Backup Lights not working..

[ScottyP]

Ive been trying to get my backup lights working on my 95 C280 auto.
Replaced the backup bulbs with new ones and replaced the Lockout switch. Still No Backup Lights.

So I decided to test the wiring..

Test between the 24pin connection under the Hood and the Neutral Safety (lockout) Switch under the car:
1. Unplugged both the 24pin connector and the lockout switch
2. Tested for continuity between the top portion of the 16pin connector Pin 5 to Pin 1 on the switch connector - PASSED
3. Tested for continuity between the top portion of the 16pin connector Pin 6 to Pin 2 on the connector at the switch PASSED
4. Reconnected the Lockout Switch.

Test between the 24pin connector AND the wiring connection in the passenger side kick panel AND to the Backup Lights:

1. Removed the passenger side kick panel. Searched for the connection with the 2 gray/yellow wires coming from the engine compartment and a single wire going to the backup lights - FOUND IT
2. Disconnected the connection and tested the top portion of the connector with the 2 gray/yellow wires from the engine compartment.
3. Tested for continuity between Pin 6 on the bottom portion of the 16pin connector to the double gray/yellow plug at the kick panel - PASSED
4. Tested for continuity between Pin 6 on the bottom portion of the 16pin connector TO the double gray/yellow plug at the kick panel - PASSED
5. Removed the drivers side tail light and remove the connector. Within the connector, found Pin 4 with the gray/yellow wire.
6. Tested for continuity between the bottom section of the kick panel plug (with single gray/yellow wire) and the driver tail light plug - Pin 4 - PASSED
7. Removed the Passenger Tail lamp and performed the same test using the tail light plug - Pin 4 - PASSED
8. Tested between Driver tail lamp and Passenger tail lamp using Pin 4 on both - PASSED
9. Tested between each tail lamp plugs and Pin 6 at the 16pin connector under the hood duhhhh.... - Both PASSED
10. Reconnected the both tail lamp connections and put the tail lamps back together. Plugged up the connector at the passenger kick panel and put it back together.

Now, the wiring all checked out and everything tested good. I have a new switch installed. Why are my backup lights not working? :(

Investigation remaining....
Where are the two gray/yellow wires coming from at the Kick panel?
One is the 16pin connector under the hood; where does the other one originate?
Forgot to do the test again between the pin 5 & pin 6 at the 16pin connector for 12v with the car running and in reverse.
Maybe the new switch requires adjusting?

Does the backup lights come thru the light control unit above the fuse box?

Anyone has any ideas for me to try.. Need to get these lights working before I get in an accident while backing..
Thanks

[714guy]

I have the same problem, but my light will work if i move it in the spot (i have to find it). the mechanic told me it was a neutral swtich or somthing in the tranny and it was pretty pricey. I haven't changed it yet though.

Let me know what you find out with your problem.

GOOD LUCK!!

[ScottyP]

I will Post whats causing my problem 714guy when I figure this out. But your problem can be fixed by adjusting the neutral switch. Turn the ignition switch to the ON position. Put the car in reverse (with the emergency brakes on), loosen the 2 screws and slowly adjust the left side of the neutral switch until the backup lights comes on. Then carefully tighten the right side screw to hold the new setting and finally tighten the left side. Your lights will then work correctly.


Anyone know where the two wires coming into the kick panel originates? I really need a diagram of this wiring.

[jnenad16]

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nenad

[ScottyP]

Originally posted by jnenad16
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nenad

I finally found it. It was the flaky german wires... :(
After testing for 12 volts at the switch on Pin #1, I decided to tear out the wiring and check it. The whole wiring bundle between the 24pin connector and the switch (all 8 wire) were cracked up. As I untaped the wiring, the german wiring was crumbling in my hands... :(
Decided to rewire the entire bundle with new american wiring.

Spent the evening yesterday removing the bundle, then changing the wiring. Then, today I installed the new bundle reconnecting the 24pin connections, the starter wire, 2 wires to the transmission and a wire to the rear of the tranny. It was a dirty job but I got it done today...

Now, my backup lights work and it could be my imagination but the car appears more peppy. Finally, done with lights. :D

Now on to the radio. I will probably just start by buying a new head unit and some speakers, then rewire the entire system (removing the factory stuff). Its less fustrating than messing with the german fragile wiring.

