making up a rear fog light

[reut1]

So I want to take my left reverse light and make it into a rear fog by putting a red LED bulb in it. I am going to get another fog switch to put in the blank spot up by the front fog switch. What else would I need to complete this? Do I go the route of getting an add-a-fuse type thing in there or should i come right off the battery and put an inline fuse in the set up.

I want to wire it in such a way that it turns off when the car turns off. I dont want to tie it into the front fogs since I use those as driving lights during the day.

 

[pasadena_commut]

Check your state's vehicle code - what you are proposing sounds like the sort of thing most states would frown upon.

That said, I'm not very clear on what you are trying to do. Do you just want a red light on the back that you can switch on and off? If so, the easiest route, electrically, would be to slightly modify the existing circuit that causes the taillights to come on when the headlights are on. So no new bulbs needed. I have not looked at that diagram, but expect the most you would need to accomplish this is one switch and possibly a diode (so that the headlights do not receive power when the taillights do). In general terms (ASCII art)

                               (new diode)
       +----------------------+----|>|---------+-----------+
       |                      |                |           |
       \ (headlight switch)   |                |           \ (new switch)
       |                  [headlight]    [taillight]       |
   [12V bat]                  |                |           |
       |                      |                |           |
       +----------------------+----------------+-----------+----Ground

The existing headlight switch might actually be a relay. If the P5's headlight switch drives two relays, one for the taillights and one for the headlights, and those circuits are already separate, then you can wire the new switch onto the taillight relay and use a smaller diode to keep that new switch from turning on the headlights.

The same sort of thing could be done for the brake lights, and that would be even simpler, because there is already a switch at the brake pedal, all you need to do is wire another switch in parallel with it.

 

[justanothermp5]

i didnt read the above post, too long lol
but what i would do, is buy an add-a-circuit thing, hook it into a acc. power (switched power), run that to the switch, then run the wire to the bulb
from the bulb i would just ground it directly to the chassis. Easiest way to do it, only problem is getting the right voltage...not sure if the bulbs use a full 12v or not
so you may have to wire in some resistors or a zener diode if thats the case

 

[pasadena_commut]

I botched part of that drawing, let's try again:

                               (new diode)
       +----------------------+----|>|---------+-----------+
       |                      |                |           |
       \ (headlight switch)   |                |           \ (new switch)
       |(+)               [headlight]    [taillight]       |(+)
   [12V bat]                  |                |       [12V bat]  
       |(-)                   |                |           |(-)
       +----------------------+----------------+-----------+----Ground

If the diode wasn't in there the new switch would act just like the headlight switch, turning on both the headlights and the taillights. There would be a little loss of voltage to the taillights, but it should only be around 0.7V, and won't make much difference.

 

[reut1]

im looking more into the way that justanothermp5 suggested doing it. I dont want to tie into the existing taillight set up because i want this fog to be independent of the rest of the lighting system. I just want to make sure itll turn off when i turn off the car just in case i forget to switch it off after i finish driving. I didnt know if it could be as simple as running a wire from an add-a-fuse or not. So ill start buying some parts and piecing this together. just not sure which prongs on the back of the fog light switch i would use since im just running two wires off it and there seems to be 4 prongs

 

[justanothermp5]

hmm...ill have to look at the plug tomorrow and the wiring diagram to see which prongs are the right input/output
ill try to remember at least lol

 

[reut1]

alright. im gonna go out and look for an add-a-fuse tomorrow and another socket i can use so i dont have to cut out the existing one from the reverse light. i have thought of just running another wire from the front fogs to the back but id rather leave them out of this. where are these wiring diagrams so i can take a peak for myself?

 

[justanothermp5]

ahh...that i dont remember, I downloaded them all to my computer from a website for free, its pretty common on the boards
if you ask around you should be able to find the link to them, i believe its protege5.ugly.net/(something else), not too sure though

edit: http://web.archive.org/web/20061223062340/http://protege5.ugly.net/

that should be it
edit2: actually dam, that doesnt have the wiring diagram in it..not sure where i got it from

 

[reut1]

well tomorrow im gonna pick up an add-a-fuse, socket and potentiometer. ill wire it all together using my current front fog switch and see if i can make it work just on the floor. then ill run wires to the back later on when i order my red LED for the housing

 

[pasadena_commut]

well tomorrow im gonna pick up an add-a-fuse, socket and potentiometer.

Also a Digital Multimeter if you don't already have one. Which, judging from your previous question about the switch, you don't. One of the really cheap ones from Harbor Freight ($3?) will work fine for this.