Tail Light Issue

Gotta love that wiring . . .
Post Reply
davery
Posts: 806
Joined: Sun Apr 15, 2012 8:51 pm
Your car is a: 1985 Spider
Location: Ohio

Tail Light Issue

Post by davery »

My passenger side tail light, rear side light and license plate lights are not working. All the driver's side lights work, as well as the brake and turn lights on the passenger side. I'm thinking maybe it's a ground somewhere? I need to mention I replaced the license plate lights with a couple of LED bolt lights. I used the existing wires from the license plate lights and just spliced in the wiring from the LED's. They worked for several months, but could this be an issue?
Last edited by davery on Sat Sep 07, 2013 10:36 pm, edited 1 time in total.
Don Avery
Dayton, OH/Sarasota,FL
1985 Pininfarina
2011 Eos
2012 Mercedes E550 Cabriolet
User avatar
azruss
Posts: 3659
Joined: Sun May 30, 2010 12:24 pm
Your car is a: 80 Fiat 2000 FI

Re: Tail LIght Issue

Post by azruss »

I would look at the circuit board. I found i has very poor + and ground connections between the socket and the board. You can test by running a jumper from each socket to the corresponding circuit on the board or to ground.
davery
Posts: 806
Joined: Sun Apr 15, 2012 8:51 pm
Your car is a: 1985 Spider
Location: Ohio

Re: Tail Light Issue

Post by davery »

azruss wrote:I would look at the circuit board. I found i has very poor + and ground connections between the socket and the board. You can test by running a jumper from each socket to the corresponding circuit on the board or to ground.
Does the ground for the passenger side rear side light and both license plates light go through the socket for the passenger side tail light?
Don Avery
Dayton, OH/Sarasota,FL
1985 Pininfarina
2011 Eos
2012 Mercedes E550 Cabriolet
User avatar
azruss
Posts: 3659
Joined: Sun May 30, 2010 12:24 pm
Your car is a: 80 Fiat 2000 FI

Re: Tail Light Issue

Post by azruss »

the main ground for all the rear lights is the one attached to the left side tail light bolt down stud. I found this to be a very ineffective ground and i moved mine to one of the fasteners on the gas filler bucket. The ground runs thru both circuit boards and connecting harness. what i found with mine was the socket itself wasnt making good contact with the circuit board on either the ground circuit or the hot circuit. this is why some bulbs are fine and others are not.
davery
Posts: 806
Joined: Sun Apr 15, 2012 8:51 pm
Your car is a: 1985 Spider
Location: Ohio

Re: Tail Light Issue

Post by davery »

So an interesting thing just happened. I had to run a separate ground for the LED's, since the OEM license plate lights used the light as a ground. I ran a line to the ground for the battery (my battery is under the passenger side rear fender) for the LED's. I was disconnecting that line and the LED's blinked on and off. I jiggled the wire and the LED's came on. Unfortunately, they should have not been on at all as there was no power to the rear lights. The ignition was off. Did I hook up the LED's incorrectly and fry something inside passenger side circuit panel? Or maybe the wiring harness going from the driver side to the passenger side light panels?
Don Avery
Dayton, OH/Sarasota,FL
1985 Pininfarina
2011 Eos
2012 Mercedes E550 Cabriolet
davery
Posts: 806
Joined: Sun Apr 15, 2012 8:51 pm
Your car is a: 1985 Spider
Location: Ohio

Re: Tail Light Issue

Post by davery »

Update - so I found three 8A fuses blown. I replaced those and both tail lights worked. When I had my wife press the brake pedal, the pass side brake light went on but the pass side tail light went off. It blew the fuse. The drivers side works fine. I assume I have a short somewhere, but where?
Don Avery
Dayton, OH/Sarasota,FL
1985 Pininfarina
2011 Eos
2012 Mercedes E550 Cabriolet
davery
Posts: 806
Joined: Sun Apr 15, 2012 8:51 pm
Your car is a: 1985 Spider
Location: Ohio

Re: Tail Light Issue

Post by davery »

Update - so I found three 8A fuses blown. I replaced those and both tail lights worked. When I had my wife press the brake pedal, the pass side brake light went on but the pass side tail light went off. It blew the fuse. The drivers side works fine. I assume I have a short somewhere, but where?

I recently noticed the trunk light was just hanging. It has never worked, but I didn't really bother me. Is it possible there is a ground for this light that has come loose and caused my issues? Does anyone have a pic of the trunk light without the lens so I can see how it is hooked up?
Don Avery
Dayton, OH/Sarasota,FL
1985 Pininfarina
2011 Eos
2012 Mercedes E550 Cabriolet
User avatar
azruss
Posts: 3659
Joined: Sun May 30, 2010 12:24 pm
Your car is a: 80 Fiat 2000 FI

Re: Tail Light Issue

Post by azruss »

the trunk light should ground to the chassis by bolting it in position. should have nothing to do with any of your other issues as long as there is no exposed wire connection that is touching the body, shorting and blowing a fuse.
davery
Posts: 806
Joined: Sun Apr 15, 2012 8:51 pm
Your car is a: 1985 Spider
Location: Ohio

Re: Tail Light Issue

Post by davery »

azruss wrote:the trunk light should ground to the chassis by bolting it in position. should have nothing to do with any of your other issues as long as there is no exposed wire connection that is touching the body, shorting and blowing a fuse.
I have no idea how the trunk light is hooked up. I just a couple of wires attached to what appears to be an alum peice and it is just hanging.
Don Avery
Dayton, OH/Sarasota,FL
1985 Pininfarina
2011 Eos
2012 Mercedes E550 Cabriolet
Post Reply