Check your grounding straps from the engine to the chassis. I suspect an intermittent ground problem, causing the engine to become isolated from the body wiring, which causes a spike in the alternator volatge output (it doesn't 'see' the battery, so the volts go shooting up).
While you are poking around the engine compartment, make sure your motor mounts haven't given up the ghost, allowing the engine to rock around and take out your grounding straps.
If you can, find out what the voltage does, both at the battery and on the engine, when you play with the lights and the engine revs. This will help confirm my guesstimate or show me to be full of it!
Brian