Intermittent Blower on 2012 ML350
#1
Intermittent Blower on 2012 ML350
The other day my 2012 ML350 blower motor intermittently would not come on when selected from the climate controls. After researching this online some people have had problems with the drain hole becoming plugged and causing water to get into the motor and resistor board, but when I pulled my motor it was clean and had no water damage. I can connect 12v to the motor and it works normally when not in the vehicle. Doing further testing I have found that when the motor does not come on I have 3.9v on the input side of the resistor pack and zero volts on the output to the fan motor. When the motor works the input side on the resistor pack is 12v and the output to the motor is also 12v+/- depending on the blower speed selected. I have checked the continuity to the fuse block and all of the connectors at the resistor pack and motor and everything seems correct. Is their a relay under the back seat or under the hood that controls the voltage to the blower assembly or to the climate control system? When the blower is not working functions on the climate control seem normal except that the max cool, max defrost and the fan functions do not work to change the blower speed but the led displays change as if the climate control module is telling the blower to change speeds. Is there a reset procedure or diagnostics that can check the climate control system without a visit to the dealer?
I contacted my local dealer and they said that without connecting the vehicle up to the STAR diagnostic system to see if it has a code for a problem then they could not even give me an idea about the cost to repair the problem.
If anybody has had this problem or has any ideas to check that would be a big help.
Thanks
I contacted my local dealer and they said that without connecting the vehicle up to the STAR diagnostic system to see if it has a code for a problem then they could not even give me an idea about the cost to repair the problem.
If anybody has had this problem or has any ideas to check that would be a big help.
Thanks
#2
Member
I'm having this problem too over the last month. Thought it was fixed but today after going through a car wash I lost blower again. That makes me think that there is something to what you are saying about drain tube getting blocked -- does anyone have more info about such drain tubes and where they are?
I don't want to keep blowing up regulators and/or motors.
First time this happened I ordered a blower and regulator from a wrecking yard. I only installed the regulator because I figured that was the problem. I worked for maybe 1 or 2 trips in the car then it died.
Second repair attempt, I ordered a brand new regulator and installed that along with the blower that I hadn't used from the wrecking yard. The only thing I could think of going wrong on the first attempt was that maybe a bad blower motor caused the first and second regulators to go bad. I can confirm that the voltages were as described by the OP above when system was good/bad.
Above repair lasted a couple of weeks and today, a few hours after going through a car wash, I started up the car and NO BLOWER again. I want to pull my hair out!
This is happening in a GL350 but the blower and regulator are exactly the same in the X166 as W166. The used parts above came out of an ML, not a GL.
I'm thinking about just ordering another used blower and regulator from a wrecking yard because I can get that for $75 shipped. Then hope that these parts last a little while again and that if/when they go bad I can get some additional clues as to what may be causing this (such as if it happens after rain or a car wash etc).
The other option would be to go to the stealership and see if they can diagnose the root cause of this. This feels like a "ghost" in the system so it may get very expensive very fast at the dealer.... especially if they want to supply a new blower ($350 dealer price) and regulator ($350).
I don't want to keep blowing up regulators and/or motors.
First time this happened I ordered a blower and regulator from a wrecking yard. I only installed the regulator because I figured that was the problem. I worked for maybe 1 or 2 trips in the car then it died.
Second repair attempt, I ordered a brand new regulator and installed that along with the blower that I hadn't used from the wrecking yard. The only thing I could think of going wrong on the first attempt was that maybe a bad blower motor caused the first and second regulators to go bad. I can confirm that the voltages were as described by the OP above when system was good/bad.
Above repair lasted a couple of weeks and today, a few hours after going through a car wash, I started up the car and NO BLOWER again. I want to pull my hair out!
This is happening in a GL350 but the blower and regulator are exactly the same in the X166 as W166. The used parts above came out of an ML, not a GL.
I'm thinking about just ordering another used blower and regulator from a wrecking yard because I can get that for $75 shipped. Then hope that these parts last a little while again and that if/when they go bad I can get some additional clues as to what may be causing this (such as if it happens after rain or a car wash etc).
