Help with independent fogs

[Platypus]

Would like to run fogs independently. Through Search I’ve found a couple of old posts. One suggesting removing or redirecting the two brown wires at one of the high beam fuses. No brown wires here... I’ve disconnected the two wires (one at a time and both) at the high beam fuse that does have two wires at the bottom. Only change being, no high beam function.

I do have a low beam fuse blown, fails upon light switch activation. Leaving me with one (driver-side) low beam. Both high beams work. But focusing on getting independent fogs first. Unless the blown fuse negates trying to get the fogs to work independently.
1977 911S
Any help appreciated. My fuse box;

[Platypus]

Bump.

[kev01]

Fuse 1 is usually foglight. Does you car have foglights fitted and wired up from factory?

[darrin]

what currently needs to be on to get your fog lights to work? -- on my '86, they previously required my low beams to be on (and used a wire coming from the low beam fuse to power the fog lights) -- I moved this wire YEARS ago to attach to my parking light circuit so that I could power my fog lights whenever my parking lights were on.

[Platypus]

Kev01 Yes fitted,wired, factory fogs.

[Platypus]

Originally Posted by darrin

what currently needs to be on to get your fog lights to work? -- on my '86, they previously required my low beams to be on (and used a wire coming from the low beam fuse to power the fog lights) -- I moved this wire YEARS ago to attach to my parking light circuit so that I could power my fog lights whenever my parking lights were on.

They come on with the low beams.

[darrin]

Does more than one wire come out of the bottom of your low beam fuse? If so, likely that one's there to power/energize your fog lights -- isolate that wire (i.e. if removed foglight don't come on but low beams do) and you can then determine what circuit you want to use to power the fog lights -- if fog lights aren't already on a relay, you might want to add a relay so that the triggering wire isn't carrying a load (and potentially overloading the triggering circuit)

d

[Platypus]

Originally Posted by darrin

Does more than one wire come out of the bottom of your low beam fuse? If so, likely that one's there to power/energize your fog lights -- isolate that wire (i.e. if removed foglight don't come on but low beams do) and you can then determine what circuit you want to use to power the fog lights -- if fog lights aren't already on a relay, you might want to add a relay so that the triggering wire isn't carrying a load (and potentially overloading the triggering circuit)

d

Thanks, only seeing one wire to bottom of both low beams. Will have to take a closer look and move some wires around...

[darrin]

trigger should be from low beam (per your explanation above, when low beam circuit energized, your fog light circuit's powered up and allows your fog lights to come on when energized by your fog light switch)

[Platypus]

Originally Posted by darrin

trigger should be from low beam (per your explanation above, when low beam circuit energized, your fog light circuit's powered up and allows your fog lights to come on when energized by your fog light switch)

Thanks, makes sense and it seems as this is how they are operating. Just need to find the trigger wire.

[Koizumi]

Move the grey fog trigger wire to a switched power fuse.

Then you can have just fogs, parking lights + fog, lo + fog or hi + fog. In essence, independent of everything else. Or shut off the fog switch and have no fogs until u want them on.

I just leave the fog switch pulled out all the time and they turn on when the car is on w/o any other lights on - as daytime running lights.

[fred cook]

According to a diagram I have, fuse 1 should be the fog light circuit. It should be a white/green going in the top and yellow or yellow/white out the bottom. The fuse should be a 15 amp. You can pull the fuse that is blowing and use an ammeter across the two fuse terminals to see how much load that circuit is pulling. Sounds to me like there is a short either in the wire going to the right low beam or in the bulb itself. Since that wire is only going from the fuse panel to the light unit it should not be too hard to trace. After checking the load, I would unplug the headlight and see if the fuse continues to blow. If so, you will know that the problem is in the wire. If not, the problem is in the light. Someone may have installed a high wattage bulb that is pulling more than 7.5 amps (white fuse rating). If I remember correctly, divide wattage by volts to get amperage draw. Happy hunting!

[Platypus]

Originally Posted by Koizumi

Move the grey fog trigger wire to a switched power fuse.

Then you can have just fogs, parking lights + fog, lo + fog or hi + fog. In essence, independent of everything else. Or shut off the fog switch and have no fogs until u want them on.

I just leave the fog switch pulled out all the time and they turn on when the car is on w/o any other lights on - as daytime running lights.

Yes, wanting basically drl via fogs... thanks, will give that a try.

[Platypus]

Originally Posted by fred cook

According to a diagram I have, fuse 1 should be the fog light circuit. It should be a white/green going in the top and yellow or yellow/white out the bottom. The fuse should be a 15 amp. You can pull the fuse that is blowing and use an ammeter across the two fuse terminals to see how much load that circuit is pulling. Sounds to me like there is a short either in the wire going to the right low beam or in the bulb itself. Since that wire is only going from the fuse panel to the light unit it should not be too hard to trace. After checking the load, I would unplug the headlight and see if the fuse continues to blow. If so, you will know that the problem is in the wire. If not, the problem is in the light. Someone may have installed a high wattage bulb that is pulling more than 7.5 amps (white fuse rating). If I remember correctly, divide wattage by volts to get amperage draw. Happy hunting!

Thanks for the input. Will go hunting.

[Canada Kev]

Or you could move the grey wire (fog light) on the rear of your headlight switch to pin 75 which is energized at any time your car is on. This will send power to your fog light switch, again, whenever your car is on.

This allows you to turn on the fogs (or off) at any time; if the car is running (or ignition switch on) your fogs will operate, either on or off, as per the fog switch, regardless which other lights are on.

[Bitte ein Bit]

Originally Posted by Koizumi

Move the grey fog trigger wire to a switched power fuse.

When you say to a "switched power fuse" - can you/someone give an example? I have been wanting to do something like this (independent fog lights) as I really want to use as daytime running lights. 86' Coupe here.

Really glad I found this thread as I learn electronics...

Subscribed!



Erik

[Koizumi]

Originally Posted by Bitte ein Bit

When you say to a "switched power fuse" - can you/someone give an example? I have been wanting to do something like this (independent fog lights) as I really want to use as daytime running lights. 86' Coupe here.

Really glad I found this thread as I learn electronics...

Subscribed!



Erik

For my ‘84 Coupe:

I moved the fog light relay trigger gray wire to fuse #5 which is the fuse for “Outside Mirror and Heating/AC Control Module”

It’s quite simple.

It’s very nice to have independent fog light control - especially as daytime running lights.

Cheers

[86 911 Targa]

^^^^^
Do this.

Best,

Gerry

[Platypus]

Ok, Canada Kev and 86 911 Targa, interesting, and thanks. Looks like there’s more than one way to skin a... er, solve a problem. Getting some dielectric grease and will see if I can get to this today. Now to decide what direction to go. Ha.

[Platypus]

This went about as well as I expected. As I got half way there, the long way. I pulled the headlight switch to see if I could move the grey wire to pin 75 as suggested. No grey, grey/white wire there, and a red/white wire already occupying pin 75. Tried a few things, no success.

I ended up moving the grey wire from fuse 5 (right low beam) to fuse 4 (parking lights) and got one independent fog left (driver) side. With parking lights on. Grey wire is not long enough to reach fuse 11 as suggested above.

So now to figure out the right side blown low beam fuse. Fog light is also out on that side, so I’m guessing wire? Next warm day...