300E, A/C CutsOut, Foggy Windows

[joel]

am still hunting why my a/c compressor cuts out
and thus fogs up my windows. alls well when engine
restarted until compressor cuts out again.
have checked belt tension, and belt tensioner.
speed sensor and low freon switch are okay.
what else, any suggestions?

When you say, "Cuts out" do you mean that the Blower Fan stops working or the A/C compressor fails to engage?

I have the same question as Roas. To help with the fogging, apply rain-x anti fog. that will help. but it doesnt really directly answer your question.

[joel]

cuts out - the compressor fails to engage.
Normally, the a/c compressor re-engages
depending on your desired temp. Mine will
work fine then will cut out until engine is
re-started.

[stevebfl]

On the non-technical side of this issue. I believe MB originally designed the system solely for their own purposes.

The point is to protect the belt from a seized compressor. As far as I'm concerned this is only a problem during the warrantee period. I can not see a consumer driving a car with a seized compressor unless they figure MB is going to pay for all the problems they creat in the process of not being inconvenienced.

As a result of being protected from such abuse, we (technicians and consumers alike) have been faced with tempermental, intermittant, A/C problems that place many in discomfort. I would gladly give up all I have made fixing these problems to not have to face another of these intermittants on a 95 deg Florida summer day.

I say this after fixing hundreds of them. If I owned one I would bypass it at the first sign of intermittant behavior. I do not do this in the shop, but I would on my own car.

MB has finally given up on this system. They now approach it differently. They put a thermal fuse in the compressor clutch. When the compressor seizes the fuse blows as the pulley heats up. No more speed sensing. Thank You!

[joel]

thank you Steve. as a matter of fact my independent
MB mechanic suggest to by-pass the system. i am just concerned about this by-pass procedure. i know you
are generous in your replies. could you explain
in non technical terms what exactly will be by passed
and will it not affect the performance and value of the vehicle. thanks a lot.

[stevebfl]

The large A/C compressor control relay "Klima" uses numerous inputs to justify the A/C clutch on/off decision.

One of those inputs is the control signal for the compressor from the pushbutton controller. The necessary by-pass would use that signal alone to control the relay. The whole relay could be rewired using a simple relay and the necessay circuits or the "Klima" relay can be disected. I have altered a number of these relays to be tools. The other signals can be over rided with a simple wire soldered over that section of the relay.

You will want to by-pass the engine safety controls, not the A/C controls. Running the relay straight from the ignition only will cause the system to freeze up. All the A/C needs are handled by using the control signal to activate the relay.

[chowpit]

I wouldn't rule out the possbility of the evaporator freezing up. The fogging that you get could be from the moisture coming through the defogging vents as the evaporator thaws. Plugged A/C drains or a faulty evaporator temp sensor are possible culprits.

[joel]

thanks again steve for your reply.

scott: thanks for the tip. will check
possible plugged drain. where is the
evaporator temp. sensor located?

[ctaylor738]

Here is series of posts from last year on how to deal with this problem.

Good luck!

GERMAN AUTOMOTIVE
Member
Posts: 15
FromALMDALE CA. U.S.A.
Registered: Mar 2000
posted 03-17-2000 03:44 PM
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THE COMPRESSOR RELAY CAN BE BYPASSED AS FOLLOWS,USING RELAY # 001 542 02 19
MAKE YOUR OWN JUMPER WIRES. TERMINAL #1 ON KLIMA TO #85 ON ICE CUBE,#10 KLIMA
TO #86 ICECUBE ,TERM. #5 KLIMA TO #30 ICECUBE,AND #7 KLIMA TO #87 ICECUBE.
CLUTCH WILL ENGAGE AND DISENGAGE AT PUSHBUTTON ASSY'S COMMAND.M.F.
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M.F.

IP: Logged

BRAD
Member
Posts: 11
From:SUMNER, TX 75486
Registered: Mar 2000
posted 03-17-2000 04:48 PM
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THANKS TO GERMAN AUTOMOTIVE M.F. WILL THE COMPRESSOR STILL BE CONTROLLED BY
THERMOSTAT CONTROL WHEEL? ALSO WHAT ARE YOU REFERRING TO AS ICECUBE?
------------------
BRAD FRANCIS
1986 190D 160,000 mi.
SUMNER, TX

IP: Logged

Benzmac
Moderator
Posts: 3251
Fromuluth, GA, USA
Registered: Mar 99
posted 03-17-2000 09:11 PM
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I have had to do this with 134 conversions because of the higher pressures.
It does work. The ice cube is a generic term for the Bosch 5 pin relay. You
can get one at any stereo shop... It will be controlled by the pushbutton and
will cycle on and off yes./.
------------------
Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

[joel]

thanks chuck for the info. will pass in on
to my mechanic. hope he can follow through.

[joel]

culprit is loose sensor atop the a/c compressor.
yes, i prayed and was guided accordingly. cheers!