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  #1  
Old 10-09-2008, 12:55 PM
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Join Date: Jun 2008
Location: Chesapeake, VA
Posts: 138
91 300E A/C Gremlins

Hey everyone!

I really need help with this one.
My A/C works for approx. 10 minutes after startup then shuts off suddenly. It may shut off while driving straight but most often during a turn. The air recirculating button also becomes inoperative and HOT air blow from the windshield vents as if the defrost is on.
For the last 2 months it did not work at all. Then one cold morning 2 weeks ago, it started working after hearing some vents close; shuts off after 10 minutes and then starts working again if I shut the car down and restart within 5 minutes.

Any Ideas?
All fuses are good.

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  #2  
Old 10-09-2008, 01:37 PM
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Join Date: Sep 2004
Location: DFW / Collin County Texas
Posts: 1,882
By "shuts off" do you mean the cabin blower stops functioning? Or do you mean the compressor disengages?
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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
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  #3  
Old 10-10-2008, 08:18 AM
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The cabin blower definitely shuts off but I'm not sure if the compressor disengages.

Nick
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  #4  
Old 10-10-2008, 09:40 AM
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Location: DFW / Collin County Texas
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Sounds like you may need to look into resoldering your PBC unit - do a search, there's plenty of info here.
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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280
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  #5  
Old 10-10-2008, 09:47 AM
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Location: Chesapeake, VA
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Thanks for the info
I will search
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  #6  
Old 10-10-2008, 10:44 AM
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Join Date: Jun 2000
Location: Plano, TX
Posts: 2,529
What you describe sounds like the protection mode the pushbutton unit enters when the auxilliary electric water pump is shorted out. The electric pump pushes a steady flow of hot water through the heater core so that consistent heat is available whether the engine (and hence the engine driven water pump) is running at idle or highway speed. Unfortunately, I don't know where the electric pump is located on your 124 chassis w/M103 engine. Hopefully someone familiar with your can will chime in and identify it. There is an electrical connection which you can just unplug to disable the pump.

Do you live in a mild climate where after 10 minutes the a/c has fully cooled the car? If so, the pushbutton brain will start to mix in some heat (warming the cooled air) to keep the interior from dropping below the set temperature. Whenever the brain calls for heat, it activates the electric pump - and immediately goes into protection mode.

- JimY
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  #7  
Old 10-10-2008, 04:49 PM
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Location: Chesapeake, VA
Posts: 138
Thanks for that advice. Sounds logical and a friend of mine has already has mentioned that pump.
Here's a new twist.
The A/C has been working well with no shut downs ever since I posted the original post. The weather has been in the 80s and it's been working perfectly. I'm actually waiting for it to stop working.
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  #8  
Old 10-10-2008, 04:51 PM
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Anyone know where the electric pump is?
Can I just unplug and disable the pump with no adverse consequences?
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  #9  
Old 10-10-2008, 06:12 PM
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Join Date: Jul 1999
Location: Jax, FL
Posts: 1,785
It is just under the coolant reservoir...

on your left hand side looking at the car from the front. It has coolant hoses attached to it.

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