Alternator/generator/regulator problems of the 2002 Mitsubishi Diamante

Headlights turn off for a split second while driving down the highway. It does this when the ac system kicks in. Lights on the inside of the vehicle dim as well. This happens at both idle and high rpm. A volt meter shows a large voltage spike for a short period of time. The voltage regulator is not responding fast enough to pick up the voltage. Have worked for over a year with Mitsubishi to attempt to get this resolved. Their mechanics at 2 dealerships say that the problem isn't normal until they don't figure out the problem. Then they come back and say it's normal. I have yet to see a car do this - especially with the lights turning off while driving down the highway. If the problem was "normal" they wouldn't have taken my car into the shop to investigate the problem in the first place -- why spend hours trying to find a bad wire if the problem is "normal". I feel this is a possible safety issue, and the Mitsubishi district manager refuses to authorize the service dept to replace my alt. Or battery to see if it will resolve the problem. This has happened since the first month I had my car, and continues to happen now that there is 20000 miles on the vehicle. Number of failures is hard to estimate since it is a constant issue every time the ac kicks in at night. Will put 180 assuming 15 times driving at night per month.