81 300sd blower motor running at 16.1 amps - PeachParts Mercedes-Benz Forum

ibenz · #1 05-29-2012, 02:37 PM

I blow my 16 amp fuse after a few minutes of running. i read somewhere on here that it should possibly be a 25 amp fuse in my model. Is this correct or is the red 16 amp fuse correct... i pulled my brushes today and they are less than half an inch long so since there out i am replacing them.... there is some grooves worn into the brush ends....

this is what i found on the amp range for a 126 compared to a 123....this was mentioned by whunter

Here is the data you need.
Blower Motor Links Page
Blower Motor Links Page

You must add a fuse to the new fan circuit...
If it is 12v -14.5v the blower will work fine, excess amps can toast it quick = fire...

The W123 OE Blower Fuse is a 16 amp.
The W124 and W126 model OE Blower Fuse is a 25 amp.

MB issued Service Information Letter 54/13 dated March 1987.
This is a kit to separate the blower motor circuit onto a 30 amp external fuse housed in a separate weather-pack holder outside the fuse box.
The SIL also required replacement of all the 25 amp fuses with newer "solder tip" 25 amp fuses part no 001 545 75 34.
This mod was for 124 and 126 models only.

I do not recommend retrofitting this kit to a W123 model.
If your W123 is blowing that fuse, then the blower motor is in need of new brushes or possible replacement.
A larger fuse will not solve your problem - and you might create a fire under the dash and that can ruin your whole day . . .

jay_bob · #2 05-29-2012, 02:57 PM

I am having the same problem on a 240D.

You are correct the retrofit kit is not for W123.

If you pop a 16 A fuse there is something wrong with the motor. Using a 25 A fuse or the 30 A bypass fuse will cause you a real hot problem

Lube the bearings and check/replace the brushes.

Funny story from my last trip to VStech's last weekend, we were looking for something to support the fan while tapping out the motor shaft, turns out a 617 cylinder bore in the block (with the head removed) is the perfect diameter to allow the motor to hang down, while the fan rests where the head normally goes...

if you just so happen to have a 617 block lying about like VStech does...

jay_bob · #3 05-31-2012, 07:08 PM

VStech posted the picture of the "blower fan removal jig" aka 617 block in another thread.

To everyone else considering using the 126 fuse upgrade on a 123 please no don't do it!
Your wiring cannot handle being fused at 30 A.
If you are popping 16A fuses on high speed do not over fuse to 25 or 30 A.
You have a problem with your blower.
Fix the blower (either pull and lube and check brushes or use Volvo motor) then put in a new 16 A copper/ceramic fuse.
If your #8 fuse clips are toast then move the wires on the back side of the fuse board to an unused fuse or rig a correctly rated external fuse holder.

Anything else runs the strong risk of your car becoming a car-b-que.

Pooka · #4 05-31-2012, 08:13 PM

I bought an old MB long ago and when driving it home it acted and smelled different. It was the sort of thing that was hard to put your finger on.

I finally checked the fuse box and found most of the fuses wrapped in tin foil. A little sorting out and I found no electrical problem, so I called the guy I bought the car from and he told me someone had suggested this to him as a way to prevent fuses from blowing.

I have to admit if keeping fuses from blowing is your goal this would work, but if you have a real electrical problem someday..... Well, I guess if you had a real electrical problem someday then all of your troubles would be over! At least with that Mercedes.

ibenz · #5 05-31-2012, 08:15 PM

just went ahead and replaced blower motor and solved all my issues... runs more quiet and works very well.

jay_bob · #6 06-04-2012, 07:50 PM

I did the fuse box wire move trick yesterday. The new fuse runs cooler but still a little warm. I will keep an eye on it and go the bypass route if this doesn't work out.

From my experience with fuses and breakers, they are allowed to get warmer than you think would be good. Just because it is hot to you does not necessarily mean it is bad. Temperature rises of mid 100s F and above are not uncommon and completely normal in my world.

If I can get hold of a FLIR camera I will see if I can give it a scan and see how hot it's getting.

I think I am ready to try out for cirque du soleil after doing this.

-disconnect battery
-drop lower driver dash panel covers
-pull cruise amp, (10 mm bolt inside the brake pedal bracket) this gives you much needed room
-double check you have disconnected the battery
-remove 7 mm nut at bottom of fuse block
-go up under the dash (recline seat fully, your head goes where your feet normally go and your feet where your head goes)
-quickly before you pass out reach up there and pull the fuse panel into the dash space. There is enough slack in the wiring that the fuse panel will drop down nearly to the floor board.
-you should see that fuse #5 has 2 studs that are completely empty. You will have to "part the Red Sea" to find it.
-transfer the two wires from #8 to #5.
-push fuse block back up to hole in upper dash. The top has 2 hooks that grab into the edge of the hole, make sure they are properly engaged!
A helper is very helpful for this.
- carefully check that you have no wires touching the frame
-put the bolt at the bottom back in
-reconnect the battery
-put cruise amp and lower dash back together