Sorry this is long but I've tried to cover the waterfront here.
Ric is right on the probability that the bushings in the motor gearbox
are shot. The website Ric referenced is great. Go slowly in loosening
the screws between the motor and the gearbox (so that you can tip the
motor and release pressure between the worm gear and the teeth on the
big nylon gear). Scrape off the black paint around the screw heads and
leave a drop of penetrating oil on each screw overnight -- saves
shearing the screws -- which would get you into another fussy repair.
(Post here if that happens and we can offer tips.)
Elecrical symptoms point to a ground problem between the ground terminal
on the left headlamp and its chassis connection. Following is based on
pages 100 and 102 from the '89 shop manual -- '90 should be similar
however there was a change in the harness connector between the frame
harness and the actual headlight units (I think this was to support the
higher wattage lamps that went into the '90).
There are separate grounds for the right and left headlights; however,
there's a tie wire between the two grounds. The broken or poor ground
is causing headlight and/or motor controller current to return through
the hi-beam indicator causing it to stay on.
If the hi-beam indicator is on only when the headlights (either hi or
low beam) are on, then the broken ground is between the left headlamp
and the headlight motor controller. (Trace between the connector on the
back of the headlamp, through the short harness on the headlight
assembly then through the connector between the assembly into the
harness to where the ground from the headlight motor control unit (small
black box in the left-forward of the engine compartment) connector
enters the harness. If the hi-beam light is on all the time (headlights
off or on) then the ground break is between the controller and the rest
of the stuff on that ground leg.
The stuff on that ground leg includes: Left engine compartment light, LH
Horn, LH Cornering Light & the headlight motor controller for both
headlight motors. If most of those things are working OK I'd put money
on the black wire close to the headlight or the actual connector to the
sealed beam itself. If that's not the case, your break is probably
buried inside a harness. In that case, the easiest fix will be to run a
ground wire from somewhere near the headlamp to a solid frame ground
point. (Unless you are a purist. If so, then it's harness repair--no
Hope this helps....
Happy SuperBowl results everyone!
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