Hello,

I have been battling a low voltage situation in my '89 780.
The main symptoms are dim headlights. When I turn on the headlights, the voltage drops visibly on the voltmeter.
With a normal voltage regulator, the voltage is in the low 13's when the lights are off and in the high 12's when they are on. I have Euro lights and I'm using standard 55/60W bulbs.
I have installed an adjustable voltage regulator, and that has helped a bit, but the voltage is still lower than the high-13's I'd like to see.
This weekend I pulled a 80A alternator from a 760, and installed it, made no difference whatsoever (except voltage is back to the above mentioned levels without the adjustable regulator).
I thought the system voltage is fully dependent on the alternator, but I wonder if there might be some other cause. I should also mention that I live in Fort Lauderdale, FL, so it is quite warm most of the year. I know that alternators are built to put out a higher voltage at cold temperatures and a lower one when it is hot - if this could be disabled somehow, maybe it'd help.
I know that I should install relays to power the headlights, and it is definitely in the plans, but regardless I'd like to cure this voltage problem.
I'd appreciate any suggestions!
Thanks,

Balu
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'89 780T, 223k mi; '80 245, 364k mi