engine over heating when air conditioning is on.
 

Hi I have a 1994 c280 (202) and my car is over heating when the air conditioning is on, it doesn’t redline but it gets really close. Any ideas on how to fix this problem would be great. Thanks Ray.

Two basic things, the main issue is general cooling system condition and operation. You might take it to a radiator shop and ask them to pressure test it. They usually charge nothing for this. When the a/c is on it is in hot weather and the condensor in front of the radiator adds heat to the air that makes its way to the radiator, so it is naturally going to run a little warmer than in the non a/c months.

Secondly with the air conditioning turned on and stabilized, the aux fan should come on.

How hot is it getting?

Good luck,

check the aux fan fuse for starters.

The engine temp reaches 120c and the aux fans do not turn on.

the aux fan fuse is that located in the trunk of the car? i cant seem to find anything under the hood.

Jumper the pressure switch on the reciever/drier [ the one with the pig-tail leads ] with a/c on and see if Aux Fan comes on.
If Yes , fan cicruit is OK , you have a low refrigerant or pressure sw problem
If No, Take six screws around fuse box off to get to relay compartment behind fuse box There are two fan relays , Look on top of them ..possible fuse problem....
If No, check connections at dropping resistor behind driver headlamp.. this if part of aux fan feed circuit to fan motor/s..

it was the to relay fuse that were blown. Thanks for all your help you people are great. thanks again Ray.

FIY.
Benz has OKed that fan fuse be upgraded from 15 to 25A on dual fan models

The low refrigerant pressure switch does not control the aux fan, it interrupts the clutch to save the compressor. The high side temp switch is what turns on the aux fan.

Your help is appreciated and I'm sorry to split hairs, but I just wanted to save someone the confusion.

Have a great day,

I already split the hair for him , Larry.
There are two pressure switches on the drier on his model, so to save the CONFUSION, I purposely identified the High side pressure sw. with the pigtail wire notation included in the test procedure. [I even put the info required to differenciate the switchs in brackets for him].. The other sw does not have a pig tail wire set-uo, it has direct spade terminal connectors.
I sometimes use the Benz designation part ID #s , but I have found that to be of little use for the average poster, so a visual discription [ie- pigtail ]works fine here.
So good of you to correct the post, though.. next time I will go to futher lengths to include more detailed sw ID.

Thanks