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Date registered: Nov 2002
Vehicle: 2003 G500, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
Mentioned: 6 Post(s)
Quoted: 96 Post(s)
It has been my experience that fresh electrolytic capacitors tend to be fairly tolerant of brief periods of over voltage, but they tend to go bang when even lower than rated working voltage is applied in reverse. Well aged, dried out caps (alas, like most in our W124s) can fail at the slightest provocation. Keep in mind that the OVP protects only those components it powers - the EDS and the ABS from over/reverse voltage, so any of the other electronics in the car like the CCU or tach may have been damaged by a voltage spike or momentary reverse voltage during the jump. Given this and the functioning A/C, it is certainly more likely that the tach itself is the problem, but I would still try to check for the tach signal and/or EDS codes before I replaced it.
Floobydust: a contemporary term derived from the archaic Latin miscellaneous, whose disputed history probably springs from Greek origins (influenced, of course by Egyptian linguists) - meaning here "a mixed bag." - National Semiconductor Audio Handbook