Highbeams work but wont stay in the On position
 

So I've been driving my car all over the place after taking 3 years to get it on the road. Was doing a really nice back road cruise one night and before heading out my highbeams would always click on when I pulled the stick back untill it clicked in place. Now I pull the stick back and the highbeams will still flash but the switch wont stay in the highbeam position, once I let go of the switch it just defaults back to low beams.

Is this common? Do I just need a new switch?

I have an 89 GTU

If you hold the switch back do they flash from high to low continuously until you let the switch go? i had this problem and it turned out to be a bad connection at the retractor fuse in the main fuse block. My headlights where stuck in the up position too. Fixed the loose connection and the retractors started working and the highbeams worked also.

Bad latching circuit in the Dimmer Switch. Get another.

You can prove it by going to the Dimmer Relay and putting a constant ground on the white wire in the relay base. If the headlights stay on high all the time, then the Switch is bad.

Or I had this problem with my car, one of the plastic threaded bit that the screw that holds the switch goes into had broken. Made it alot more difficult for the switch to lock into place

No if I hold the switch back the high beams stay on as long as I hold it, once I let go it goes back to low beams