The other option would be to go to the stealership and see if they can diagnose the root cause of this. This feels like a "ghost" in the system so it may get very expensive very fast at the dealer.... especially if they want to supply a new blower ($350 dealer price) and regulator ($350).
#3
Sorry to bring back an old thread, but I have been chasing this exact problem. Replaced a couple regulators and a blower motor. Still intermittent functionality. Did you guys have any luck solving the problem?
#4
Member
Yes! I'm sorry that I didn't follow up earlier to save you some trouble. There is a connection that gets loose and starts to burn up from shorting out. There is a service bulletin about it. Let me see if I can find it fo post.
HVAC BLOWER MOTOR INOPERATIVE AND DTC 912F87.pdf
AIR CONDITIONING IS INOPERATIVE, FAULT CODE 91EB11 OR 91EB15 IS STORED.pdf
AC BLOWER INOPERATIVE DTC 912F87 IN ACC THE FRONT BLOWER REGULATOR HAS A MALFUNCTION.pdf
HVAC BLOWER MOTOR INOPERATIVE AND DTC 912F87.pdf
AIR CONDITIONING IS INOPERATIVE, FAULT CODE 91EB11 OR 91EB15 IS STORED.pdf
AC BLOWER INOPERATIVE DTC 912F87 IN ACC THE FRONT BLOWER REGULATOR HAS A MALFUNCTION.pdf
The following 5 users liked this post by CA_Tallguy:
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peter2772000 (05-01-2018)
#5
CA_Tallguy, you are a gentleman and a scholar. Thanks so much for taking the time to respond and for sharing the PDFs. I have the W166, but I thought it was behaving like a bad connection somewhere and bet it is that. I will dig into it soon and check back in with what I find out. Thanks again so much!
#6
Member
Note -- you might want to pickup a CarSoft scanner. These docs mention some fault codes so that might help you or someone else who comes across this trying to troubleshoot. But those codes are going to be deep and not available via a normal OBDII scanner. You need the Carsoft specific to mercedes or another specialized scanner.
#7
Yes! I'm sorry that I didn't follow up earlier to save you some trouble. There is a connection that gets loose and starts to burn up from shorting out. There is a service bulletin about it. Let me see if I can find it fo post.
Attachment 416449
Attachment 416450
Attachment 416451
Attachment 416449
Attachment 416450
Attachment 416451
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ninaT86 (07-02-2022)
Trending Topics
#8
May have found the solution...
Hi All, I recently purchased a white 2012 ML 350 4MATIC and motor blower went out. I thought it was water related as well but when no water was found I said "prepare for the screwing" let's go to the dealership. $498 later and them claiming they had to remove the passenger front seat and carpet they replaced a "wiring harness". After that point no more issues. Fast forward three months and compliments of a deer and the wire barricade on I-40 in TN I totaled that ML 350. Never fear, I bought another one. :-) Guess what... Have had this (new to me) blue 2012 ML 350 4MATIC and it is starting to do the same thing. What you can do is open the passenger door and slam your foot down on the floor board while the blower is set to level 7 high. You will find the sweet spot and the blower will cut back on. Or go to the dealer and spend $498. I'm beating the passenger floor board for another couple of months though...
Hope this helps!
Pepper
#9
I’m still having the problem cause I won’t go to the dealer, but I’ve also problem down to a soft spot on the passenger side floor. I’ve got the panels off but trying to figure out how to get the carpet up. The spot is like 3 inches from the door, but doesn’t seem to be the connector that the service bulletin suggests. So thanks for your post confirming that my problem is the same. Amazing they haven’t done a recall on this!
#10
Hi All, I recently purchased a white 2012 ML 350 4MATIC and motor blower went out. I thought it was water related as well but when no water was found I said "prepare for the screwing" let's go to the dealership. $498 later and them claiming they had to remove the passenger front seat and carpet they replaced a "wiring harness". After that point no more issues. Fast forward three months and compliments of a deer and the wire barricade on I-40 in TN I totaled that ML 350. Never fear, I bought another one. :-) Guess what... Have had this (new to me) blue 2012 ML 350 4MATIC and it is starting to do the same thing. What you can do is open the passenger door and slam your foot down on the floor board while the blower is set to level 7 high. You will find the sweet spot and the blower will cut back on. Or go to the dealer and spend $498. I'm beating the passenger floor board for another couple of months though...
