I would still dispense by weight. Do 80 percent of what the car calls for. I can't remember anymore. Was it 2.2 lbs of r12?

Why don't you just retrofit the complete r134A set up they used when Mercedes converted the 124 chassis from R12 to r134a in 1992 and 1993?

My 1993 300E (3.2) "E320" had r134a from the factory, and it had the coldest a/c of any car I've ever had.

I took it to Vegas and Palm Springs several times when it was 20 million degrees F, and it always blew ice cold.

That is the long term goal, but with R12 instead...It would be even BETTER :)

Condenser swap is definitely the first and most important part. I feel like no amount of cleaning could make me feel comfortable that it is shedding heat quick enough. Plus, the updated one could be larger.

Next weekend I will install the new condenser.

My '72 280SE 4.5 had been converted to r134a by its second owner (I'm the 4th owner), and it blows ice cold in any temp.

The entire a/c system has been replaced: compressor, condenser, evaporator, lines, fittings, even the switch in the dash.

One clue to its effectiveness is the huge condenser that was put in.

Mounted on the new condenser!

http://www.w124-zone.com/downloads/p.../fanmount2.JPG

Didn't the later models have two modes of fan operation? How did they achieve this exactly?

PM Arthur Dalton. He'll know.

I do know the fans spin together, either on low speed or high speed.

2 speed fan
 

There is a double coil resistor mounted just rear of the left headlight assembly. I don't know the part number. Low speed is triggered by the pressure switch on the receiver/dryer, and high speed is triggered by a temp sensor on the head.

Well I jumpered 30/87 relay K10 as suggested by Arthur Dalton and the low speed worked, I then jumpered the pressure switch with Key ON and it worked too.

I need to measure high side pressure, but last year when I did it, I was reaching 360psi high side and it still would not kick on, so I assume the pressure switch is toast. I have a new switch in my parts box anyway from a long time ago, so I'll swap it anyway.