Need help with Head-Light issues

[PorscheAmateur]

Hello everyone,
first let me provide some background information: I bought a 1979 Porsche 911sc with my dad's permission back in September to fix up a couple little issues over the winter and have an awesome first car daily driver when spring came around. One of the issues that i have noticed while going through the car is that the headlights don' appear to have proper illumination when turned. Both low beams and high beams work, but they barely put out enough light to see even 5 feet. This being said, i took that the headlight assembly apart with difficulty and determined that the previous owner had upgraded the lights and assemblies to the bosch h4 type. when i looked at the electrical connections, it just didn't look right. So as of now, it sits partly disassembled. Any help including electrical diagrams would be extremely helpful. And also, there are no fog-lights on my car if that helps in determining potential issues. Thanks

[gsmith660]

Try touching 12 volts directly from the battery to each hi and low beam if bright then it is an issue with the existing wiring if not then try grounding directly to battery and see if the light gets bright it is a grounding issue

[PorscheAmateur]

Originally Posted by gsmith660

Try touching 12 volts directly from the battery to each hi and low beam if bright then it is an issue with the existing wiring if not then try grounding directly to battery and see if the light gets bright it is a grounding issue

How would i go about connecting the lights up directly to the battery?
Thanks

[gsmith660]

You have to take the headlight off and touch a wire to each of the hi and lo terminals do determine which one is your ground before you play with hot wires

[Reifle]

Take a length of wire and run it from the battery directly to the lts. Figure out which prong is high and low. Touch the wire to the prong and see if the power increases/decreases. You may need to install a relay system for your headlights which is available from our host. This does help quite a bit - it takes the load from the switch and actually improves the "flow" of electricity. Clean up the connectors as well - they might be full of dust/dirt and causing some issues. Good luck!

[gsmith660]

Do you have a haynes manual? If not you need to get one. You have H-4s with a painted trim ring it looks like so to take a headlight off you look at the bottom of the light and you will see a screw you take that off and you can carefully take off the trim ring, under this is another screw the first one screwed into you take that one out and that frees up the headlight assembly. Take a multimeter and figure out which connection is the ground and mark it then as said above touch a wire from the positive connection on the battery to the other 2 connections and see if the light is bright or dim and then go from there.

[ossiblue]

Before you do any of the suggested checks mentioned above, you may wish to post a picture of the wiring and the connectors for each light, including where the wires that go into the connector are spliced. This could allow a visual clue as to if the ground wire has been connected to the wrong terminal.

[86911tlcab]

if the lights actually come on, wouldnt that mean there is power going to the lights...or could there be only two or three volts going to the lights? Truly a question as have a similar issue on another car. Can the wiring have too much resisitance not allowing 12v to the headlights?

[timmy2]

Wiring diagram here:
http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_78SC_USA.pdf
or here:
Pelican Parts - Porsche 911 Parts Listings & Diagrams
The '78 diagram will be correct for your car.

[gsmith660]

Yes verify the lights are in fact wired properly when I installed my H-1s years ago I had to move wires around to get the proper wire to the proper light and when I did my HID project I had to change them around to make them work properly again and I think if you have the ground on one of the lights then the ground would have to go through the filament which would be high resistance and the other light would dimly light up and the if you for instance go from Lo to high then the light should also light up because you just applied 12 volts through the ground. Either way I think if you have the ground on one of the 12 volt inputs then when you turn on the lights both filaments would light dimly and since your high resistance is in the filament then you may or may not have melted wires. I hope you could follow the logic I propose.

[gsmith660]

What car? On my old Chevy blazer if the ground was dirty or loose the lights would be dim or actually the current would find a different path and light up different lights clean up the ground and all would function correctly

if the lights actually come on, wouldnt that mean there is power going to the lights...or could there be only two or three volts going to the lights? Truly a question as have a similar issue on another car. Can the wiring have too much resisitance not allowing 12v to the headlights?

[Cooper911SC]

I would start by removing the headlights, cleaning the connectors and making sure they have good contact.

Remember that *most* of the time on our cars, Brown is Ground.

Great first car BTW!!

Cooper

[donagain1]

Heya PorscheAmateur, you didn't directly allude to your age in your post, but left us with a hint that your a bit on the younger side and possibly trying to become a "made man" (as they say in the mob films) by troubleshooting your Porsche. If that's the case, then I, for one, am proud of you. There's nothing like getting your feet wet working on something you love, and no better place to find help than on this forum. Some of the advice may seem a little intimidating to a novice, but don't let yourself get flustered.

Troubleshooting auto-electric problems can range from elementary, if there's only the battery, a fuse, a switch, the device, and the ground involved, to bafflingly complex if there's solid-state control devices in the mix. Take it one step at a time, and you'll gain confidence as you go. There are a few basic electricity online tutorials you can access on the web, and armed with that overview along with a few basic tools it's surprising how many things on our cars you can figure out, and tasks you can accomplish.

If you're already experienced at this, please forgive me, but from the nature of questions you posed it suggests otherwise. No worries, we're here. If you don't have a multimeter (or the experience using one) that would be a good start. Failing this, at the very least a test light (similar to the one in the photo) can be nearly as effective for many tasks. The cost is around $3 bucks at Harbor Freight, and $5-6 at most autoparts stores. It will tell you if battery is there, yes or no, by lighting up... simple as that. If it lights, most often your lights should light, your blower motors should run, etc. A meter will tell you if voltage is weak for some reason, and that is good knowledge to have in cases like what you're trying fo figure out now. Good luck, and don't be afraid to post your results here for the collective brains to interpret in order to help. Be as descriptive as possible, and photos to illustrate where something is or what it looks like are especially helpful. Good luck...