I have fog/driving lights that I bought a while ago and the wiring is messed up.
I really want to have them hook straight to the headlights. So that they come on when the headlights are on.
What wire do I need to tap to have them come on with the headlights?
First the wire....
I don't know. The best suggestion on that would be to go to the library and take a look at a Chiltons book that includes the '99 Tracker wiring diagram. Or visit a dealer service department and beg/grovel for the information. Or find a local customizing shop and pester them.
On the '96 Tracker (the first major-modified version of the J/E platform) the headlight relays are on a bracket mounted under the dash on the passenger side. You can see the bracket at the bottom edge of the dash kick panel. Maybe they are there...  Find the commonly colored wire that goes to BOTH relays and you found the wire that you want to tap into.
Now the circuitry:
The pic below puts a relay in the circuit so that the big current flows through the relay instead of the switch.ÂÂ

The pic looks better if you download it...
Hope this helps!