Hope this helps!
Pepper
Hope this helps!
Pepper
#11
I just purchase my 2012 ML350 two months ago. Today when I left the gym my heat would not blow from the vents. I drove to the maintenance shop and the guy was pretty rude, so I decided to Google and see if there was a simple fix. Your awesome, I rolled my eyes initially when I read your post. However, I decided what the heck do I have to loose. Sure enough one stomp on the passenger side floor and I had heat again. Thank you so much!!!
#12
Do you know what parts are needed for this repair? The dealership of course says they dont know what im talking about and want me to replace the whole harness. Also is there a diagram or video on how to remove the front seat and carpet?
#13
NOTE, if you do have to disconnect the wire under the seat, you’ll need to disable the airbag first. (I don’t know how to do this, my mechanic had to fix it afterward). Maybe google that if you have to. But again, try to avoid.
it’s unbelievable to me that Mercedes never recalled the vehicle over this. Good luck, if you have any more questions, I’ll help best I can.
#14
Member
I was able to do this repair on our 12 ML350. I didn't have to remove the seat. The problem lies where the floorboard (where your right foot would be) goes up into the dash. You just have to pull up hard on the carpet. You will notice one of the wires is burned. I cut the bad part of the one wire, and used a wire connector to reconnect the wire. It's been a couple of years since I did it, but it was not that hard. I also went through a new motor and new regulators to no avail. Mercedes did not have a heavy enough gauge wire to handle the current.
#15
Hi I’m in the Uk and have same issue
I was able to do this repair on our 12 ML350. I didn't have to remove the seat. The problem lies where the floorboard (where your right foot would be) goes up into the dash. You just have to pull up hard on the carpet. You will notice one of the wires is burned. I cut the bad part of the one wire, and used a wire connector to reconnect the wire. It's been a couple of years since I did it, but it was not that hard. I also went through a new motor and new regulators to no avail. Mercedes did not have a heavy enough gauge wire to handle the current.
easy just wondering where to start any help appreciated
#16
Member
I imagine that RHD cars are going to have the blower fan on the left hand side. If you have ever changed your cabin air filters, that will confirm which side your blower motor is on, and thus the wiring harness.
The covers should "pop" off. You will need to remove the under the dash plastic cover which is held in with 4 or 5 hex screws. GLWR
The covers should "pop" off. You will need to remove the under the dash plastic cover which is held in with 4 or 5 hex screws. GLWR
#17
Ml250 bluetec heaters
Hi Marcd cheers for the quick reply yes I know where the four screws are and the panel should drop down and pop pout hopefully I will have a go when I get a good few hours free and hopefully pop the panels off I’m presuming the left hand side small panel will pop out the the ones along the sill that meet the carpet do also . Would I be right in thinking that .
#18
Member
Yes. Pull back the door insulation and carefully pry the side kick panel out of place. Trace the power wiring from the fan down into the footwell and you should see the compromised portion of the wire somewhere between the footwell angles up into the firewall area. You don't have much "play"/slack in the wiring so be careful not to cut too much out, unless you want to place additional "patch" cable in place.
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Scargo (09-05-2021)
#19
Member
I did find a good post on this forum or another forum where someone posted photos of his repair. It's been a while, so I haven't researched it.
#20
Member
Ah, now I remember! I ended up taking either the negative or line wire and pin out of both of the connectors because it had shorted/melted, You should see where it's charred. Then bypassed the connector of the wire of the bad pin and just spliced it direct. So in other words, take the bad wire out of both ends of the connector and direct connect them. I think the issue was the pin was too small to manage the current going through it.
