Blower motor fuse - PeachParts Mercedes-Benz Forum

Aldbigt22 · #1 07-01-2019, 01:21 PM

So my blower motor fuse keeps getting hot and starts to smoke i have unplugged the motor and it still smokes. I have also unplugged the temp relay and still smoking. Dose anyone have any idea what could be causing this ? Sorry I guess it does help to know what cari have . It is a 1983 300sd

So I have used the 16a fuse and that was still getting hot and smoking with the blower unplugged i have also traced all the wires in the eng compartment to the fuse block and all is looking good there. I have not unbolted the fuse box and inspected under it nor have i unplugged the speed control at the blower. Now if i am looking at the master cylinder it looks like the resister is under it. Can this be ? And can the resister be causing the problem ?

DeliveryValve · #2 07-01-2019, 04:21 PM

Model and year?

Diesel911 · #3 07-01-2019, 07:42 PM

This is your first post.
Since we don't know what vehicle you have I will give some general info.

On mine the blower motor was full of crud and the rear bearing which is in my case a bronze bushing was also fill of crud and the Blower motor stopped turning. When the Motor has trouble turning it draws more amperage and that can exceed the amperage of the Fuse and or the Wires if you have the wrong Fuse.

So the Motor itself should be pulled and inspected.

Or you could have a typical short circuit where the insulation of a wire wore through and got ground.

When some motors wear out the brushes the brush springs make contact but that is usually noisy.

Motor and Stator windings can fail on their own often due to vibration but I have not read of that happening.

Depending on the year the Auxiliary Water Pump has no fuse but is connected to the climate control board. When that pump seizes up or has other issues it has been known to burn the control board and once I read it caused a fire in the interior.

Aldbigt22 · #4 07-02-2019, 12:42 AM

So it’s a 83 300sd and I did check the blower and it good

JHZR2 · #5 07-02-2019, 02:18 AM

The well known issue on w123 cars is the #8 fuse burning up when blower motor brushes go bad. I would assume similar vintage w126 cars have similar concerns.

Testing the fan might not be good enough. Ive had multiple w123 cars that have fine working ac and fans, but when the blower is on high, will blow the fuse. Can even start a little fire.

There is a bypass kit available that installs a strip fuse in the place of the ceramic one. Don’t know if we’re there yet on yours.

Since you’ve unplugged the motor and control, and things still get hot, I’d suspect you have another issue.

First off, what fuse rating do you have? It’s a red 16A fuse that should be used on w123s, consult the fuse box for the correct rating in a w126. Do not put a larger fuse in there. Ive seen blue 25a fuses put in and have seen them get hot enough to burn the paper and part of the fuse box.

Not knowing any other details, my first hypothesis would be that a fuse of too high a rating was used, it didn’t protect the conductors, one melted somewhere and you have a high impedance short. If it was just the motor (which I’d guess may have been an initial culprit), things would stop smoking when you unplugged the motor.

Diesel911 · #6 07-02-2019, 02:01 PM

A functioning blower does not mean it is not drawing more amps then it should.

I forgot to mention another issue. People have had issues with Fuses that have Plastic Bodies. The Plastic melts before the fuse dose and breaks the circuit.

JHZR2 · #7 07-02-2019, 02:41 PM

Quote:

Originally Posted by Diesel911

A functioning blower does not mean it is not drawing more amps then it should.

I forgot to mention another issue. People have had issues with Fuses that have Plastic Bodies. The Plastic melts before the fuse dose and breaks the circuit.

+1 to both. But key here is that when disconnected he use still smoked...

Assuming I interpreted correctly.

Diesel911 · #8 07-02-2019, 08:44 PM

Quote:

Originally Posted by JHZR2

+1 to both. But key here is that when disconnected he use still smoked...

Assuming I interpreted correctly.

We will have to wait and see what he finds.

Aldbigt22 · #9 07-03-2019, 12:26 AM

So I have used the 16a fuse and that was still getting hot and smoking with the blower unplugged i have also traced all the wires in the eng compartment to the fuse block and all is looking good there. I have not unbolted the fuse box and inspected under it nor have i unplugged the speed control at the blower. Now if i am looking at the master cylinder it looks like the resister is under it. Can this be ? And can the resister be causing the problem ?