The battery went dead on my 1983 380SL, so I replaced the seven year old battery and checked the charging sysytem, as best I could with tools available (digital voltmeter). I was distressed to see only battery voltage at idle, with no change when I revved the engine to 3000RPM. I checked to see if the battery light in the dash worked in the #2 position, which it did, so I performed the only crude test I could think of, taking off the alt belt to see if the batt light would come on when I started it, which it did. This shows the warning system is working. On GM vehicles, I routinely see 14-14.5 volts at the battery at idle, even on a charged battery. Any ideas?

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1983 380SL
1995 C280
1995 S500 coupe
1990 Mazda Miata
2004 Suzuki Hayabusa