Just took the blower out (which was a piece of cake!) and I can't locate the resistor(s)? My FSM shows them in the blower housing under the cover that the plug goes into, but it looks like a straight connection to me. It is a Siemens blower.

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1984 300TD 1981 240D

OK- I just located my handy dandy 1981 MB electrical troubleshooting manual, and it say the resistors are "above passengers footwell, in fresh air duct". I'll try again after a beer and some breakfast!

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1984 300TD 1981 240D

If you found the blower you are in the right neighborhood, look at the big black behemoth under the dash (the air box), it is in the bottom just to the left of the blower location.

It is a flat plate with electrical connections.

Note that it relies on the air flow to cool it...so the actual resistor elements are on the back of the plate. They look like springs but beware they get hot when under load.

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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

I found the connector to the left of the blower, but the wires to the resistors go behind the center of the dash and I cant find where they lead to I tested the output from the switch and it works fine so it has to be those da#* resistors.

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1984 300TD 1981 240D

sounds like pre-switchover to me. look under the cowl cover. they're just about straight under the wiper motor.

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- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

I will try that right now! I got interrupted by my son being in an accident, and I had to go pick him up Everyone was OK except the cars, so all is well and time to get back to work!

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1984 300TD 1981 240D

OK- I still can't find them. What do I have to remove to get to these magical resistors? I have the passenger side cover and the glovebox removed. Do I have to take the whole evaporator box out? Maybe more beer will help! Regarding the switchover thing, there is a switchover valve under the dash to the right of the glovebox.

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1984 300TD 1981 240D

Look at the bottom of the air box, near the center of the car, from the right side under dash access area.

There is a 4-pin connector C134 in the under side of the air box.

You can follow the wires from the blower motor, they end up on this connector.

Behind this connector is a metal plate, the resistors are inside the box in the air stream.

__________________
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

The 4 pin connector is on the front of my air box. From there the wires to the resistors disappear to the middle of the dash. To get to the resistors it seems I will have to disassemble a whole lot of stuff unless I am just overlooking something. I think I'll just jumper the wires at the connector to bypass the resistors for the time being.

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1984 300TD 1981 240D

Did you look under the cowl cover? It's that metal plate outside of the car between the two cowl vents. Removing it involves pulling the wipers, cowl vents, and then the plate is held down with a nut on the passenger wiper pivot, two screws and four plastic pushpin fasteners.

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

I haven't tried that but it sounds like a great idea! Have you done the resistors this way?

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1984 300TD 1981 240D

Can't say that I have, but I just replaced the wiper motor on my '77, and got my screw driver tangled in them when I dropped it. My resistor assembly still works. (knock on Zebrano!)

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

To follow up on this subject- K.C. was spot on. To get to the resistors you have to take the cowl cover off and they are right there! Unfortunately that wasn't the cause of my problem and it turned out to be the switch (which I thought I had properly checked, but I was wrong). Oh well, I now have one more bit of knowledge on MB repair. Thanks to all who helped- Scott

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1984 300TD 1981 240D