A/C CUTS OFF/ WON'T KICK BACK ON

1991 SDL - AC will go off and sometimes will not come back on. When I stop and restart car, then it works. I do apparently have a leak no one can find (3 years, 5k). Last mechanic put on a shorter belt, but still same problem.

[5banger]

Sounds like a loose belt, maybe due to a bad tensioner. A circuit monitors the RPM of the A/C compressor and shuts it off after a sudden change (such as a slapping belt.) Turning the car off, and then back on, resets this. Pardon the late-hours reply, Andrew Seidel.

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89 190E 2.6
83 300TD Turbo
75 240D

[Mike Murrell]

As 5banger pointed out, you may have a problem with the A/C compressor speed sensor.
A loose belt is detected and the A/C compressor is shut off. You pull over, stop and retstart motor and A/C system and it'll work again for awhile until the speed sensor once again detects a problem. There's alot of talk about this in the archives. Do a search on "speed sensor".

Regards.

Mike Murrell
'91 300-SEL

Thanx for replies. The loose belt has been tried. The 2nd mechanic a week ago put on a shorter belt and put on a new tensioner. Yesterday at dealership the "freon" will filled and everything seemed to be working ok. Then off she went.

Is the ignition switch a possibility?

Thanx.

Dave

[Mike Murrell]

Just my 2 cents - I'd take it back to the mechanic who was last "under the hood".

Mike Murrell

[co.aulakh]

try the ETR relay.it is under the passenger side above the footwell.
clean the relay and presto.

[Benzmac]

Well, I would have to think that it is the speed sensor. The one thing to check to verify this...Just open the hood and see if the compressor OUTER FRONT CLUTCH is turning, if not, the compressor has been disabled by the relay. I have seen many people bypass the cutout.

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Benzmac:
Donnie Drummonds
300E
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Unplug the electrical connection to the Aux. Water Pump, then turn the system on and it will work fine... the same thing happened to my system - apparently there can be an overcurrent situtaiton via that connection which can shut the blower down. With the elec. plug disconnected you will still have heat and A/C. It will just take longer for heat - and not much longer at that.

quote:

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Originally posted by DESHAFFER:
1991 SDL - AC will go off and sometimes will not come back on. When I stop and restart car, then it works. I do apparently have a leak no one can find (3 years, 5k). Last mechanic put on a shorter belt, but still same problem.

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Jo