Well, the compressor works. I jumped the switch and the clutch engages. I then put the wire leads back on the switch and the clutch also engages. There is about a 10 second delay between starting the car and engaging the compressor switch.

So the compressor works. That means the system has enough refringent pressure, all fuses and relays are OK, and the push button penal works as well, right? But it does not blow cold air. The search for a solution continues.

Bo,

Can you find a sight glass? I have never had to do anything with the air conditioner on my 124 car, so I don't even know where it is. I would look behind both headlights looking for it. If it has a sight glass, you will need to charge until the glass shows clear with no bubbles moving through it.

If you can't add enough refrigerant to clear the glass, you need to find a buddy with guages.

I think you're in better shape than you think. I still wish you would blow that charge, draw a vacuum then charge it. You apparently have all the necessary ingredients, a running compressor, r134 fittings, and apparently no significant leaks.

The 10 second delay after engine start is by design. It is so that the engine has plenty of time to build oil pressure before loading it.

There is another very real reason for drawing a vacuum. It serves to remove moisture from the system. Any moisture left in the system combines with elements in the refrigerant and produces an acid that will eat a hole through system components from the inside out. This phenomenon is much worse with r134 than with r12.

Given a vacuum pump, manifold guages and a canister of r134 or can tap with individual cans of 134, would not be a big deal to evacuate and charge. It would also give you an opportunity to put the correct oil in the system. The mineral oil used with the r12 will not correctly combine and circulate with the r134 which, of course, results in inadequate compressor lubrication.

If that car was in my shop, it would only take some ester oil, about 3 cans of r134 and about an hour for me to have it evacuated and charged, although I would prefer to evacuate it overnight to remove as much moisture from the system as possible.

Sorry for the sermon. As you can tell, by necessity, we probably have more experience with air conditioning in Texas than does the average Joe in Michigan. Of course, I'm sure that heating systems are a little different situation.

Good luck,

Thanks, Larry.

I think I will wait for a week to see if the pressure holds. If it does, then I am thinking about taking it to a shop to have it done your way, i.e., evacuate it and charge it with R134a.

In the interim, I wil get a gauge to see if the pressure is up to specs.

Thanks again.

OK,,,,, lots of people have spare ac compressors laying around ( everyone is a packrat , right? ).
They can not be used to make air compressors because the method of lubrication is by the flow of oil mixed with coolant....
How would one make a vacuum pump which could be run with an electric motor and could be left on over night to use for evacuating ac systems...
There must be some way to do this... I have about 6 good compressors... both types... could I place a reciever dryer with oil in it upstream of it? Do I need to tap the head and provide some metering device for small amounts of oil to be injected ? Could I use one of the turbo oil jets to spray the bore from the underside ?
I know this can be done, so no "it can't be done"s please,,,, It is just a machine and physics...I have seen old style ones which were good for long evacuations... they just dripped the water out of a hole...
And lets get those answers posted quickly as I am about to start on my new 240d's ac..LOL...
Thanks, Greg

Larry and David:

Thanks for your help.

For the time being, I am giving up on the AC.

I got a pressure gauge and there is plenty of refringent pressure (too much, as a matter of fact so I had to bled off a bit).

Now I am not so sure if the compressor kicks in as I tested in the ECON mode and it does the same thing.

The previous owner did honestly tell me that the AC was the last item that made her to sell the car. So I think there is something (big) wrong in the system.

Just have to live without AC on this car in Michigan. Luckily I have two others MBs that do have working ACs.