I have a 65 hardtop. Recently purchased. The interior lights go on for a day, off the next day...back on in a few days, etc, etc. I looked over everything so far to no avail.
Is it a ground wire somewhere? This may be coincidental, but the winshield washer runs when I start the car, so I unplugged it.
Anyone have advice for me? I have also replaced all fuses in this car. Car starts and runs fine.

Have you replaced the door switches? Sounds like they may be sticking. Test them by pulling them out and see if your interior lights turn on and off by touching the two wires together.
Your windshield washer switch housing may need to be replaced or re-adjusted. It's plastic and they crack and don't work right-or work all the time or not at all.

Thanks for your response. I tried that exact idea with the door switches, but to no avail. It must be a ground problem somewhere? I have been all over this car checking wiring. I also have had problems with the dash guages(have replaced the voltage regulator for the guages) and still ALL of them are sporadic. I guess I'll keep looking for wiring issues, unless someone can give me further suggestions!

hello, Iam having problems with my dash lights on my 66 bird. I think my constant voltage unit is bad. Where did you get yours and how much was it?
As far as your problem goes, if all the lights are going out at once I would be looking at the interior light relay.
Don M.

Hey I think I've fixed the problem! I believe my pull-out headlight switch is bad. I can get them to come on most of the time by turning the dimmer function on my headlight switch. Groovy! Now to get a new one!
PS: the voltage regulator (behind the dash) didn't improve anything! I still have incorrect instruments.

Regarding the instrument gauge problem. On my 65 Tbird I replaced my oil sending unit the first time my oil guage stopped working. It didnt make a difference so must be the guage so i thought. Now my gas guage is acting up. It only reads that i have a quarter tank of gas all the time. Could it be my voltage regulator is faulty behind the dash? where can i get one of these? Does anyone have and ideas. thanks.