Electrical Issue - Rear Lights

Robbie

Well-known member
Apr 20, 2004
1,463
1
NOVA
Ok, so I have been trying to trace down an electrical issue in my truck for a little bit now and have finally decided this needs to be taken care of properly. My rear tail-light, left side/driver side is out. The brake light works and the blinker works. But the rear tail light and running light do not. When I jumper hot wire to the line, I can get them to light up, so I know it's not the bulbs. I do not appear to be getting any voltage to power. I have checked and tested all fuses and all are good. I ran continuity test through the lines (battery disconnected) and I am good.

At this point I need to trace the wires into the dash and see what's going on. I am trying to determine which relays to check and also if this could be a switch issue. Any ideas on relays and if the switch could be an issue? The passenger rear lights come on no problem, as do both headlights.

The one thing that does pop up that might give hints as to issue - my blinkers work fine when lights are off. But when I turn lights on with blinkers running, the passenger/right side rear blinker and rear tail lamps blink opposite of each other - marker blink...tail light blink...marker blink...tail light blink. I think that usually indicates bad ground, but I have checked the rear grounds and they are good.

If anyone has any ideas, please speak up and I can try to answer questions. This is driving me crazy. This is a '95 Disco.
 
Last edited:

d1driver

Well-known member
Oct 19, 2005
3,153
1
Pittsburgh, PA
If you have a trailer wiring harness, try taking it out of the loop. It is inside the panel below the passenger side rear lights.
 

Recon

Member
Sep 16, 2010
6
0
Atlanta, Georgia
I find it strange that I'm having almost the exact same problem. My blinkers aren't going as crazy but driver side blinker is not activating. I had thought I fixed the problem by routing the jumper a little differently but there is still a short somewhere. Maybe this could also be the source of some of the bumper cap fogs not working correctly?
 

thequickervicar

Well-known member
Aug 12, 2010
241
0
Lancaster, PA
I had a mysterious rear light issue as well. I ended up cleaning ALL of the contact points & added dielectric grease to ALL points. Cleared up all but one of my problem. I had to run a bead of solder at one contact where the bulb holder meets the light assembly. Perhaps yours is just trying to find the path of least resistance & a simple contact cleanup will take care of it? I hope so.
 

Robbie

Well-known member
Apr 20, 2004
1,463
1
NOVA
i would love if that were the issue, but I have cleaned up contacts and the fact that when I apply power to the lines, all the lights work. so i'm just not getting voltage along the line. my problem is finding at what point does it stop. i have a new light switch coming and some relays. guess i will start swapping things out and trying to troubleshoot in and under the dash.
 

Robbie

Well-known member
Apr 20, 2004
1,463
1
NOVA
passenger side rear marker light fixed. bad ground. but that had no effect on driver's side rear lights. still no juice back there. changed out light switch, no change. any idea which relays turn on rear lights?
 

Quentin

Well-known member
Mar 19, 2006
419
0
Cape Town, South Africa
I still think that it's not a relay issue. Just checked the Haynes Manual and cannot find a relay for those lights.
You are getting no power there at all?.........Zero, nada, nil??
Recheck continuity of the fuses.
Those globes draw 21W......If my maths is right, that needs 1,75 AMPS.
Now if there's a bad connection, you will be losing power inline and my suspicion is that there's not enough power to illuminate those bulbs.
Also recheck your ground. Take some flex and run it from your battery neg and test directly to the globe mounting neg
 

Robbie

Well-known member
Apr 20, 2004
1,463
1
NOVA
thanks, will do. at this point, doesn't look like power is in the line at all. i have checked all the way up to where line disappears into dash. when i apply power to the line, my lights do come on. i will recheck fuses and check and reconfirm all grounds again. even run a dedicated test ground like you mention. driving me nuts.
 

Quentin

Well-known member
Mar 19, 2006
419
0
Cape Town, South Africa
Electrical faults are a bitch. Just keep to a methodical fault finding sequence and you'll find it.
Swopout the fuse again. It should be around a 10A . I've had brand new ones that look perfect, end up being duds.
Have you checked for power on the actual fuse holder yet or are you still getting there?
Let us know how it goes
 

paxton

Well-known member
Nov 13, 2006
1,246
2
Huntsville, AL
Take the lenses out and look at how they ground. I'll bet you see the little metal tabs are corroded. On my D1 I just ordered replacement lenses, but I imagine you can just wirebrush all the crap off.

<edit> Nevermind. Read the replies. </edit>
 

latarheel

Well-known member
Oct 10, 2011
183
4
AZ
I was confident I woudl find a resolution at the end of this thread but alas. robbie, did you ever find the solution? I discovered tonight that I have the same problem so will start troubleshooting tomorrow. Lucas, Prince of Darkness strikes again!
 

Robbie

Well-known member
Apr 20, 2004
1,463
1
NOVA
nope, never found a solution. i am now running a jumper from the power for passenger side lights to the driver's side lights. it works and this will allow my sanity to come back. maybe someday i will try and hunt down the issue again.
 

Rover_Hokie

Well-known member
Jun 7, 2008
355
0
Roanoke Valley, VA
'01 D2, I now have a similar issue. No dash lights around the speedo/tach, but odometer and 3 amigos light up as well as the high beam indicator. No lights on the switches around the binnacle. I have low beam and high beam headlights and fogs. No passenger side marker/city lights front or rear, but I do have turn signals. Interesting as well is the transmission shifter lighting is on when I have my turn signal stalk/lever completely off, but in position 1 for marker lights/city lights and then position 2 for headlights the transmission shifter light and red indicator go out. Just started on the way home tonight, so will check contacts, but I may replace the signal light stalk as I have a spare and just replaced it with a used one for other issues and cleaned the one I removed. So will give that a try, since I have it fresh in my mind, and it is a 5 minute swap. I cleaned the one I removed last time and put it back in and tested so I could keep it for a spare. I probably need to add some dielectric grease on the stalk contacts, as I cleaned a lot of it off with the corrosion and burned places, and did not add any back when I reassembled.
 

Rover_Hokie

Well-known member
Jun 7, 2008
355
0
Roanoke Valley, VA
Well, I read a few more threads, and looks like it may be

1) One of my passenger side lights DRL (City lights) or one of the front or rear marker lights that is out or not making contact due to corrosion or buggered up light socket or damaged pigtail behind the light socket
2) Could just be a fuse
3) The glove box light could be shorting out if I do find a blown fuse and replacing it is just blows again. http://singingcamel.com/site/?cat=72

So I will check these out before replacing the stalk. Thanks for the good documented info in other threads.
http://www.discoweb.org/forums/2) t...le mess. http://singingcamel.com/site/?cat=72http://singingcamel.com/site/?cat=72