Ac compressor always engaged with climate control on automatic - PeachParts Mercedes-Benz Forum

MercedesOtto · #1 08-06-2009, 07:44 PM

I just fixed the AC on my 1982 wagon the first time and all works great, except that the compressor always runs when the system is set on automatic climate control. Even if it is cooler outside and the temp is on warm. The air blows warm but the compressor still runs. For economical reason the compressor should shut of if no more cool air is needed??
Is this normal?

kerry · #2 08-06-2009, 07:49 PM

Which button do you have pushed in on the climate control?

Jeremy5848 · #3 08-06-2009, 08:19 PM

Does the '82 have ACC II or ACC III?

MercedesOtto · #4 08-06-2009, 08:38 PM

Quote:

Originally Posted by kerry

Which button do you have pushed in on the climate control?

per owners manual the 3rd from the left (middle botton). If I psuh EC the compressor shuts of.

my wagon was built 12/81

Matt L · #5 08-06-2009, 08:44 PM

The compressor should shut off before the evaporator freezes, but that's it. The fan speed reduces and the air is reheated when the cabin temperature falls to the desired temperature.

If your evaporator isn't freezing, the system is working as intended. However, since (I think) you lack a variable-displacement compressor, I would expect the compressor to cycle some in cool weather. Perhaps you're just a touch low on refrigerant.

The manual for my '96 says that the AC compressor runs whenever it is above 37F outside, and that's what it does.

Chadahar · #6 08-06-2009, 09:02 PM

Compressor runs to keep from fogging the windshield among other things.

kerry · #7 08-06-2009, 09:07 PM

Quote:

Originally Posted by MercedesOtto

per owners manual the 3rd from the left (middle botton). If I psuh EC the compressor shuts of.

my wagon was built 12/81

Sounds normal to me. Just push EC if you don't want it on.

tangofox007 · #8 08-06-2009, 10:06 PM

Quote:

Originally Posted by MercedesOtto

For economical reason the compressor should shut of if no more cool air is needed??

That's how it works when you select an a/c mode. The sytem runs the compressor 100% of the time (unless the evaporator temp gets close to freezing) and regulates the output temp by "adding" heat, not by cycling the compressor off. If you are interested in economy, press the EC button.

Matt L · #9 08-06-2009, 10:16 PM

It is much more comfortable to ride in a car with this type of system. If the compressor cycles off, you get a bunch of humidity in the car.

#10 08-07-2009, 07:02 AM

It's amazing how many threads there have been this a/c season where folks must think that they're working on a Chevy. These are not pressure cycling a/c systems.

Jeremy5848 · #11 08-07-2009, 11:48 AM

Quote:

Originally Posted by LarryBible

It's amazing how many threads there have been this a/c season where folks must think that they're working on a Chevy. These are not pressure cycling a/c systems.

A good point that has not been sufficiently emphasized. The add-on air in my '65 Cutlass was a pressure-cycling system; you could hear (and feel) the compressor kick on when the thermostat called for it. I sometimes still forget that my Benzes don't do that.