I'll take a stab at this one and say that you are correct in assuming the headlight relay has a constant 12V source and is activated on the ground side.

This info is based on the pickup/amigo wiring diagram, which probably is not the same as the Trooper, but it might give you some ideas.

There are 2 10amp fuses (next to the headlight relay) that are for the high beams.

The circuits from those 2 fuses then go to the left/right high beam connector (or, headlights).

From the headlights low beam circuits, they run to the switch/stalk on the steering column THROUGH 2 other wiring connectors... those 2 "other" wiring connectors are located near the engine firewall on the L/R sides.

I would trace all those wires and insure that the connectors are cleaned with some "electrical cleaner" spray.

As you mentioned, it could be the switch/stalk also... do you hear the telltale "click" when you try to activate the high-beams? Sometimes it's just that the switch/stalk needs a good cleaning or the point contacts are worn.

On a 17 year old vehicle, I would start with the switch/stalk.

HTH
Van <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />