If your '78 has two alternator belts like my '83 then either your belts are very worn out, or most likely loose, and they need to be tightened. Push on the belts with your fingers, and see how much deflection you are getting. (Engine off, of course) I bet it is more than 3/4 of an inch.
-Larry

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D