Running Fog Lights only....

[BER]

Joe,

Try fuse #21, the power window circuit. That circuit is switched “on” when the ignition is turned on and that is what you want. I just leave my fog light knob in the “on” position, so every time I start the car I have DRL’s.

Also, make sure you are not using high wattage bulbs in your fogs. If you are, the heat from constant use can damage the lens or housing. 35watt bulbs should work fine for DRL’s. I use good quality 55 watt bulbs I got from Daniel Stern and have never had a heat problem.

[toddetch]

Has anyone tried this on an SC?

[BER]

Originally Posted by toddetch

Has anyone tried this on an SC?

Joe Payne’s car is an SC...a 1978.

[NorthernThrux]

Looking at this for my '73 as well. I keep forgetting to turn off my lights because I'm so used to them going on and off with the ignition, as they have in every car I have owned for the past 36 years. Even though DRLs only became law in 1988 or so in Canada, I had a motorcycles and then a 1980 Saab turbo and it's lights came on and off with the ignition because that was already the law in Scandinavia. I had a series of Saabs until 2005 and then Audis and Porsches, so the habit of turning lights on and off was never developed in my muscle memory.

Ideally one wants a circuit that is interrupted when the starter motor operates so that you get the full current to the starter and not the accessories. Not entirely sure what gets interrupted on my car. Right now I have the lead to the fog light switch coming from the low beam fuse and then heading to the fog light relay, which is US compliant as the fog light relay goes off when the high beams are switched on.

I have John Audette's LED headlights (also a set of his H4s in storage for "correct") and reproduction Hella 118 fogs from Auto Foreign Services which would make good DRLs. Probably best in conjunction with the marker lights.

[NorthernThrux]

Photo of said lights.

[Lyle O]

Originally Posted by Lyle O

OK, resurrecting this, as referenced from the current "LED lights" thread: I want to do this mod (use front fogs as DRLs), but my '87 seems to be different than the '84-'86s referenced here: the gray wire in the front (fuse #20) shows to be for the license plate light in my car, according to the schematic I have. Has anyone done this for an '87?? Which wire do I move? TIA.

Can anyone please help with my '87? I am still wanting to do this...

TIA.

[joe payne]

Originally Posted by BER

Joe,

Try fuse #21, the power window circuit. That circuit is switched “on” when the ignition is turned on and that is what you want. I just leave my fog light knob in the “on” position, so every time I start the car I have DRL’s.

Also, make sure you are not using high wattage bulbs in your fogs. If you are, the heat from constant use can damage the lens or housing. 35watt bulbs should work fine for DRL’s. I use good quality 55 watt bulbs I got from Daniel Stern and have never had a heat problem.

Thanks, I just tried it and still no go. I tried with the gray wire un-connected to any fuse and the fogs still run with the low beams on only. What the heck does that wire do anyway? lol!

[darrin]

all -- sounds like the grey wire is the wrong wire for (at least) some of you. from a circuit standpoint, since the fog lights only come on when the low beams are on (and the low beam circuit is energized), one of the wires coming out of the bottom of the low beam fuse(s) has one function - to energize the fog light circuit/relay. If you were to remove the wires from the bottom the low beam fuses one by one and look at the results (i.e. which lights no longer work), you should be able to identify the wire that will cause the fog lights to no longer work but allow the low beams to work. This is the trigger wire -- move it to the circuit with appropriate characteistics-- power windows, etc., if you want the fog lights to be on whenever ignitions' on, low beams if you want to run fogs w/o headlights, etc. -- and you should be good to go.

[Lyle O]

Originally Posted by darrin

all -- sounds like the grey wire is the wrong wire for (at least) some of you. from a circuit standpoint, since the fog lights only come on when the low beams are on (and the low beam circuit is energized), one of the wires coming out of the bottom of the low beam fuse(s) has one function - to energize the fog light circuit/relay. If you were to remove the wires from the bottom the low beam fuses one by one and look at the results (i.e. which lights no longer work), you should be able to identify the wire that will cause the fog lights to no longer work but allow the low beams to work. This is the trigger wire -- move it to the circuit with appropriate characteistics-- power windows, etc., if you want the fog lights to be on whenever ignitions' on, low beams if you want to run fogs w/o headlights, etc. -- and you should be good to go.

