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2014 ML350 W166 - I've gone into the battery compartment where the 40A Blower Motor Fuse is located. However the fuse block is "hidden" next to the battery in a cubby hole there. After removing the battery there does not appear to be any way to access the fuses. Can someone give me some advice on how to access the Blower Motor Fuse without removing the entire floor board and passenger seat?
I ended up getting a replacement blower motor assembly (including the resistor module). Installed it and all is fine.
As a heads up for anyone reading this thread... I replaced the control resistor twice before installing a whole new blower motor. Both of the replacement resistors blew in a very short period of time. First one was within a few days with with intermittent failures over that period. The second one blew within minutes.
After pulling the original blower it was apparent that there was far too much drag to spin the fan body. Given this is a 12 year old car and 130K miles I am not surprised that the bearings went.
I never did figure out how to access the 40A maxi-fuse on the fuse block next to the battery (Underneath front passenger seat). If anyone comes up with a method to do so it would be good to educate the rest of us on how best to access that fuse block.
I ended up getting a replacement blower motor assembly (including the resistor module). Installed it and all is fine.
As a heads up for anyone reading this thread... I replaced the control resistor twice before installing a whole new blower motor. Both of the replacement resistors blew in a very short period of time. First one was within a few days with with intermittent failures over that period. The second one blew within minutes.
After pulling the original blower it was apparent that there was far too much drag to spin the fan body. Given this is a 12 year old car and 130K miles I am not surprised that the bearings went.
I never did figure out how to access the 40A maxi-fuse on the fuse block next to the battery (Underneath front passenger seat). If anyone comes up with a method to do so it would be good to educate the rest of us on how best to access that fuse block.
Your blower dry bearing kept burning up its speed control module...
There is more as to why the blower ballast module "resistor" gets toasty hot - IT NEEDS COOLING AIRFLOW !!
How is that...
the $10 cabin air filter needs scheduled replacement to keep air flowing and "resistor" cooled.
Last edited by CaliBenzDriver; Feb 26, 2026 at 05:35 PM.
This whole process of replacing control regulator (resistor which asctually a PWM module) and the blower motor was all moot. Turned out that the problem was a burned power connector direcly to the right hand side of the passenger foot area under the carpet. There's another thread here describing this and his fix of cutting it out and directly soldering the positive power supply wire together to bypass the connector.
I would much rather replace the connector and pins and do it right.
Can someone help me with the part number of the connector and male and female pins for the power supply wire - it's 10or12awg wire for the hot power supply wire.
how hard is it to spin the fan by hand?
That increases the current that burns the harness you've found.
Lube the fan sleeve bearins to allow moderate current.
Did you double-check the state of the harness connector that is under the carpet? Because the blower pull too much current that conector tends to melt and create further resistance. Standard issue for the W166 platform, here is the documentation, and a video https://static.nhtsa.gov/odi/tsbs/20...36175-9999.pdf
The melted connector was exactly the problem. See attached photos.
Can't beleive this wasn't a safety recall. Could have easily caused a fire.
Just to share a tidbit of interesting information, that same harness if disconnected removes all power and function from the dash and the key identification system. I left it unplugged overnight to prevent anymore current from reaching the fan body. Came out to do a quick errand in the morning and the car was from all appearances dead. No way to start the motor, no way to lock or unlock doors through the key-fob, and no gauges on the dashboard. IF anyone else goes through this just be aware that all functionality goes dark until the connector is put back together.
As for the fix I pulled the pins for the fan power supply ( the heavy red wire) which was easy to identify as that's the one that was melted to the point it simply slipped out of the housing when touched. I then soldered the line back together with normal solder and used both a marine grade heat shrink butt connector (and solder joint). Then placed a couple of normal heat shrink tubes on top of the joint to ensure no potential abrasion damage as it sits next to the orginal coupler with relatively hard edges.
If anyone has has the part numbers for the male and female side of this couple and the crimp pins I would greatly appreciate it.
Just realized that JCM_MB left a service bulletin link that contains the part numbers inside the PDF document. Thank you very much for providing that. For anyone else looking for those part numbers I'll link that PDF here again. Look at the document for useful part numbers for the male, female and pins for the coupler. And don't forget yhou'll make your life easier with a Pin removal tool and a proper molex style crimping tool to properly roll over the wings of the pin onto the wire. I ordered one from amazon for about $16.
