help! headlight wiring question
07-04-2001, 01:15 PM
#1
Racer
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help! headlight wiring question
i am re-wiring my headlights and foglight (just got some new euro style) but i have run into a problem. the previous owner sure did screw things up with the lights on this car as the foglights don't work, and the headlights are ran in parallel (should be independent) i am going to re wire each light individually from the fuse box which is where i think is the best place to start. after pulling up the fuse box, i realized i don't have any diagrams for the bottom of the fuse box. which wiring clip contains the headlight wires (low and high beams) and the fog lights? 
any help or scematics of the bottom of the fuse box would greatly help!
- Kevin
any help or scematics of the bottom of the fuse box would greatly help!
- Kevin
07-04-2001, 02:23 PM
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just for information to anyone else trying this, it is wiring clip "C" that contains the wires that run to the headlights both low and high beam (if i am wrong please correct me, for i just used an ohmmeter to find the wire ends). My next step in this project is to locate the fog-lights wiring clip... again any help would be appreciated.
oh and it is a '87 951
oh and it is a '87 951
07-04-2001, 06:44 PM
#3
Nordschleife Master
Kevin, you are going about this the wrong way as well as being more difficult. If you are going to bother you should be wiring in relays up front to reduce voltage drop.
The only relay you have right now is one for the fogs (unbelievably there are no relays for the headlights). Don't bother tapping off the wiring under the fuse board other than switch power for your new driving lights, just use the existing light feeds down front to drive the relay coils/switches.
Pull light power from the alternator (tough to get at but shorter distance) or the battery. Use #4 gauge for that feed. Then to fuse(s), then to the relay(s) and finally off to the lights. I would use #10 gauge for those wires if you ever plan on using overwatted bulbs, otherwise #12 should be ok, though as long as you are going to the trouble, may as well use #10. Don't forget to rewire the grounds also as you are probably losing 3/4 volts there.
Right now you have seperate fuses for each filament in you headlights (4 total) for safety reasons, i.e. short one out and the other side keeps working. I don't think I would keep that, and cut things down to just 2 fused and relayed circuits. Otherwise you are going to have lots of relays down front.
The only relay you have right now is one for the fogs (unbelievably there are no relays for the headlights). Don't bother tapping off the wiring under the fuse board other than switch power for your new driving lights, just use the existing light feeds down front to drive the relay coils/switches.
Pull light power from the alternator (tough to get at but shorter distance) or the battery. Use #4 gauge for that feed. Then to fuse(s), then to the relay(s) and finally off to the lights. I would use #10 gauge for those wires if you ever plan on using overwatted bulbs, otherwise #12 should be ok, though as long as you are going to the trouble, may as well use #10. Don't forget to rewire the grounds also as you are probably losing 3/4 volts there.
Right now you have seperate fuses for each filament in you headlights (4 total) for safety reasons, i.e. short one out and the other side keeps working. I don't think I would keep that, and cut things down to just 2 fused and relayed circuits. Otherwise you are going to have lots of relays down front.
07-04-2001, 07:01 PM
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after 5 hours i got the entire light system working! the euro lights work excellent and i left only one thing out. power relays for the new driving lights. i have one relay, but need to order another so i can finish the job. surprisingly the only problem that was wrong with the car was the ground to the right head light. i fixed that problem and finished installing the new fog lights. i didn't need to tap into any lines as they were already there. i think given more time i will install larger cable to reduce the voltage loss. thanks for the information iceshark i will follow your recommendation next time i am working on this.
07-04-2001, 07:32 PM
#5
Nordschleife Master
Kevin, now that you have things working, take a volt meter, start the car and turn on all the lights (headlights, fog and driving, if you can) and take a reading of the voltage at the battery and then down at the light sockets.
That will tell you how much your wiring is allowing the light voltage to drop and what you want to do about it. As voltage drops it will reduce the light output, but the reduction is very extreme about to the 3.5 power. Over a cubic function - if your bulbs are 100% at 13.5v , output will be only 53% at 11.5v.
This is why it frequently is not worth the trouble to put in overwatt bulbs unless you rewire. The additional amp load and tiny and corroded OEM wires causes such a monster voltage drop that you are back to square one. And maybe even worse if the wires melt.
That will tell you how much your wiring is allowing the light voltage to drop and what you want to do about it. As voltage drops it will reduce the light output, but the reduction is very extreme about to the 3.5 power. Over a cubic function - if your bulbs are 100% at 13.5v , output will be only 53% at 11.5v.
This is why it frequently is not worth the trouble to put in overwatt bulbs unless you rewire. The additional amp load and tiny and corroded OEM wires causes such a monster voltage drop that you are back to square one. And maybe even worse if the wires melt.