Anyone with extensive experience with electrical issues?

Posted on 2012-04-06
Last Modified: 2012-08-13
Unusual electrical event today - key - door - window motor.


I already have a question about my power window, and some of those who commented referred to non electrical issues as a possibility

I now have evidence of electrical problems, so maybe some of you are good at automotive electrical and this question is electrical in nature.

Yesterday, I wiggled the wiring that extends between the door frame and frame of the car. I inspected a metal rod that appears to raise and lower the window. Nothing was observed. I cut a piece of heavy plastic to put over the window in case of rain.

What happened today is a mystery.
I unlocked the front door, got into the car and closed the door. When I inserted my "key" into the ignition, I hear a loud noise.
What the ----?
It was the rear window motor.
I pulled the key out of the ignition and the noise did not stop. I opened the driver door and the noise stopped.
I closed the door and inserted the key and the noise began again.
I tried to start the car and my battery is not charged enough to start the car, but it must have enough juice left, to power the window motor.

So, it looked like, the noise from the motor was not going to stop with the door closed. I unplugged the window motor. Then I got back in the car and left the driver side door open. Key out of the ignition. I then plugged the motor back in and no noise. I closed the front door and put the key in the ignition and the window motor runs. Pull the key out, and it runs, until I open the driver door.

So, I have unplugged the window motor.
This noise is not the same click, click, I got when I used the power window switch to try to raise or lower the window.

The noise today is clearly the motor running, not some clicking.

So, would the clicking be from the regulator?

And how to explain the left front door and ignition key being able to run the window motor?

It must have run the battery down, over night.
Question by:nickg5
  • 3
LVL 83

Accepted Solution

Dave Baldwin earned 300 total points
ID: 37817537
My ex bought an old Mercedes from a supposed Mercedes mechanic.  We had all sorts of little electrical problems until the day that she discovered that the battery connection to the starter motor wasn't very tight, just finger tight.  It turned out that all other electrical connections in the car came from that terminal thru another wire.  And since the connection was not tight, the two were not making good electrical contact.  After we tightened those connections on that terminal, everything else 'suddenly' started working correctly.

One of the oddities is that a lifted ground connection in particular can cause current to take a path that wasn't intended thru another device or possibly motor.  Check your connections everywhere in the car.  All of them that you can find.  Pull them apart and plug them back in.  If they are screw terminals, make sure they are clean, unscrew them a little and tighten them back down.  For safety, you might want to disconnect the battery while you're doing that.
LVL 15

Assisted Solution

Perarduaadastra earned 200 total points
ID: 37817692
I've seen this kind of problem a few times, and, regardless of the vehicle make and model, it usually has the same root cause: that scourge of the automotive industry (and most other industries as well, I suspect) known as shareholder design. This is a modus operandi that basically forces production costs to the lowest level possible, in order to maximise shareholder ROI, with inevitable adverse effects on reliability and ease of repair.

In this particular case, it's a dollar to a doughnut that the problem lies in the wiring harness between the bodyshell and the door. What happens is this: as the door opens and closes in normal service the harness bends backwards and forwards in the shut, and the insulation of the wires inside it eventually cracks and breaks (followed by the copper itself), causing shorts and open circuits that in turn produce some very odd symptoms, and which can ultimately destroy control units and/or cause wiring fires.
These problems are exacerbated by the large numbers of wires that are often present in these looms (to cope with all the bells-and-whistles functions so beloved of the sales force), and by cold weather, as the wiring insulation becomes stiffer and more brittle at low temperatures.
If I'm right (and I'm perfectly willing to accept that I may not be) then you might discover that there is a handy multi-plug connecting the door harness to the main loom of the car. Your initial joy at this thoughtfulness on the part of the vehicle manufacturer may unfortunately be somewhat tempered by the realisation that the plug is set into the door rather than the A- or B-post of the car, meaning that the broken section is actually part of the main wiring loom of the car...

In which case, it's a lot of awkward and tedious work with a soldering iron and heat-shrink sleeving to effect repairs. Using crimp or screw type connectors is normally a non-starter as there isn't usually room in the shut for them all to fit.
If you're very attached to the vehicle it is possible to get synthetic rubber-insulated braided-core wire that is specifically intended for use in environments where considerable movement is unavoidable, but it's still a lot of awkward and tedious work with a soldering iron and heat-shrink sleeving!

Keep in mind too that the driver's door is the usually the first to go, but that the others are probably silently plotting mischief as well, though this only applies if all the door harnesses have the same design - not all do, as I discovered on one car I had where it was the rear door wiring that broke because that harness had its exit points in the car and the door at the same height, forcing it to bend through about 45 degrees every time the door opened and closed. The front doors, on the other hand, had their A-post exit point about seven inches above that of the door, so that this length of harness was available to absorb the angular motion of the door, resulting in no problems at the front.

I hope that this helps you out a bit.
LVL 25

Author Comment

ID: 37848511
Here is the photo of the bad part. It will lower the window but won't raise it.

Rear window switch.

tThe front main switch controls the back window to.
The part was $8.00 and gas to drive the 5 miles to the U-Pull-It yard.
Professional not needed.
LVL 25

Author Comment

ID: 37848512
LVL 25

Author Closing Comment

ID: 37848514

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