don't know what model you have but to me the varying lighting level is likely brushes (voltage regulator in a 420sel) in the altenator, a slipping belt but could also be a battery that is losing it's ability to hold a charge. maybe a combination.
i see autozone people going out to the lots and testing peoples charging system and i don't think they charge for that except a tip for the guy going out of his way.
based on mileage and age a voltage reg for a 420sel is cheap 20 bucks or so. belt is cheap and if the battery is a cheap kmart or ?? brand even a good battery is cheap compared to a tow.
but before you start throwing money at the car get someone to check the charging system. heater on, lites on etc: then fix what's wrong then decide on the other stuff.
1972 350sl Red/Blk 117k
1988 420sel charcoal/Blk 140k
1987 420sel gold/tan 128k
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