Maximum voltage for heater fan blower motor?
 

Does anyone know what the maximum voltage is for the fan blower motor for the in-dash heat/defrost etc. ?

I just want to bypass the dash controls and just get the fan blowing, but I suspect strongly there is an unspecified amount of resistance added by MB to drop the voltage from 13.2 v

And or do any of y'all know the resistance that MB uses ?

Thanks!

Car model and year? We can only assume it is some model of Mercedes-Benz.

Answer:
 

Here is the data you need.
Blower Motor Links Page
http://www.peachparts.com/shopforum/diy-links-parts-category/212324-blower-motor-links-page.html

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 . . .





Have a great day.:D

124 Blower motor not working again
 

I had the squeaking last week, now no motor at all.
This happened a couple of years ago and I did all the testing , grounding some lead and the blower motored was fine. I ended up replacing the regulator.

Could it be the motor stops freezes up and then blows with regulator. I will do the test again today to see if is the motor or the regulator.

Either way I have very little heat coming for the cold weather predicted this week.

Mike Sheehan
1992 300D -- 218K

Hmmm
 

No, the fuse should blow, before the regulator is damaged, unless the regulator coils are seriously corroded..

Note:
You can jumper/bypass the regulator = gives full speed blower.

Thanks for the input.

Here is what I have noticed, the voltages are all correct at the connector near the brake reservoir.

I ground the blue wire and the fan spins at a high rate.

I had the same thing happen last year and I replaced the regulator and the problem went away. Maybe I have the wrong fuse in there?

Other ideas?

Mike Sheehan
1992 300D - 218K