89 240 s/w. With the hotter weather, 90's and up, my car is running with the temp gauge right at the bottom of the 'orange' section at the top of the gauge. It hasn't boiled over yet, but does get right up next to 'overheat' on the gauge. The aux electric cooling fan does not come on when it's like that. There are 2 sending units on the side of the block under the intake, does one operate the gauge and the other the fan? If so, which is which? Or does the aux fan only operater if the a/c is on? I haven't decided if the fan circuit is inoperative, or if the gauge is inaccurate. I did jumper 12v to the fan plug and it did work. If the weather is more moderate, the gauge runs in the middle and all is well.
Any ideas? Or common problems in this area? I am starting to like this car (28 mpg) and don't want to ruin the motor.

dave

 

Mine has been doing that lately, but I don't think I even have an auxiliary fan...I'm contemplating removing the temperature compensator board for a few weeks and jumping the 1&3 pins to see exactly how hot the engine is actually running. Apparently this board is set up to indicate anything above a certain temperature as "overheating" There should be plenty of info about this in the forums if you just search for temp comp or something along those lines. Let us know what you discover.

 

Thanks 240wagon, I had been searching under cooling fan problems, hadn't even heard of the temp comp board. I will wire a bypass on it if someone can tell me where the wire should go. You said pin 1 & 3. is that just the wire connector to the board? I did the same thing to bypass the OD relay, poof! problem solved.

Dave

 

The aux fan will only come on when the AC high side pressure reaches a certain point. You can short across the switch so the fan always comes on with the AC, or wire it to a new switch inside the cabin so you can control it.

On the block one temp sender is for the gauge, the other for the ECU.

I would use a pressure washer on the radiator ... spray from the inside out.

Consider flushing the coolant and changing the thermostat.

See attached for the temp comp board bypass.

 

Good info, Bubba 240, thank you. I wondered about cleaning out the radiator, also. I will try the bypass and wash out the radiator from the fan side.

dave

 

The only thing that seems strange is I thought that the 240's didn't get the aux electric fan until 1991 .... hmmm.

 

I didn't get mine...and I thought my car WAS a '91. I guess i should look into that.

 

The VIN will show what the model year is.

Example out of Bentley: YV1AA8850L1851027

The "L" is the model year code. It is 1990.

M is 1991, N is 1992, P is 1993 (O is skipped)

 

Thanks. I'll check it out.

 

I have a 1992 240 and have a problem with the electric cooling fan as well. I directly applied 12 volts to the fan and it works. However it does not work when connected normally to the car circuitry. I have jumpered the high pressure switch as indicated in the above thread (at the switch connection) and the fan does not come on. The air conditioning does blow cold air but the engine temperature shows just below the orange band. Is there some way to ensure the fan comes on when the air conditioner switch is on?