I am having the same symptoms as described above in this post, namely:

Overvoltage, causing a headlight to blow (luckily everything thus far appears operational, but I've grounded the car)

Question: I replaced the voltage regulator about 6 months ago from one bought from fastlane, as I was having an "undervoltage problem" resulting in a dead battery.

That problem still occurs and a voltimeter confirms this: Voltage will swing between 12-18 volts, depending on driving..at freeway speeds, it went to 18 and I blew out both high beam headlights (yikes!)

Another faulty voltage regulator??? I plan to buy one from the dealer this time but could it be something else? Alternator=1 year old rebuilt from dealer. Starter about 5 years old.

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1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)