Help with independent fogs
 

Btw, thought I’d mention it: I had to add an extension of wire to the gray wire to make it long enough to move it to fuse #5. You can move it to another switched fuse but note the amperage of the fuse and match it to the fog light relay! It should be 16A!!!! Fuse #5 is rated at 16A just like the fog light relay, and it is also a switched fuse.

Great idea. Can this light switch alternative be done on older cars with fogs?
I have a 78 and wouldn’t mind trying this.

I don't know, but without looking at that specific wiring diagram, I don't see why not. I'm pretty sure even those had a factory fitted fog light relay.

Personally, if it were me and I wanted to find out, I would pull out the headlight switch from the dash and see if the grey wire was there. The older cars might use a different colour, so keep that in mind.

If the fogs currently only work when the headlights are on, the trigger wire for the fog relay is probably on terminal 56 along with the headlight wire. This is the only terminal energized when both the key is on AND the switch pulled out to the second detent.

With the headlights turned on and illuminated (key has to be on as well) turn on the fogs as well. Remove the wire from the back of the light switch and see if the fogs go out. If so, there's your fog light wire.

Now you can put that wire on any terminal that fits your operational requirements. For me it was #75 which is energized at any time the ignition switch is turned on so that the fog relay got power whenever that condition was met, and thus, the fogs could illuminate when the fog switch was turned on.


If you want them to work any time your running lights are on, use #58, 58L or 58R. Be aware that the fogs will not turn off if the ignition is off (unless fog switch is turned off).

If you want them to turn on whenever the fog switch is on use #30 which is always energized. Again, the fog relay is also still energized with the key off.

If you want them to turn on at any time only the running lights are on but not with the headlights, use #57. Fog relay is still energized with the key off like this.

For me, the only valid alternative to using #75 is to have them work whenever the parking lights and headlights are on, but also to turn off with the ignition key, use #N.

Also be aware that your headlight switch may not have all of these terminals. My spare headlight switch is missing at least one of those terminals as it is from an earlier car. I think it may be missing terminal N. I drew up a headlight switch matrix a few years back that listed the conditions under which every switch terminal would operate. If you need to use it, I've attached it to several headlight and/or fog light threads here. Should be easy to find if you search for 'headlight switch matrix'. Or if I find some time later, I might put it here as well.

is there a suggestion how to wire if i want on as soon as the ignition is on regardless of the switch (versus leaving the switch on)..this way when i start the car I know they are on as my daytime driving lights?

Of course seeing that you want the lights on all the time, the switch becomes redundant and useless to that application. The simplest way would be to connect a 12 volt source that is only energized when the ignition is on and connect it to the trigger terminal on the fog light relay.

The issue that I foresee using that method is that you would be in violation of laws in just about every province and state about running fogs or accessory lights with headlights at the same time, ie. failure to dim lights. Not usually a big deal during the daytime, but at night it might offend the sensibilities of certain people in your local constabulary. I got a ticket for that a few years back by running fogs with headlights while in town. I had a burned out headlight and no spare bulb until stores would open the next day. I thought having my fogs on was a better alternative than only one headlight. The cop disagreed. Maybe nobody would bug you, maybe they would.

In that case you could use a normally closed relay on the fog trigger wire, before the fog light relay and have it triggered from the headlights. When the headlights go on, it triggers this additional relay to become open, thus breaking the circuit to the fog lights. So, headlights on, fogs off, headlights off, fogs on.

Platypus, great advise you were given here.

1. First I will keep wires in their factory setting location before moving anything.
2. Fix that low beam issue; check continuity as it must be a burnt/grounded wire.
3. The white with green stripe cable on no.1 is the front fog light wires which connects to the dash factory fog light switch. It will only work on low beam only!
4. I see too many 8 amp fuses (white) in that panel for the headlamps. Will have to check, I believe more amps are needed for the headlamps. Your fogs have a 25 amp(red) fuse there.

Since yours is a 77 you can do a little switching around depending what you want. Tell us what do you want to do? Permanent fog lights as driving lights? Independent fog light switch? Remember electrical things must be working before making things worse...

Jose

Indeed... Yes started to dig into low beam/fuse out today. As fredcook suggested I;

Checked the load, appears to be normal. Both headlights drawing the same at their fuse terminals @7.2 amps

Unplugged the headlight, put a 8 amp fuse (ivory) in. Turned car on, pulled headlight switch to on. Did not blow a fuse.

Reconnected headlight with fuse in place, headlight switch to on. No blown fuse, but no light either. No fog on that side either. Weird.

Checked bulb and connections and I’m not seeing anything amiss, other than the dead bug on the harness...

So more hunting to do. Maybe the high beam on/off stalk switch-relay?
A few photos of the process;


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good! I see that you are testing with a multi-meter. Insure that you have current to the three cable headlight plug. You should have a brown cable for ground and the other two are low and high beam; test all to see what you have. On the brown ground cable look to see if you have good ground. That connector is covered with red paint clean it well and let us know what you have. PM me if you wish and I will give you more ideas.

Thanks, will do. Will have another look, hopefully tomorrow...

Here ya go See post #3 http://forums.pelicanparts.com/porsche-911-technical-forum/382588-running-fog-lights-only.html

Thanks. Have a non functioning headlight/fog light to figure out first.

Switch the bulbs back and forth to rule out bad bulbs unless you are getting zero power.

To the OP,
for your '77 wiring, It may help to have the bottom fused wires going to the high and low beam lamps in the correct fuse positions.

The yellow and yellow/green currently in 7&8 should be below the top yellow wire in positions 5 and 6 from the front.

The Blue and Blue/White currently in 5&6 should be under the white wire for positions 7 and 8, leave the white blue high beam indicator wire where it is. (bottom of fuse 8)

Then the fogs should go on with the low beams as is normal.

You can then move the Grey wire in the top of fuse 5 to wherever you want!
Try Fuse 2, to go on with running lights, Try Fuse 12 to go on with switched power, or leave as is.

All fuses from 74 to 83 are numbered starting from the front of the car by the headlights as per the current diagrams.

This should help you get them correct. S means fuse.

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Surely, while the OP is in there he should be fitting relays to prevent the light switch from burning out; everyone should fit relays to the headlights to reduce current through the main light switch.

Absolutely agree, but first get it all wired correctly and working.
Then start modifying/improving.

This is my fuse block set up on my 78. I also included the page from the owner's manual. I have the obvious gray wire on fuse # 2 also, plus it looks long enough to move it to fuse #11 which is used for brake lights, etc. and uses a 16 amp fuse am I correct??
I put the relay and actual fuse for the fog lights back in already.








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Thanks, so much. I’ll try this later today...

Wondering why, previously, before the blown fuse everything seemed to work as intended?
And upon studying the wiring diagram compared to my fuses, it seems the top Yellow and white wires to fuse 6 and 8 are reversed? No concern there, just leave the tops and switch the bottoms as mentioned?

Tops are correct,
Yellow is low beams can be on 5 or 6.
Blue is high beam, can be on 7 or 8.

Success! Thanks for the info. Thanks everyone for responses and suggestions!
My fuse box is rewired as per timmy2’s instructions. Grey wire previously connected to to top of fuse 5 now connected to parking lights (fuse 4) because wire is not long enough to reach fuse 12.
So the fogs are dependent on parking lights but independent of headlights. And my right headlight is working. My right side fog light bulb was out. Replaced that.



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Not sure if this light was on previously upon turning ignition to on, without lights on. but it is now....
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