The car is not overheating. I have A/C, blowing cool, a definite light cool, but it takes a long time for the car to be comfortable (not sweltering).
A/C compressor is turning, doing its job.
It was over 90 ambient. I pop the hood and the front fan isn't turning.
What to look for?
Any help is appreciated.

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85' 300D No inspection, No registration fees, Cheap insurance
"If my calculations are correct, when this baby hits 88 miles per hour, you're going to see some serious %$&^."

Should be a sensor to turn on the auxilliary fan when AC is running. I think it's on the high pressure side somewhere.
It's also triggered by high coolant temperature.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

You can test the fan by jumping the switch on the AC dryer.
Or, leave it jumpered allowing the fan to run whenever the key is on.

That was quick.
I don't know my a/c parts. The switch on the dryer? Is that something easy to get to?

__________________
85' 300D No inspection, No registration fees, Cheap insurance
"If my calculations are correct, when this baby hits 88 miles per hour, you're going to see some serious %$&^."

You can see the dryer when you open the hood, it is behind the passenger side headlight. The aux fan sensor has 2 wires going to it, I think they are blue and reddish brown. Take the 2 wires and connect them together with a paper clip and the fan should come on.

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

Not on the subject vehicle.

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If the a/c refrigerant level is more than slightly low, the fan will not operate; the refrigerant just won't get hot enough to trip the switch.

There are two switches on the drier. You want the upper one; should have wires permanently attached to the switch (aka pigtails.)

The W123 models never had that option.

I know we have talked about this before but let me ask 1 thing. What if your stuck in traffic and the AC is broken. Is the car just going to boil over, if you are correct about it not having a coolant switch that would really suprise me.

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

Yes. If the car has no A/C then the electric fan will just block airflow.

If it has A/C but its just switched off then the engine/engine bay heat can conduct into the freon and eventually trigger the switch.

What about certain 240Ds that don't even have AC, just heat. They have a aux fan, correct?

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

My 77 300d certainly behaved as if it had that option. The auxilliary fan would come on, on a hot day, even if the AC was not turned on.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The motor probably got so hot that it flipped the AC switch like forced said.

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

I changed my sensor when the threads broke. Now, it's on all the time, AC or not. My engine doesn't overheat, so I'm haven't been messing with it.

__________________
My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

It also might be a blown fuse. I had that problem this week.



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1984 MB 300 SD Turbo