I have a 92 chevy pickup half ton 2wd with a 4.3L. Every time i hit a bump or sometimes when im sitting still the battery light will flash real quick and the volts will drop and the speedo will jump.

Tighten and clean the negative battery connections on the frame and motor. Also tighten and clean battery connections.

After checking and cleaning the battery points, check for lose wires on the alternator also.

i have the same problem/ turns out my starter wire had loosed at the starter end,, chevys seem to start just being CLOSE to a battery,, heheh (bad connections) but without a solid connection the alternator sometimes doesnt charge,,, also when I turn on headlights or heater fan,,my guage drops to 9,,, its almost impossible without making a specila tool to tigheten properly on the engine so down it comes,, clean terminals and tighten (this always makes me nervous,, broke many solinoids over tightening,, hence why it got loose ,,, so maybe its time to make a tool to hold a backer nut,, and give er a good one!

My problem was my exhaust manifold came apart from the pipe and wen ever it backfired it burnt the cable and it keep hittin the heat sheild i put the exhaust back on and taped up the wire and worked perfect

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