Thanks a lot for this...sounds like a plan for me.

[Autoban]

I wired my fog lights on my 86' Cabriolet to come on when the ignition is turned on. I installed a jumper wire (green color) using fuse #7 (25 AMP) on fuse/relay panel #1 as a power source to fuse #8 (fog lights) on fuse/relay panel #2. As per the attached wire diagram, fuse #8 on panel #2 only triggers the fog light relay, so it carries a very low load.
I also installed a simple on/off toggle switch so I can turn the jumper wire off in case I have to work on the car with the ignition on. I hope this helps. The wire diagram for this purpose should be the same all the way up to '89 models.

Juergen

[joe payne]

Originally Posted by darrin

all -- sounds like the grey wire is the wrong wire for (at least) some of you. from a circuit standpoint, since the fog lights only come on when the low beams are on (and the low beam circuit is energized), one of the wires coming out of the bottom of the low beam fuse(s) has one function - to energize the fog light circuit/relay. If you were to remove the wires from the bottom the low beam fuses one by one and look at the results (i.e. which lights no longer work), you should be able to identify the wire that will cause the fog lights to no longer work but allow the low beams to work. This is the trigger wire -- move it to the circuit with appropriate characteistics-- power windows, etc., if you want the fog lights to be on whenever ignitions' on, low beams if you want to run fogs w/o headlights, etc. -- and you should be good to go.

Thanks, I just checked my right and left low beam fuses. One wire per fuse. One is green and the other one is yellow. No third wire from either low beam fuse locations.

[darrin]

dug around a bit more and see that some folks have found the trigger wire inserted into the hole above the fuse -- do you only have a single wire on the top/supply side too?

[joe payne]

Originally Posted by darrin

dug around a bit more and see that some folks have found the trigger wire inserted into the hole above the fuse -- do you only have a single wire on the top/supply side too?

Solved! The gray wire on my 78sc is on the top side of the #5/low beam fuse.
I pulled it and no more fog lights. What's the best fuse to re-locate it too.
It's very short so I may have to make a jumper wire.

Thanks a lot Darrin !!

[joe payne]

What's the best fuse to re-locate the gray wire? Should I go all the way back to fuse #21/power windows?

[darrin]

GREAT NEWS -- could you reach the windshield wiper fuse without splicing? Seems that would be the closest circuit that is energized when ignition on

[joe payne]

Originally Posted by darrin

GREAT NEWS -- could you reach the windshield wiper fuse without splicing? Seems that would be the closest circuit that is energized when ignition on

I couldn't reach, so I made a short jumper to the TOP of fuse #13/Wipers.
Now it works perfectly! I can leave the fogs on and they will come on when the ignition is turned. (even the first notch).

Thanks for the help, and I hope this helps with others 78-79 SC.

[DNickel]

Long road to a simple solution, thanks Autoban.

I have the elctrical drawings and my '88 cab and went in circles yesterday. No grey wire anywhere. Had the meter out and found no connection to the relay or the fog switch.
Diagrams are missing important bits like the fog switch and the high beam cutoff.
Thought I had it with the simple solution of activating pin 86 blu/wht with 12V key switch power. Fogs were on and everything seemed well, then I noticed my car had permanent high beams! There is a feedback loop somewhere but the diagrams are redacted for simplicity.

I now have fuse 8 box 2 to fuse fuse 8 box 1 as fuse 7 box 1 was too full.
My whole car is LED except the fogs which are next from spoke and then the fuse rating will be fine.

[dugr]

Originally Posted by joe payne

I couldn't reach, so I made a short jumper to the TOP of fuse #13/Wipers.
Now it works perfectly! I can leave the fogs on and they will come on when the ignition is turned. (even the first notch).

Thanks for the help, and I hope this helps with others 78-79 SC.

Joe, This was also the case for my 81 SC. Porsche seems to have its own rules about the fuse block. It's easy to assume all B+ power runs from the bottom-up or, vise verse. I've learned to check the fuse terminals to determine which side is the B+ source so as to have an actual fused connection. Thanks for the discovery.

[7783911]

I would like to run fogs standalone as well, when installing a relay, any specific capacity required? I assume I will run power direct to relay and take pressure off swicthes?

[dugr]

If your's is equiped with factory fog lights, it has a relay in place, 2nd from the front in the frunk.