My 1990 300e is overheating but only when the ac is on blast and car is at idle once I start moving of turn the a/c off it cools back down to about normal temp between 80-100. My coolent is topped off and I replaced the thermostat already and it still does the same thing any other ideas or has someone experienced something similar ?

Thanks in advance

Check to make sure that the fans in front of your a/c condenser (next to the horns) are turning on. They should come on just after you turn on the a/c..

__________________
03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio

If all is working like above post . Then you could replace the thermostat for one to open quicker on a lower temp .

Wow idk how but that idea completely fly over my head lol I will check that first thing tomorrow

Ok so after checking out the fans that I completely forgot about before posting this thread lol I noticed that only 1 or the 2 fans will turn on which is the right side (driver side) is this a pain in the ass job that requires me to remove the radiator to install a new one ? Just Trina get an idea of what I'm getting myself into before starting the job

I would take a look at the fan clutch before anything else to see if it's locking up when the engine is up to temp. If the engine is hot and you can stop the fan with your hand, it's not working or you can hear it when the engine is revved up. A pretty common problem on the 103s. you may want to use a pair of gloves

I already figured out one of the fans on the radiator isn't cutting on. Thanks for ur input on how to lose a finger

Search for a thread started by me a couple of years ago - auxiliary fan failure analysis. To remove the auxiliary fan frame assembly there are four radially oriented screws at about the 10, 2, 4, and 8 o'clock positions. The radiator does not need to be disturbed, but it's much easier to access the fan frame screws by removing the front bumper assembly first, which is quite easy. There are four nuts on each frame horn, plus 10 mm head screws that hold the bumper surrounds that you access from the wheel wells.

You should also test the mechanical fan clutch. When cold the fan should rotate easily, but at over 100C and you stop the engine it should be much stiffer.

The aux. electric fans are energized by two sensors - one that engages them at full speed when the coolant temp reaches 105C, and a pressure switch in the AC system that energizes them at half speed by dropping the input voltage via the ceramic encased resistor mounted on top of n the LH frame rail.

Duke

Ok guys I figured out the reason for my over heating and it's being caused by the radiator fans not cutting on. Only one turns on but only once I turn on the ac. So if no ac nothing turn on and with ac only 1 of the 2 cut on. I'm assuming it's something with the wires? Cuz the fans (atleast 1) I kno for fact work just don't turn on when they are suppose to

Electric fans are used for the a/c system. The fan on the front of the engine is the one that attempts to keep the engine cool. Running a/c with just one fan can cause the issue if you run the a/c. Get both fans back in operation. You will be surprised by the amount of trash, leaves, etc.. that will be stuck in behind the plastic piece when you get it apart.

__________________
Jim