Parking light out electrical diagnosis advice

[GriffinPrice]

Hello all,
The driver's side parking lights on my '84 Targa have not worked since I got it back in January. I bought some replacement bulbs (knowing that multiple lights being out was almost certainly not a "bulb problem" but hoping anyway) and of course the problem persists.

I am planning to take a multimeter to the car this week or next to try to diagnose the problem, but I'm a bit nervous about fiddling with the electrical system of a car that is new to me and whose previous owner seems to have been a lazy idiot. I would appreciate it if someone could chime in with ideas or suggestions.

Here's the information I have been working with:

• The fuses were old and corroded. I removed them and added new ones, but the contacts still aren't in great shape. Driver's and Passenger's parking light fuses appeared identically corroded, but only the driver's side is out.
• On the top side of the fuse panel, the passenger's side fuse had a wire connected to the fuse terminal. The driver's side fuse did not. From what I have read, they are electrically connected on the back side of the fuse panel. Is there any risk of this not working?
• There was a bundle of wires behind the tail light assembly when I pulled it out a little bit to check the connector into the back. I couldn't get a good look at it, but it looked like it was not done by a professional, so I'm suspicious of it.
• My best course for diagnosis is to just run along the circuit with a multimeter and try to identify where the opening is. I can do this by activating the circuit with the switch inside the cabin and then putting one probe on the circuit area I am interested in and the other probe on the frame. Is this correct? Worst case, I can run a ground wire out to where I am probing, but I'd prefer to avoid that if possible.
• Would one element being out cause the whole circuit not to work? As in, does one dead bulb screw everything up? I guess I'm asking if the lights are all in series, which would be ridiculous but that's how the PO of my old Sprite did the headlights.

Does anything big jump out to y'all? I've been noodling on this for a while, and the bundle behind the tail light assembly seems like the most likely area where something is bad, but I'm open to any smart ideas. I've exhaustively searched the forums and not found anything exactly like my issue that had a clear resolution.

[snbush67]

Yes, it can just be the bulbs, I just went through about 2 weeks of troubleshooting a similar issue that ended up being that I had the wrong bulbs. Double check all of the bulbs, make sure double filament bulbs go in the right bases and that the single filament bulbs as well. Clean the contacts.

[creaturecat]

did you test for power with a test light?
did you test the ground with a new "temporary" wire?

[GriffinPrice]

So I went through the rigmarole of tracing the electrical path of (I thought) the parking lights.

Unfortunately, the electrical diagram I had found online was not from an '84, and I was looking at the wrong fuse. I figured this out after testing contacts along the electrical path and seeing that everything appeared to have a continuous line. The smoking gun ended up being resistance; there were a few ohms between battery hot and the light sockets.

After consulting the Fuse diagram in Bentley's, I was able to see that I had been examining the wrong fuse for failure. After cleaning the contacts around the true fuse, the lights turned on again. Good grief! I'm just lucky that I didn't spend too much time banging my head against the car to try to evaluate the true cause of the issue. Now I just need to figure out why the trunk light still doesn't work! It's the only thing on that circuit that isn't functioning properly, even after replacing all bulbs and cleaning off the fuses.

Thanks a ton for the help! I've never experienced a circuit failing because of high resistance, but now I have that diagnostic method in my toolbox. This car is teaching me so many good lessons.

[snbush67]

Glad you found it. Thanks for the follow up!

The frunk lights are often disconnected by a PO because they can drain the battery quickly, if they aren’t adjusted right they can stay on even when the trunk is closed. First test is to see if there is power at the switch. When the switch is closed (trunk open) the power should flow to the light. Again it could be the contacts inside the switch or bulb housing. Or the bulb could just be blown. Good luck.

[Treadway597]

Originally Posted by GriffinPrice

Hello all,
The driver's side parking lights on my '84 Targa have not worked since I got it back in January. I bought some replacement bulbs (knowing that multiple lights being out was almost certainly not a "bulb problem" but hoping anyway) and of course the problem persists.

I am planning to take a multimeter to the car this week or next to try to diagnose the problem, but I'm a bit nervous about fiddling with the electrical system of a car that is new to me and whose previous owner seems to have been a lazy idiot. I would appreciate it if someone could chime in with ideas or suggestions.

Here's the information I have been working with:

• The fuses were old and corroded. I removed them and added new ones, but the contacts still aren't in great shape. Driver's and Passenger's parking light fuses appeared identically corroded, but only the driver's side is out.
• On the top side of the fuse panel, the passenger's side fuse had a wire connected to the fuse terminal. The driver's side fuse did not. From what I have read, they are electrically connected on the back side of the fuse panel. Is there any risk of this not working?
• There was a bundle of wires behind the tail light assembly when I pulled it out a little bit to check the connector into the back. I couldn't get a good look at it, but it looked like it was not done by a professional, so I'm suspicious of it.
• My best course for diagnosis is to just run along the circuit with a multimeter and try to identify where the opening is. I can do this by activating the circuit with the switch inside the cabin and then putting one probe on the circuit area I am interested in and the other probe on the frame. Is this correct? Worst case, I can run a ground wire out to where I am probing, but I'd prefer to avoid that if possible.
• Would one element being out cause the whole circuit not to work? As in, does one dead bulb screw everything up? I guess I'm asking if the lights are all in series, which would be ridiculous but that's how the PO of my old Sprite did the headlights.

Does anything big jump out to y'all? I've been noodling on this for a while, and the bundle behind the tail light assembly seems like the most likely area where something is bad, but I'm open to any smart ideas. I've exhaustively searched the forums and not found anything exactly like my issue that had a clear resolution.

If the right side works it’s not the switch. Look at the right side position of the brake light when it is on, then check that position on the left for a bulb and change it. I would start there.

DG Customer First

[timmy2]

Originally Posted by Treadway597

If the right side works it’s not the switch. Look at the right side position of the brake light when it is on, then check that position on the left for a bulb and change it. I would start there.

DG Customer First

He fixed it. Read post 4.