The following users liked this post:
steveyfly (04-29-2021)
#21
Hi marcd heaters
Yes. Pull back the door insulation and carefully pry the side kick panel out of place. Trace the power wiring from the fan down into the footwell and you should see the compromised portion of the wire somewhere between the footwell angles up into the firewall area. You don't have much "play"/slack in the wiring so be careful not to cut too much out, unless you want to place additional "patch" cable in place.
#22
Thanks
Yes! I'm sorry that I didn't follow up earlier to save you some trouble. There is a connection that gets loose and starts to burn up from shorting out. There is a service bulletin about it. Let me see if I can find it fo post.
Attachment 416449
Attachment 416450
Attachment 416451
Attachment 416449
Attachment 416450
Attachment 416451
I just got my ML home, buying it second hand and the fan stopped..
good to have you guys, THANKS !!!
#23
Newbie
Join Date: Aug 2017
Location: USA, CA
Posts: 4
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2012 ML350 BlueTec
As it happened to my 2012 ML (Error: 912F87 in AC system), thanks to this thread and all tips posted, I've hoped to fix it without braking the budget.
So, after hitting the passenger side floor and blower started working for some time, I decided to take further actions to fix it permanently - see attached.
- Do not disconnect wires from the seat but just remove 4 bolts and tilt it back;
- Fixed by puling both ends of problematic wire from connectors and connecting it using "Wago 221-412 Lever-Nuts 2 Conductor Compact Connectors";
- Locate/place fixed connection higher at the side but not under the carpet to monitor it and fix it again if needed without removing all the staff but plastic side panel only. The length of wire should allow it.
So, after hitting the passenger side floor and blower started working for some time, I decided to take further actions to fix it permanently - see attached.
- Do not disconnect wires from the seat but just remove 4 bolts and tilt it back;
- Fixed by puling both ends of problematic wire from connectors and connecting it using "Wago 221-412 Lever-Nuts 2 Conductor Compact Connectors";
- Locate/place fixed connection higher at the side but not under the carpet to monitor it and fix it again if needed without removing all the staff but plastic side panel only. The length of wire should allow it.
Last edited by Oleg Olekshii; 09-02-2021 at 01:06 PM.
#24
Bad wiring easy fix!!!
Hi All, I recently purchased a white 2012 ML 350 4MATIC and motor blower went out. I thought it was water related as well but when no water was found I said "prepare for the screwing" let's go to the dealership. $498 later and them claiming they had to remove the passenger front seat and carpet they replaced a "wiring harness". After that point no more issues. Fast forward three months and compliments of a deer and the wire barricade on I-40 in TN I totaled that ML 350. Never fear, I bought another one. :-) Guess what... Have had this (new to me) blue 2012 ML 350 4MATIC and it is starting to do the same thing. What you can do is open the passenger door and slam your foot down on the floor board while the blower is set to level 7 high. You will find the sweet spot and the blower will cut back on. Or go to the dealer and spend $498. I'm beating the passenger floor board for another couple of months though...
Hope this helps!
Pepper
Hope this helps!
Pepper
#25
Any pictures of removing the carpet?
Hi All, I recently purchased a white 2012 ML 350 4MATIC and motor blower went out. I thought it was water related as well but when no water was found I said "prepare for the screwing" let's go to the dealership. $498 later and them claiming they had to remove the passenger front seat and carpet they replaced a "wiring harness". After that point no more issues. Fast forward three months and compliments of a deer and the wire barricade on I-40 in TN I totaled that ML 350. Never fear, I bought another one. :-) Guess what... Have had this (new to me) blue 2012 ML 350 4MATIC and it is starting to do the same thing. What you can do is open the passenger door and slam your foot down on the floor board while the blower is set to level 7 high. You will find the sweet spot and the blower will cut back on. Or go to the dealer and spend $498. I'm beating the passenger floor board for another couple of months though...
Hope this helps!
Pepper
Hope this helps!
Pepper
I have this exact issue, and pounding my foot has worked, but is not as effective after several times, so I want to just fix it... any other pics of the carpet removal? I though of just cutting it, but not sure exactly where the wires are located...
thanks!