The voltmeter in the 91S started reading a little low, maybe 13.5 volts instead of the normal 14.5, and at idle the needle would wobble a little until the engine is revved, returning to normal.
Tightened the serp belt and all is fine. I guess I let it get a little loose. I do like to run it not nearly as tight as the manual calls for in order to protect the water pump and serp idler. Maybe about 60-70 lb tension according to the Gates Kriket doohicky. I generally set it so that on a cold start with the a/c turned on, it may give just a little squeak for a second or two, then be ok. I don't normally run the a/c anyway around here, but once the belt is warm, all is ok with the a/c, no slipping as would be indicated by the voltmeter.
1989 Milano, Shankle Sport
1991 164S, stock
1994 164LS (~Q)
1972 Morgan 27
previously owned since 1964:
62 Morris MiniMinor 850, 67 Austin 1275 Cooper S (Downton 3/4 race), 64 Giulia Sprint GT (1st red one made), 72 Fiat 128 Sedan, 75 Alfetta Sedan, 78 Alfetta Sedan, 78 GTV, 81 GTV6, 86 GTV6