1990 300ce Blower Motor Fuse Problems
 

About a month ago, while my GF and I were out cruising the Parkway, my blower motor stopped. Turns out the fuse strip melted on itself. For a quick remedy and to keep the lady happy, I put a glass fuse and.holder in on the side of the road. I used a 30 A fuse and thought all would be well. Alas, tonight my glass fuse and holder have let me down and melted again. What could be my cause and how do I prevent being known as the guy who used up all the 30 A fuses in the world?

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Yo ! Fellow Inhabitant of the Milky Way
 

1990 vintage Bosch Blower Motor "Bushings"
(NOT BEARINGS,AS WOULD BE SANE!)
The Damn "El Cheapo" "Bean Counters" not only "Shorted" US on Wiring Diameter
,BUT also specified Blower Motors with Narrow Little Metallic Bands INSTEAD of
Roller Bearings for the Blowers.

Scenario:

As the Bushings AGE they restrict the Rotation of the Shaft (Friction)
[SINCE the interface has NO LUBRICATION]
MORE FRICTION = MORE RESISTANCE ,
as the motor works to overcome the friction...MORE Resistance.
MORE RESISTANCE = MORE HEAT.
MORE RESISTANCE AND MORE HEAT = 30 AMP fuse BLOWING!!!!!!

The FSM calls for ATF as a lube for the "Bushings"
BUT,given all the Excrement to just get down to the motor,I'd
SOAK the Bushings for 24 HRS in 3in1 oil.

I know all this because:
My Blower Motor was replaced Less than 1,000 miles ago
It only "Draws" 23 amps D.C.

If I ever get "Down There" again,I'll look for a retrofit for BEARINGS and
post it.

HELL,given my current state of mind I'll modify an Electric Leaf Blower
mounted in the Trunk (and Plumbed to the engine compartment) to
Stand In for the BLOWER.

I think he's tryin to tell ya you need a new blower motor.

Search u-tube for mercedes blower motor videos which show how to access the blower motor. It's not easy, but do-able, especially after you watch the video.

There is also a blower resistor that sits under the fan. It must get pretty hot seeing as the heat sink is the size your foot. Fuse blowing caused by too high of resistance. Resistance can be from both fan motor bushings as well as overheating resistor.

If you go in to fix the blower fan, you may want to replace the resistor while your in there.

My blower was inop, but the fuse was good/blown resistor. BUT, fan was hard to turn so it probably cooked the resistor.

They use bushings because they are quieter than ball bearings, and do generally last a very long time. But I agree that sealed ball bearings would probably outlast the bushings. Still, this car is 23 years old and all the fan needed was some ATF on the bushings and away she flew.

I had some electrical gremlins that were somewhat related. Intermitantly, fuse #6 blew ONLY when the climate contol unit was used. The blower fuse holder melted on one occasion too! I went through 3 CCU's before finding a bad ignition switch (contact point) created high resistance in the circuit. The CCU's did not like the excess electrical draw along with the blower fuse. Replacing the electrical contact section of the ignition switch solved all the issues including fuse #6 which was not related to the climate control circuit. For me, that was the culprit!

I'm fearing my electrical gremlins may be vast. Occasionally random electronics (cluster, interior lights, fog, etc) wont work and the fix is to pop the fuse cover and run my finger over each fuse. None are blown and all have been replaced with new fuses. Next I will lightly sand each contact and apply some dielectric grease and see what happens.

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I just went through this on my E420 -- It was the blower motor. Last year, when I changed the regulator, I also oiled the blower because it was squeaking. I went through four strip fuses and found that it would only melt the fuse when it was in auto or high. DO NOT replace it with a URO motor. Get the Bosch or Behr. You will save yourself the hassle of doing the job twice.