I have an annoying problem that surfaced soon after putting a rad hose heater in my car. The small fan mounted in front of the rad comes on as soon as I turn the ignition key to the glow plug position, and stays on till the car is shut off. This is probably not a good thing for the winter months.

The car is a 1978 300d with the horrible auto climate control bs; may the guy responsible for that call be forever cursed. The unit is in "defrost only" mode and the air conditioning was removed by the PO

Is there a simple way to disable the fan? This might be a nice feature for the summer. I've thought of simply pulling a fuse but I don't have a fuse diagram and there is probably other stuff on that fuse I want anyways

Thanks in advance

Does the fan have a plug in wire at the fan? If so, with the key off pull the plug in wire and that should disable the fan.

It looks like it might be hard wired but once I clear some snow I will crawl under the car and hope for the best. Once I have this issue resolved I can start trouble shooting my only on really cold nights battery drain mystery

If the fan is hard wired you can always cut the wires and when you are ready to have the fan workable again use crimp on or solder type terminals.

Absent a field modification, you will find a plug 20" or so down the harness from the fan end. Removing the fan relay might be easier.

Do you have a temp switch on your receiver/drier?

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

The climate control.....is not that bad....don't know why people complain about it soo...pita to fix and expensive to fix....yes....but once going again and fusing the aux pump....so it doesn't blow the amp if it kicks the bucket it works fine....

As for your fan, you can unplug it from the drier on the passenger side under the headlight...or you can pull the relays in the box on the drivers fender....or you can unplug it behind the bumper or you can remove the fuse...

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I'll take a look inside the passenger headlight tonight, thank you

Ya all I see is a sealed cable running from the fan to the driver's side headlight, then it disappears into a tube with a bunch of other cables. I guess I have to cut it?

Follow the lead from the motor, there should be a small square connector clipped to the lower radiator support.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Will do tomorrow, it's a howling blizzard outside at the moment

has the fan always been on? if it only started staying on after you installed a rad heater, you may have bent or shorted the temp switch that brings it on. there is a temp switch on the top of the a/c drier that brings on the aux fan. if it's shorted together, the fan will come on as soon as the key is on.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

as for unplugging it, you've been given general directions to where the socket is... but it's really tucked under the frame tube under the headlight bucket beside the radiator support...
follow the fan wires, they will pass through a hole in the frame, and there is a clip on the inside of it, where the socket is. not easy to reach... it may be easier to just cut the wires feeding the fan, but there is a socket connecting the fan wire to the harness.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

It just started now so ya I would imagine the various shenanigans in the engine bay may have done something

Ok sounds like I need to crawl around under the car. I just need a day when it's not fracking ice planet both outside. The dryer you are referring to, is it a small tower like doodad on the front passenger side of the engine?

Only if you insist on doing things the hard way. It would be alot easier to remove the fan relay or (maybe) disconnect the wires from the receiver/drier.

Front passenger side of the engine compartment.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.