when i turn on the headlights or do a headlight flash, the radio stops for a while and the rpm tach flicks to zero then back to normal again.

when i got home, i tested it with a volt meter while engine is on. it registered 14+V, when engine is off, its 12.7V. So I guess my alternator is fine.

Mga guru, what could be the problem and the solution?
di ko alam kung san ok magpagawa when it comes to electrical. i'm from mandaluyong.

car is civic 96 vti. Thanks in advance.