I have '92 124 2.5 turbo diesel. The auxilary fan will not come on. Fuse is good, in line fuse is good. It will run if I run 12 volts to it. I grounded the wires running to the high pressure switch and the fan did not come on. The wires feeding that high pressure switch have VERY LOW voltage to them as they made my test light glow but barely! I need this fan to work so my AC pressures will be correct. TIA Ernie

you sound way ahead of me on this but i just learned that if low on freon the aux fan wont work.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I don't think there's any freon in my system at all ....and my fan still comes on around 95C so I think it is tied to its own temp sensor/relay, as my A/C system is completely non functional.....

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well that is what the tech told me. he could be wrong. or different models could be differently wired. come to think of it i thought at the time it sounded funny. but in any case before the trip to the ac shop the aux fan didnt work and now it does.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Why did you ground the wires? You should connect them together without grounding them.
Take a trip to Radio Shack and get a 1' length of insulated wire and 2 alligator clips and make yourself a test wire.

Danny

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1984 300SD Turbo Diesel 150,000 miles

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Danny: I misspoke. I bridged them together. Sorry. Ernie

On some models the aux fan is turned on only by excessive high side pressure while on other models it is also turned on by high engine coolant temp.

On either model it is totally possible in a mild climate for the car to live its life without the fan ever coming on. In my climate where we always see temps in excess of 100 degrees Fahrenheit in the summer, the fan will indeed come on from time to time.

Have a great day,

There's a pressure switch on the drier that I shorted together to get my fan running.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
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'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
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'83 Harley Davidson FLTC (Broken again) :-(
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I noticed there was almost no voltage at the high pressure switch when the engine was running and almost 12 volts when the ignition switch was on and the engine was not running. I bridged the wires at the switch and turned the ignition on and the fans started running. I started the engine and they continued to run and the air condition became much more efficient! After a few minutes I turned the car off and wired the high pressure switch back in the circuit and started the car. The fans started RUNNING and cycling with the high pressure of 200 on the high side. I must have "jolted" the relay? So far it has been cycling all day and cooling much more efficiently. I'll keep my fingers crossed. Thanks for the tips. Ernie

Ernie,
I have a similar problem with the fan. How did you bridged the wires? On my e300 the dryer has 2 mounted sensors: one has a 3 wire connector facing the passager wall while the second (is lower than first) 2 wire connector is facing the from bumper. Which one did you bridged?
PAT

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pat201