Wiring Experts Needed

[deshetlr]

I killed my Optima so while installing the replacement I checked for parasitic drain. Sure enough I was drawing 380ma with everything off. I started through the fuses and the draw ended when I got to the fuse responsible for the license plate lights, fog light switch illumination and head light switch illumination (#7 group #2).

When I pulled the license plate lights I found a jumper from the right taillight to the license plate light (it was working). I removed the jumper, the parasitic draw disappeared but the license plate lights quit working. I checked the headlight switch and foglight switch illumination and the foglight illumination works but the headlight illumination does not.

So where do I go from here? I cannot live with the parasitic draw or the lack of license plate illumination.

[deshetlr]

Well let's try this again.

[gregwils]

Scott,

I am not a wiring expert at all, but since I have a brother named Scott and I personally own an '86 Guards Red coupe, I felt compelled to respond. I also happen to have a scanned copy of the lighting diagram for our cars.

I would assume that someone installed a jumper wire for the license plate lights because the original wire was grounding and they either didn't take the time to find it or couldn't. I guess you have a few choices. You could try to fix the problem with the original wire. You could fix the jumper. Or, you could run a new jumper. The answer probably depends on your time, skills and how anal you are about stuff this.

Could you elaborate on the 'switch illumination'? Specifically, what are you referencing? Also, what was the source for the jumper wire?

Do you own an ohmmeter and a test light?

[deshetlr]

The jumper was coming from the right taillight. The headlight switch apparently should light up when pulled out (on). The circuit for that is on the same fuse as the license plate lights. I see it not working as a possible clue to the unwanted ground.

[deshetlr]

The jumper was coming from the right taillight. The headlight switch apparently should light up when pulled out (on). The circuit for that is on the same fuse as the license plate lights. I see it not working as a possible clue to the unwanted ground.

[deshetlr]

Yea I'm anal about this stuff but I am terrible with electric. I'm guessing the issue is in the run to the rear of the car. The whole front harness was removed this spring and professionally repaired due to a short after the light switch failed. The license plate light issue was way prior to that (PO put in the jumper) so I am assuming ther issue is aft of what was gone through. Does that logic hold up?

[gregwils]

I am going to take a guess at this, but if he jumped it improperly then it makes sense that it is always on. The brake lights would be an always on circuit. Do you know if it was jumped to the black/white wire? Or black/yellow or grey/red? I also wonder if the two additional license plate lights overload the circuit.

If you run a long wire from the license plate light hot wire back up to your fuse box, then you should be able to disconnect the grey wire from the fuse box to test for continuity. At least, that is how the drawings look to me.

Actually, if you haven't already. I would pull the clean all the connectors for the existing license plate light and clean. I would also pull the left and right tail light assemblies and clean the grounds really well. They are exposed to the dirt and debris kicked up by the rear tires. I would coat everything with dielectric grease. Finally, clean the license sockets and replace with the new correct specification (wattage). Then you can start the next steps.

[86 911 Targa]

Scott,

I think that gregwils is correct.

Someone, prior to your ownership of this car did a
"cut and paste" to resolve some type of anomoly.

Following in that individual's footsteps is not a good idea.

Since we don't know what this individual was trying to correct,
here are a few ideas.

1. Verify that the lamps are the correct P/N.
Transposing a dual filament bulb for a single filament bulb
can cause these types of issues.

2. Using the schematic that gregwils sent you, verify
the color codes and harnesses to each lamp.

You can purchase a Fluke 77 meter on eBay for about
75 bucks (used). they are great for around the house,
and around the car.

This issue may take some time, but when resolved,
it will be a big +.

You may email me if you need any further assistance.

Good luck,

Gerry

_____________________
1986 Targa-Factory Delivery.

[1986911]

Hello Scott, I have an 86 Targa and double checked some things for you. The headlight switch does not illuminate. The only one that does is the fog light switch. It turns on and dims with the other panel lights. It also turns on completely when the fogs are turned on. The headlights have to be on and the ignition open for the fog light switch to light all the way.

As far as your pesky problem it seems that that grey #7 circuit coming from the fuse box is chafing somewhere along its path to the license plate lights. Its chafing up against a constant power wire and the draw is probably due to the constant power wire going to ground via the filament at the license plate lights. The bigger the chaff the bigger the draw. The draw is too little to probably light the bulbs. To confirm, disconnect the wires from both license plate light fixtures. In other words get rid of any path to ground. Before cutting/ disconnecting the wire at the rear recreate the draw, confirm with meter then cut its legs off at rear of car.


If confirmed, a solution would be to follow that grey wire fuse #7 all the way back to try to find the chaff. If not, then your only choice would be to run a new fused wire to the rear of the car. This should do the trick.

If it does not, reinspect the wiring repaired by the previous owner's pro. There may be an issue at the switch. Not likely because the draw is after fuse #7.

Good luck

[1986911]

I never asked if the grey wire was still connected at the rear of the car? My mistake for ASSuming.

If its disconnected then your best bet would be to find out why its disconnected. If you cannot then run a new grey wire from light to fuse. Sounds like a pain in the rear but if you can figure out a 380 ma current draw it should be no sweat! The previous owner took a shortcut made that jumper instead of doing it right.

Another option (last resort) would be to have a stereo or alarm shop run the wire for you. Just make sure to connect the new grey wire to the same spot in the fuse box.

Hope this helps

[deshetlr]

Thanks guys. I will take the pointers and head to the garage. It was also suggested I use a meter to check the power and ground sides of the wires that are factory attached to the license plate lights. I will keep you informed. Here are a couple of photos of the mess. Oh I forgot to mention the chassis ground on the right side was loose; the bolt being about 1/2 way in. I cleaned it and tightened it down with no apparent improvement.

[deshetlr]

Does anyone know where ground point G414 is located? The grey wire come to the back of the car in a loom of other wires and then eventually splits to the 2 plugs that go from inside the engine bay to either taillight assembly. Both lights are dead so I am assuming if there is a chaffing issue it is between the fuse block and where they split. Could be an adventure to find that!

[86 911 Targa]

Scott,

There is a 10mm grounding point in the engine compartment, on the driver's side.
It also serves a a grounding point for the defogger elements, heater blower motor ect...
which may be G414.

You should be able to locate the short (if that is the problem) with your multimeter
by lifting wires until the draw disappears.

Good luck,

Gerry
_______________________
1986 Targa-Factory Delivery.

[rick-l]

I looked in the factory manual for the 86. It shows a green wire and a brown wire in the plate light.

The brown wire from the plate light and the brown wire from the rt tail light go to MP XIV which is listed as Ground - impact damper right.

It looks like the red wire (added) either provides a ground for the taillights or the plate light that was broken.