14 head.

If your A/C cuts off after 10 minutes then works again after you switch off the car and back on again then it is likely to be a Kilma relay or loose connection. My take is a bad Kilma relay with a bad comparator circuit ( dry joints). You can try to jump the switch at the Recv/Drier to eliminate the high side pressure but I would doubt it is the issue.

tankowner · #3 06-07-2010, 03:26 AM

Quote:

Originally Posted by ah-kay

If the A/C does not work. It is very very unlikely caused by the Aux fan. A faulty aux fan would give you inadequate cooling or over-heating the car. like it happened to me when I returned from Death Valley over Memorial W/E. It was a near death experience for my #14 head.

If your A/C cuts off after 10 minutes then works again after you switch off the car and back on again then it is likely to be a Kilma relay or loose connection. My take is a bad Kilma relay with a bad comparator circuit ( dry joints). You can try to jump the switch at the Recv/Drier to eliminate the high side pressure but I would doubt it is the issue.

When it does provide cool air, it was often inadequate - so when I found that both aux fans were out, I suspected the problem was there. The no-cooling situation (apparently caused by the compressor cutting out) has grown progessively worse.

I don't think it is the Klima as I replaced a bad one a couple years ago and cured the problems I was having then. That's not to say that the used one I replaced with isn't now bad itself, but I'm inclined to think it might be a problem elsewhere. (famous last words) The AC doesn't necessarily come back on if I turn the car off and then on again.

I will try jumping the reciever/drier to see what happens. I did hook up the gauges prior to the aux fan fix and both low and high sides were reading high - IIRC it something like 45/275. I will try it again though. Thanks for the input.