This Question was for a 1990 Mercury XR7, I just bought it, and don't know where the switch is for the fog lights or how to turn them on, please let me know, if you know. Thanks!
If it is like my 2005, you pull the headlight switch. I know it doesn't seem like you should be able to pull out a switch that normally rotates, but that is how it works!
I believe you turn on your low beam headlights and then pull out on the selectorswitch to turn on the fog lights and then push it in to shut the fog lights off
On the 2002 Impala you need to first pull the thing that turns on the headlights manually like half way or all the way and then hit the fog button and the fog lights will come on.