foglight switch conundrum

[hook682]

Hi All, Just finished putting Hella 550's on the 83SC. THe originals never worked since I owned it (missing bulbs and cutoff wiring inside the lamp housing). So anyhow after prepping the housings and wiring I put my Fluke on the wires to check for voltage. I turned on the car and put on the headlights. I pulled the foglight switch out that is between the cig lighter and defroster knobs and the knob itself litup but no voltage to the foglights. I pushed it back in and just for *****s and grins i moved a toggle switch that is mounted under the dash to the left of the steering wheel and boom!, voltage out to the foglights. Even with the car off and flipping the switch the foglights come on. WTF?! I tried flipping that switch in the past with no results so I thought the P.O. installed it for some unknown reason. So why does the stock foglight switch do nothing and is this other switch installed by the factory/dealer? Thanks

[MattAlpha]

Pretty hard to guess why some people have things done to their cars that do not seem logical to others. Though it still seems that your original fog lights were not going to work with the missing bulbs and cut wiring.

Maybe the PO was left handed and didn't like having to use his right hand to turn the fog lights on.

Maybe he didn't like that the original switch illuminated.

Maybe the PO thought OEM fog switch was broken and installed another one he had laying around.

Maybe he had wired the original fog switch as a kill switch.

There a ton of possibilities here.

I found crap like this with my car, in fact I'm still finding things. For some reason all of the illuminating bulbs (minus the gauges thankfully, well except for the fuel tank low warning light) were missing their bulbs. Those was very fun to replace.

You can re-wire the OEM switch if you would like. Its a bit of pain though if you can't access everything from the clock's mounting location in the dash. Then you'll have to access it from the trunk by pulling out the fresh air blower motor.

Let us know what you plan on doing.
-Matt

[911pcars]

Here are some broad categories of why a circuit doesn't work:

1. Insufficient or no source voltage
2. no circuit (or incomplete circuit)
3. Load (accessory) is malfunctioning (NG)

When diagnosing, you can either check all three or eliminate whichever doesn't apply. In your case, the fog lights work with one circuit, but not the other. Eliminate no. 3 as a possibility.

"I pulled the foglight switch out that is between the cig lighter and defroster knobs and the knob itself litup but no voltage to the foglights.

It could be a faulty fog light switch or an open circuit from the switch to the fog lights. The self-contained light just tells you the bulb is functioning, nothing else.

"Even with the car off and flipping the switch the foglights come on."

Whoever installed this built the circuit so the toggle switch independently controls the fog lights, much like the headlight circuit on many cars are independent of the ignition switch position.

"So why does the stock foglight switch do nothing....:

Refer to 1 or 2 above.

"....and is this other switch installed by the factory/dealer?"

Factory or aftermarket switch - without a work order or invoice in hand, there's no way to tell who installed it. How about calling the previous owner? In the end, it's probably more important that it work properly and safely than who installed it. For example, is the circuit fuse-protected? An electrical fire is something you want to avoid. If you think you're over your head in diagnosing this, take it to your favorite tech or check back with some pics and a multimeter to talk you through this.

Sherwood