ML270 W163 Battery Drain

henri_w_v

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W163/2002/ML270
My 2002 ML270's battery drains within a day. The battery has been tested to be good and is also reasonably new.

I think I have isolated it to the culprit. When I switch of the car I can still hear a motor running inside the cabin in the dash. I then did the battery draw test which was running at 600mA when the car is locked up. When I remove the internal fuse F5 related to instrument cluster and aircon the draw test drops down to 30mA.

So I am assuming it is an aircon flap or air blend motor not stopping since I read they have direct supply from the battery?

Can anyone tell me what is the best step to determine which motor it is before I rip the dash apart? How many different flap or airblend motors do the w163 cars have? I live in NZ and parts are ridiculously expensive so I buy them from overseas. I am hoping I can find the fault instead of having to take the dash apart then order the part to wait 2 weeks and have to take it apart again.

Most people complain about a clicking noise which I do not have, the gear must be completely stripped. I did try and reset the aircon with no luck. There is no air coming from the system when the car is off.

Thank you
 

television

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I somehow do not think that the actual motor is the reason, it is the control to that motor where I would look.
 
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henri_w_v

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Hi Television. Where would this be located? Does it have a specific name or is it the AAM?
 

television

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I do not know the ML that well re the electrics, Thinking again on the problem I wonder if that motor does have a problem in that it lost its memory, against that I always thought the there was no voltage on these motors when turned off. On many cars there is the CAN bus, if the CAN is not sleeping, then this could cause the motor to run, pulling the fuse might stop the drain, but the motor may not be the reason.

For example in my SL, the fan in the heater air sensing circuit was running all the time, sure I could pull the fuse and fan did not run, the actual fault was with the keyless go ECU that was keeping the CAN awake.
 
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henri_w_v

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W163/2002/ML270
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Footwell flap stepper linkage fail

So i found the cause of the constant motor noise after ignition has been switched off and the largest culprit of battery drain. It is the driver side ac footwell flap stepper motor and linkage.

The linkage arm connection to the stepper has a split in it. Not sure if the stepper motor was too strong and caused the linkage to fail because of a faulty stepper. Or was the link too weak and since the stepper could continue turning not finding the limit.

How do these steppers know when to stop? Are they limit sensing?

Does anyone have the part numbers for the linkage kit?

Thanks
 

jibcl500

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Just a guess but remove the heater control panel. then run test with this unit plugged.



jib
 

television

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Stepping motors are what we call digi proportional, they have turn counters built in, if the turn counts get lost or confused they might no stop or be out of range, on STAR they can be re set.
 

television

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With the control unplugged, the motor should stop as is not being told to go somewhere.
 
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