Sounds like you may be losing your voltage regulator. 16V is high on a 12V system. I think mine on my old Dodge MH maxs at 15.1 volts which I have been told is borderline.

You can take it by an auto parts place and most of them will check these for free looking for the sale.

An '87 is way out of my range of experience to be able to help much. Sorry.

I think a lot of the older alternators on these cars and maybe yours have an external voltage regulator and they are pretty simple to replace.

Maybe try a search on this topic at the bottom of the page. Or to see if your model and year have an external regulator you can always go tot he fastlane link at the top of this page, go to their online catalog and see if this part is listed.

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique