I have a 1983 300 sd. I got the a/c and heater working well about three weeks ago. Yesterday there was no blower motor. The fuse is fine (although it has been hot). I would appreicate any input. I have not found any info on the blower motor relay or it's location. Thank's in advance. Bill

Which Fuse?
F10 is for the Temperature Controller and Pushbutton Controller
F11 is for the Blower Speed Controller. Have you tried connecting the blower motor directly to 12Vdc?

Usually, what happens to the blower motor is worn brushes. You can replace the brushes but I found that may only buy you a little time before the motor ends up needing replacement, due to a worn armature.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Haven't dealt with it yet, but there is a resistor pack that controls blower speed. It is in the engine bay near the front of the passenger fender. Used to cost big bucks (~$300), but I got a spare at JY for $6 a month ago. In most cars, when the resistors fail, the blower stays on high speed always, but don't know about my 300D.

There is no relay.

The lack of a blower can be due to one of five possibilities:

1) The blower motor itself.
2) The resistor pack which controls the blower speeds
3) The blower controller which controls the resistor pack
4) The CCU which controls the blower controller
5) The temperature switch under the hood which controls the CCU. If the switch does not close, the CCU won't start the blower.


The very first thing to do is to drop the passenger side kick panel and expose the plug for the blower. Apply 12V and ground to the plug and see if the blower runs. If the blower does not run, you found your problem with the motor and need to replace it. If it does run, report back and we'll do further tests.