Sourcing 12v Switched near ASC Switch

[ATF]

Evening all.

I'm working on retrofitting rear fog lights on the ti. I'm going to put a switch in the existing area where the ASC switch lives. Rather than running two rather long wires to the boot, I'll just run one and source 12v somewhere under the steering column/ASC switch area. Before I start poking around, I was hoping someone has already beat me to the punch. Anyone have any recommendations?

[thesk8nmidget]

so you just need a constant 12volt switch? or an ign powered switch (only on when the key is on?)

[ATF]

Originally Posted by thesk8nmidget

so you just need a constant 12volt switch? or an ign powered switch (only on when the key is on?)

I'm looking for an accessory+ignition 12v (so yes, only when the key is in/on/running, what not.) Not a constant on (i.e. cigarette lighter).

Also I'm planning on wiring this rear fog as a brake light when I don't have it switched on as a fog Stay tuned.

[thesk8nmidget]

either way here ya go

these wires should be sorta thick and i recommend using a test light just to be safe.
but i have done a few installs on other 3 series and this is what they are.

(taken from my work database)

----WIRE---------------COLOR-----------------LOCATION-------
Constant 12V-----Red/Green or Red/Blue---Ignition Switch Harness
Starter---------------Black/Yellow---------Ignition Switch Harness
Ignition-----------------Green-------------Ignition Switch Harness

[ATF]

I think I may have been misunderstood, or I need to peak behind the knee panel. The wires you gave me above, are those directly related to the Ignition Harness? I simply need a 12v wire, that can take the load of two 21 watt bulbs. The wire needs to be hot only when the car is on (and in the area of the knee bolster/below the cluster)

[thesk8nmidget]

yep these are all located there. right where the key goes or on the other side.

these wires are correlate to the key and that ignition switch.

they will be under that knee bolster.

just find the key and then find the wires connected to the key cylinder

[aceyx]

Originally Posted by ATF

I think I may have been misunderstood, or I need to peak behind the knee panel. The wires you gave me above, are those directly related to the Ignition Harness? I simply need a 12v wire, that can take the load of two 21 watt bulbs. The wire needs to be hot only when the car is on (and in the area of the knee bolster/below the cluster)

You definitely want to use a relay for this.

Also, if you're running one wire you might as well run two. Both will go along the driver's side.

Check out Ron Stygar's site. Someone did a writeup (no pictures) of how to add them to an E36.

[ATF]

Ahhhh now I'm more hesitant to do this.. Essentially what I wanted to do was to double up the brake lights, but also just add strictly rear fogs. To prevent the actual brakes from lighting up (when the fogs are on), I would add diodes. But if adding rear fogs isn't as easy as tapping a 12v source, I'm having second thoughts. My electrical intellect kind of sucks so I'm spelling out my plans so I don't end up crippling my car.

My plan
A. Add wire (with diode inline) from existing brake circuit, to unused rear fog circuit.
B. Run wire to rear fog circuit to dash (with switch)
C. Run wire from switch to 12v source

I understand the concept of the relay, but I also agree that I probably shouldn't be tapping into the power for the ignition cylinder, that just doesn't sit right with me. Something like the carphone is much more comfortable for me (obviously this is in the center console)

[ATF]

So here's what I've been conjuring up in my head. I really would like to hear people's opinions, I don't feel like frying anything.

[aceyx]

Why the diodes/tapping into the brake circuit at all if you're running power to the rear?

[ATF]

Originally Posted by aceyx

Why the diodes/tapping into the brake circuit at all if you're running power to the rear?

So that when I brake, and the rear fogs are off, they will act as brake lights.

I'm running power to the rear to run the rear fogs.

[ATF]

Take 2. DPDT Relay used (only because that's what radioshack had, a SPDT would've sufficed.)

Open to suggestions and opinions before I go through with it! (My electrical background is fairly simple, so please let me know if I'm screwing something up, or not doing it efficiently).

So a new problem arises. Where to source 12 volt power in the rear of my car, something that won't mind two 21watt bulbs, ~ 4 Amps

[ATF]

Anyone know how to remove the black plastic trim that runs along the rear of the trunk? Where the hatch door sensor and latch all come together. It seems like it's got some kind of funky rivet. I don't want to destroy the thing though.

[John Firestone]

On the E36/2 and E36/4, you can see the fasteners have a small center pin. After you punch it out, you can easily pull out the rivets bare-handed.

BMW connects the rear fog lights directly to the light switch contacts. That does put a fair amount of wear and tear on the switch but I believe BMW banks on you using them very infrequently. Most people might need to turn on their rear fog lights once or twice a year, if that!

The factory switch gets power for the rear fog lights through extra contacts from the low beam and front fog light relays. The factory used dual output n.o. relays for both on non-NA cars to power to the second contacts.

Did BMW NA black out the rear fog light pictogram on their 318ti clusters? It is a really good idea to have an indicator warning you when the rear fog lights are on.

[ATF]

Originally Posted by John Firestone

Did BMW NA black out the rear fog light pictogram on their 318ti clusters? It is a really good idea to have an indicator warning you when the rear fog lights are on.

I don't have front fogs (or knowledge of how the initial rear fog's were powered/switched (thank you)) but to know when the rears are on, I purchased a simple SPST switch with a backlight, so it will glow amber when turned on. I also don't plan on having it on very often. There are occasions where there may be a whiteout, loads of road spray or heavy fog in the New England area, and I will use it with my best judgment (I understand that the bright light is annoying. Been there, done that, got the t-shirt).