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7 Series - E38 (1995 - 2001)

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Old 02-03-2013, 06:34 PM
rrtec's Avatar
rrtec rrtec is offline
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Location: TN 37174
 
Join Date: Sep 2008
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Mein Auto: 540i/6 4/99
DIY- E38 Transmission Neutral Switch/ Gear Selector Switch- aka Harness rebuild...

Below you will find a solution to an issue I ran into this last week after a deep detail.

Symptoms: After a deep undercarriage clean/detail my car developed an issue where the dash cluster did not display the gear the car was in. When the display dissapeared the car had no idea what gear it was in. When the car was dry no issue at all, but after a car wash or a rain it would randomly act up..

Research: I did quite a bit of internet searching and all signs pointed to the neutral safety switch, stories of switches filled with water, etc prompted me to remove the switch and attempt to clean it out. On a sidebar the research also told me to check where the drain tube was clipped to the wires as this can cause a short over time...

Basic semi complete DIY Begins here.. Learn from my mistakes.. But at your own risk..

Time taken: about 2 hrs with switch "rebuild"

People Needed: 1-2

The neutral safety switch/gear selector switch is located on the drivers side of the transmission. With the car up on jack stands (be safe dummy) you can see the switch if you follow the harness that is clipped to the transmission..

There are only a few bolts to remove, so all you really need is a 10mm, 13mm, flat head screw driver and as you will hear... a prybar.. I used ratcheting wrenches they work wonders...

I started off by removing the gear selector cable, it comes off with the flathead screwdriver just slide the retaining clip down and set it to the side. There is a bolt at the end of the cable that will only need to be loosened to remove the cable. Just slide it toward the back of the car and out. Just let it hang. WHo cares..

Your next move will be to remove the armature for the selector cable. It is a 13mm nut. Comes off easy and dont loose it. Set the armature to the side. At this juncture I disconnected the harness from the connector and from the edge of the pan.

Now you will see there are two 10mm bolt heads, one at the front one at the rear. Undo them. set them to the side..

Here is where I wish I had looked at it a little closer because I was nervous putting it back together.. Before you gently pull and pry the swtich off try and see if there is a good alignment mark that you can reference when re-installing. Some threads said that the transmission had to be removed, some threads mention removing the heat shields.. I did none of these things. I wedged a pry bar beside the tranny/tunnel and had a helper pull the trans toward the passenger side of the car. the switch needed a little tweaking to remove (gently wiggled it, that didnt work, so I got a little more aggressive with a screw driver and started working it off without cracking the plastic cover.) The helper pryed the transmission over about 1 inch and i dropped the switch down...

Here is where the story gets sad.....

I bring the switch in and drill out the rivets on the back, inspect the harness and the switch and the harness attached to the switch. I opened my switch and imagine this.. PERFECT INSIDE!! GREAT!! I did all that work for nothing.. Dry as a bone, and no corrosion. All that crap and no futher to a solution. SO, I re-sealed the switch and riveted it back together with new rivets. Now what?

I inspected the harness attached to the switch and everything looked good, including the point where the drain line clips to the switch harness.. No damage. So I decided to get under there for another look around and try to figure out where my problem was. I was not ready to accept the fact that my transmission was going bad and only on wet days... SO I crawled around and looked for other harness issues. Low and Behold I found some slices in the harness (body side) I started pulling at the tiny cuts in the shielding and water came out of the harness after futher inspection I noticed that there were a few wires that had been knicked by whatever sliced the shielding and they were most likely shorting out while wet.

That is not an easy place to fix a harness so I had to come up with a plan to treat the wet harness and stop corrosion, seal it, and all this without removing the body harness or hacking it up.. So I bought and used the following items:

1) Contact cleaner- sprayed the harness down to get rid of the water
2) Battery terminal corrosion spray- used to seal the exposed wires from corrosion
3) Liquid electrical tape- Painted the harness/exposed areas liberally for waterproofing
4) Cold shrink tape- Wound this tightly over the repair, up and down a few times then re-painted with the liquid tape.

I put the switch back on with no indicating marks as to allignment (woops), connected the armature and nervously put the car through the gears to indicate that everything was connected correctly.

Sucess! The car selected the appropriate gears so I decided to drop it down and take it for a spin. Seemed to do great. I got everything good and wet and so far so good. Hopefully that was my only issue. Hope this helps someone. If you couldnt tell the switch removal was not needed, so my word of caution is to check the harness FIRSt!! EVEN THE BODY HARNESS!! Looked like some road debris had been thrown up at some time and sliced the harness a little... over time water would get in and short out the harness..
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Last edited by rrtec; 02-03-2013 at 06:51 PM.
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