gunbunny

We have a new-to-us 2012 E350, and the AC blower goes our intermittently. There's no real rhyme or reason. It will be on, we stop the car and turn off the motor, start the car, and it will stay off for a random period of time. When it's on, it's on until the car is shut off. When it's off, it's off until it decides to come back on.

Having trouble finding the fuse diagram. Looked online and only one of the diagrams (the under-hood) one seems to match our car. The fusebox in the right-rear of the trunk doesn't match the diagrams I've found so far. I also found AC reset instructions, but they were for an older E-Class.

Any suggestions on troubleshooting and diagnosis are appreciated.

mercy-me

Most likely not a fuse issue. If fuse were bad then motor would not run again after failure.
I had a similar problem with my car a few months back. I wound up changing out the regulator first since my problem was intermittent like yours but after a few days I was back to square one with fan motor running intermittenly. I then changed out the motor and have had no problems since. I do have SDS and initial scan did indicate a bad motor but again, I thought intermittent pointed to regulator.

Good luck,

Bob

GuestFromTampa

Most likely you need Blower Motor (BEHR Part Number: 351043101 / 351 043 101) and Blower Motor Resistor (BEHR Part Number: 351321491 / 351 321 491)

gunbunny

Thanks for the info! Looks like a far easier install than the AC blower from our '97 Seville. That took a turnbuckle around the motor to tilt it forward so there was room to get access to the fan.

joebog

Started having this problem with my 2012 ML350 several months ago. Had the local shop dig under the passenger seat and examine all the connectors. This was intermittent, and so I waited until not working and took to local shop, where they examined and reseated all the connectors under the front seat. No trouble found, but shortly after worked for a while again. The problem recurs every few weeks. The most reliable solution thus far, which I found buried in one of these fora, is to sit in the passenger seat while car is running and to stomp as hard as you can (like a kid having a tantrum) on the incline portion of the floor, In less than a minute of continuous stomping It has worked several times for me. I hesitate to take it to the dealer, dreading the cost of finding this obvious short BTW, if my wife stomps on the floor, she is unsuccessful.

juanmor40

You may want to take a look at this video, and see "the inclined part of the passenger" footwell. It is not rocket science to remove it and look under the metal shield.

There are 2 or 3 points for grounds in there, you want them CLEAN and TIGHT. No loose connections. Also, at the end of the video notice wiring near the metal cover. Check yours and verify the metal is not pulling on the wiring, or that some wire is already cut.

Have anyone worked in that area of your vehicle before? Perhaps something was not put back together correctly?

jjpaget

I'm having the same issue. I recently replaced the fan (3 months ago). The blower started running only on low last week. Forums said it was likely the resistor. So, I replaced the resistor. Once the resistor was replaced, the fan started running intermittently. It will blow for 30 seconds and then stop for 2. After the two seconds of downtime, it starts again only to continue the cycle for about 8-10 minutes. After that, it will stop and not restart until the vehicle is started again. I got a replacement resistor and the results are the same.

Does anyone have any ideas?

juanmor40

On the W166 platform, ML, an issue with similar symptoms is due to damaged connector in the wiring towards the blower -> voltage drop/contact resistance in the wiring.

Trace the wiring bacwards from the blower ?