I have seen everything for 97+ fog light switches. But, nothing for older. I have a three wire termination ( black, ligt blue and brown/white). Presuming black is ground, which of the other two are 12V in and 12V out?

 

Black is the ground. The brown/white would be the 12V in. It connects to the park lamp relay and is the control circuit for the park lamp relay. It is a low power circuit. When you turn the fog light switch to on, Brn/wht connects to the black wire for a ground to turn on the park lamp relay. The light blue wire is a dead end wire. It connects to the 2 fog lights and to high beam relay. With the switch in the off position power is going nowhere.

When you turn your headlights on, power is also sent to one side of the park lamp relay control circuit. The other side is the brn/wht wire. When you turn the fog light switch on, this provides the ground to activate the park lamp relay to the on position. Now power from another fuse source goes thru the park lamp relay and the high beam relay to the fog lights. The lights turn on. When you use the dimmer switch for high beam, this activates the high beam relay which cycles to turn off the fog lights while high beam is in use.

I'm not sure why the Lt blu is connected to the fog light switch. It seems that the circuit would work without it. But what the heck do I know.

Anyway I hope this is understandable. It is easier to look at the schematic than to explain it.