I finished up on the relay pack I was working on, and one of the issues that spun out of it was that; YES - the headlights switched from bright to dim.

HOWEVER (God how I sometimes hate that word!):

There was no significant difference in the angle of the high beams to the low beams. They both pointed to the exact same target when we adjusted the lights...

The method is fairly simple. I start by adjusting one light at a time while covering the opposite light with a towel or other convenient object. The initial adjustment is to set the highbeams dead level with a point directly in line with the body of the vehicle, and at the same height as the headlight itself above the pavement.

The second adjustment is for low beams. The left one should be more or less straight ahead so that it is inside of a deviding line on a roadway - keeping it in the same lane as the vehicle so as not to blind oncoming traffic.

Guess what? There was no change in angle. These lights seem to be designed to point in the exact same direction whether on low or high.

What the heck is up with that???

All other dual-beam lights I am familiar with point down and to the right (in the USA) when switched to low beams....

I'll post the part number tomorrow.

 

The way you are supposed to do it is find a level parking area with a building adjacent to it. Drive the car up to the wall of the building as close as you can. The headlights in highbeam mode should make two spots on the wall. Mark these for vertical and horizontal, like cross-hairs in a scope.

Then back the car up 25 feet straight back, and adjust the highbeams to line up with the marks you made on the wall.

I would also check your wiring and make sure the lowbeams are the only filaments that are powered.

 

They are. I've done lights for 30 years, and never seen this come up before.

The low beam filaments each recieve 12 volts from the same relay.

Each high beam recieves 12 volts from it's own relay.

The center connection is the common ground and is tied to the cab by a ground not more than eight inches away.

Oh yeah - it's wired right. We ran every check in the book both installed and during the fitting phase, including wire code matching.

This is wierd. It ought to be the same bulb number as an 82 F100 according to A-Zone. I know the relays are switching, but I wonder if there is a hidden bug.