Electrical Issues (Lighting)...Help Please!!!

[M491]

I'm having some electrical issues I can't figure out and would like to ask you for your expert help, please.

The car in question is a 1972 911T. It's basically a time machine, since it had, until quite recently, been sitting unmolested (almost) since 1989. Everything is there and original, down to the original radio and speaker.

Here's what is going on:

--All bulbs are new and all contact points in the sockets have been scrubbed to remove any oxidation.

--All fuses are intact.

--Both brake lights work fine.

--Reverse lights work fine.

--The parking lights, front and rear, on the driver's side are dead. Strangely, randomly, one day the parking lights on the driver's side worked. The next day, and never again since, they were dark again.

--The turn signals and emergency flashers work on all four corners.

--Leaving the turn signal switch on to the right when the igntion is switched off results in the turn signal lights remaining on (Euro feature). This feature does not work when the turn signal switch is left on to the left and the ignition is turned off.

--The little side marker lights do not work on either side in the rear, but the passenger side front does.

--The high beam headlight works on the passenger side, but the low beam doesn't.

--The low beam headlight works on the driver's side, but the high beam doesn't.

--In the tachometer, both right and left turn signal (green arrow lights) light up, whether the turn signal switch is to the left or the right. I think only the left arrow should light when turning left, and only the right when turning right. Both arrows blink, correctly, when the emergency lights are switched on.



I am at my wits' end to figure this out. Do these symptoms point to a single or multiple problem area to those electrical gurus among you? Where should I start, and how do I test various points in the switches and wiring? HELP!!!

Thanks an advance for any and all advice, information and pointers.

[Rich Lambert]

It would be helpful to know how much electrical troubleshooting experience you have.

It definitely sounds like you've got multiple issues going on. Get yourself a good schematic, a magnifying glass (so you can see the tiny drawings of the inside of the relays & switches), and a multimeter. Troubleshooting is basically like following a road map. Wires go from point-A to point-B. Focus on one problem at a time.

Start with the easy stuff. At the fuse panel, check the wires, fuse ends, and fuse holders for corrosion and that all the screws are tightened down. Don't forget to disconnect the battery first.

"--The parking lights, front and rear, on the driver's side are dead. Strangely, randomly, one day the parking lights on the driver's side worked. The next day, and never again since, they were dark again." This one sounds like an easy one...pull all the parking light bulbs and, with the switch on, check the sockets for (+) and (-) voltage. You'll probably find a bad ground connection somewhere.

Keep us informed as to your progress.

[silverc4s]

Find and clean all of your ground connections. This is a group of Brown wires bundled together & bolted to the chassis in various places. There are 2 or more locations behind the instruments, and one in each front fender if I recall.

Also, check all the wires going into the headlamp plug, AND the wiring socked on the fender that goes to the headlamp on each side. I have seen these wired incorrectly by PO to "fix" a problem, then left in this state.

Also make sure that the contacts on your turn signal switch are clean and not stuck together. You may want to purchase the "Sucro Relay Kit" for this area. Do a search, it's a $20 or so fix for a known weak area.

[Mr9146]

The majority of electrical problems in these cars can be traced back to one thing: Earth.

If you've got electrical issues, check the grounds.

[M491]

Thanks everyone for the advice and info. As it turns out, I did have two distinct problems. The previous owner installed some sort of cut-off switch, and had wires connected to the gauges and fusebox. Some of the wires had been removed/cut/disconnected. This was causing some of the issues. Secondly, the problem was hiding in plain sight. It is usually the case that the solution is the simplest one. The ends of the fuses were corroded. I had cleaned the fuse block connectors, but neglected the fuses! Now all of my lights are working A-OK (except the rear pax side side marker light). There's no power to that little socket. That is not such a big deal to me. I should be able to fix that. Thanks again everyone.