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.

By "shuts off" do you mean the cabin blower stops functioning? Or do you mean the compressor disengages?

The cabin blower definitely shuts off but I'm not sure if the compressor disengages.

Nick

Sounds like you may need to look into resoldering your PBC unit - do a search, there's plenty of info here.

Thanks for the info
I will search

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

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.

Anyone know where the electric pump is?
Can I just unplug and disable the pump with no adverse consequences?

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.