electrical problem

well there has been an intermittant problem with the left turn signal on my 84 caprice classic.
i'm at college and my dad is trying to fix it, so the details are a little sketchy but here goes.
he replaced the bulb with one that was identical (so he says) and the flasher worked, but it flashed slower on the left side. the right side was still fine.
he was driving it tonight and when he turned the headlights on, the turn signal stopped flashing.

i dont really know all the details, but as i understand the flasher system, it works off a specific resistance value. you cant put HD bulbs in a normal flasher relay and vice versa. why would the system stop working when the headlights come on only?

the bulb he put in is one that he found in the glove box in a napa box. i dont know where the bulb came from, as it was already there when i bought the car. he says its identical to the other bulbs, so i'll have to take his word for it.

thanks for any help.


:popcorn:
ive always wanted to use that