1987 911 Carrera Convertible

For the past several weeks, I have been having this problem where the headlights (and all interior lights) suddenly get brighter and dimmer. It is totally random, despite my best efforts to determine a cause and effect relationship. What's particularly odd is that the seatbelt warning lamp on the dash (above the radio) illuminates almost every time the lights go from dim to bright - then ater a few seconds, the warning light goes out. A few seconds later the process repeats. The battery is good, but I'm wondering if the voltage regulator or alternator mught be going bad. One night a few weeks ago, I switched to high beams and when the power surged, I blew out both headlights.

At real low RPMs, I have been able to make the battery warning light illuminate, but this has only happened a half dozen times in the pat 4 or so weeks.

THe one thing that does seem to make the power surge (i.e. seat belt warning light goes on and headlights and interior lights get brighter) is when I'm at a constant speed for a while and I lift of the gass just slightly. Doesn't happen every time but enough to notive a correlation.

Any thoughts would be appreciated.

Don

 

Don: Your symptoms are classic alternator/regulator failure. Some people attempt to just replace the regulator, but my shop always installed a rebuilt exchange unit which included a new regulator. Get it fixed before you have another high voltage spike and damage something very expensive!
Pete