Sounds like the small red wire on the back of the alternator is intermittently shorting and/or breaking contact. The small wiring harness which runs from the grey plug on the driver's side firewall down under the intake manifold and crank to the oil press. and alternator sensors is likely at fault. I replaced this entire branch of the harness on my car with fresh wires running in conduit across the firewall and down the fender. Took about 2 hrs.