Scotty

[ScottyP]

Thanks everyone for your help and assistance. And I really thank strictlyspeakin for the wiring color/mapping info (without this info I would have been completely lost). Hopefully, this thread will help someone in the future with backup lights problems. TEST THE WIRING with an ohm meter to determine if the wires are good. This Wire Bundle is especially exposed to the elements under the car: heat from the engine, and road water/snow. Due to the biodegradeable materials used for the wire cover/wrapping made in Germany, it will crackup in all directions & deteriorate inside of the bundle causing electrical shorts & breakage.

Thanks again to all..

[94benZo]

scotty,
you have picture where you found these bundle of connectors? I am having the same problem and my mechanic can't figure it out. If I can tell them where to look, it'll be fantastic...
thanks

[ScottyP]

Its the bundle from the 24pin connector under the hood (beside the ABS unit) to the lockout switch. At the 24pin connection end, the bundle has 6 wires: 1 large black wire to the rear of the tranny, 1 large brown wire to the side of the tranny, 2 small wires to the starter, and 2 small wires to the lockout switch (All wires were cracked except the black wire in my harness). At the lockout switch connection end, the bundle has 8 wires: 2 extra large wires come in the bundle under the starter, 4 wires from the switch connector, 1 black wire from the back of the tranny, and 1 Brown wire from side of the tranny (all but the black wire were cracked at this end inside of my harness).

Open the top portion of the 24pin connector and you will find two (2) bundles. The one with 6 wires is the one that you want. You will see the wires and their condition at that end.

At the switch end, remove the connector from the lockout switch. Then start removing the tape from the bundle going into the switch. You will see the wires and their condition. (Note: this is where my wires had crumbled and shorted out causing the #2 wire at the switch to be burned apart). Now on the face of the switch connector, pull out/apart the middle section using a small screwdriver to release the small clips at the ends. Inside you will see the wire connection terminals. Make sure all wires are connected and not touching. (Note: my #2 wire was not connected inside of the connector. So, I actually had two breaks in the #2 wire.

Soldering the new wires to the connector terminals is really strange. The metal terminals on the connectors does not accept solder really well (if at all). So inside of the connector, I cut the old wires about an inch from the terminal and stripped the wire cover. Then with the new wires, I put small heat shrinkable tubes onto the new wire, connected the new wire to the old stripped terminal wire and soldered the joint. Finally, I covered the soldered connection by sliding the shrinkable tube down over all exposed wires to protect the connection. I heated the shrinkable tube to seal it and to keep it locked in-place.

For the new #2 wire connection, I found a way to connect it to the connector terminal. The old wire was broken off at the top of the terminal, making a new wire to old wire solder connection impossible. So this is what I did: I stripped 1/4" of the end of new wire and held it on the side of the #2 terminal . I then wrapped the terminal and the new wire with real fine (thin) solid copper wire (puchased at a local hobby shop). Now that the new wire connection was now held in-place, I could soldered across all of the copper wires and the top of terminal to complete the fix. To protect the connection, I used a slightly larger shrinkable tube to cover the connection. I also stuffed a small piece of scrap rubber between the #1 & #2 terminals as extra insurance to prevent the #2 wire from moving. Not professional, but it works.

The rewiring is NOT hard, just time consuming and dirty under the car. You must notice the connections under the starter and to the tranny from the harness. AND replace all suspect wires. Plan to spend some time under the car during removal and installation of the new wire. I rewrapped the bundle using the old type of electrical tape called "electrical friction tape" purchased at Home Depot.

Your Mercedes Biodegradable wires will deterioate inside of the bundle wrapping as well as the exposed wires leaving the bundle to their destination.. Dont be fooled into thinking that the bundle wrapping is protecting the wires from this breakdown process. It is happening and you must check the wires inside of the bundle wrapping for potential damage. Otherwise, you will be repeating the repairs again soon! Just ask me how I know... ;)

Good Luck!! Scotty

[ScottyP]

This is the unwrapped bundle at the 24pin connector under the hood. Note the cracked wires. The cracks run down the length of the wire as well as around the wire. BIO-DEGRADING!!!!

http://www.sr20forum.com/gallery/data/817/thumbs/DSC03037.JPG

Closeup of the 24pin bundle:
http://www.sr20forum.com/gallery/data/817/thumbs/DSC03036.JPG

Picture of the wires from the lockout switch end of the bundle. Note: The purple wire enters & exits the bundle under the starter and it was completely exposed as shown here!! BIO-DEGONE!!

Also note the 2 bottom wires are from inside of the switch connector. They were both burned and the #2 wire was loose inside of the connector.

http://www.sr20forum.com/gallery/data/817/thumbs/DSC03035.JPG

Mercedes should be forced to RECALL this wiring.. Its a Mercedes for petes sake!!! Where's the better engineering in this stuff?