My 98 T100 4x4 headlights quit working, have checked the 2 10 amp fuses are good, pulled the H/L relay works when powered up by the battery with jumpers. H/L come on when the relay is removed anda jumper wire is connected into the circuit. Looking for a wiring diagram to help me figure this out. THANKS in advance.

 

Sounds like a broken wire someplace. Pull the plugs on the back of the bulbs, and ohm the wires out to their ends.

With no function at all, it sounds like the ground wire to me. Check the ground from the battery to the body, and the body to the headlights first.
It may well also be the switch on the steering column. Pull the cover off, and check the switch carefully. A dirty contact, or connector, can cause this trouble. Check the FSM for the locations of the plugs, the switch operation and so forth.

Hope this is a little help...
Pat☺