Tested the headlights with a ground and hot wire. lights on.
Power is not making it forward the firewall. Is it possible Year One sent me a defective switch? Any way to test the theory?
Does the headlight/parking light/dimmer switch need to be grounded?
Sounds like it was a coincidence that jumping the light switch at the connector made them work. Or, there is still a problem at the terminals at the light switch; corrosion or bad connection. Try wiggling the light switch connector.
Same with the dimmer switch. Like Firebob said, they are problematic, especially the terminals. They corrode and overheat. Try wiggling and/or cleaning the terminal contacts.
Also try jumping the terminals again at the new light switch to test/bypass the light switch to see if it's bad.
None of the switches need to be grounded to operate the headlights. (The light switch is grounded to operate the dome light.)
The only other connection is the firewall bulkhead connector below the master cylinder. I would check that last.
could there be a fuse problem? mine just quit at the store last night. tailgated someone home in the dark. i'll let you know what i find. already have a new switch on mine too
Besides checking the components I listed earlier, you can start at the Red? wire where power comes in to the headlight switch with a test light and work your way to the headlights.
I have attached a section from my 69 Camaro diagrams I drew that might help you. I'm not sure if the colors are the same as a Firebird, but should be very close. Close enough to guide you through the circuit.
Jumped the brown and brown/white wires at the connector. High's/ Low's all work. Except.. The firebird schematic shows it's the Lt Blue wire going to the high/low switch on the floor.??
The headlight switch should have an internal circuit breaker but if the tail lights work, I think the breaker will be OK.
I don't know the aftermarket harness you put in. On a stock 68 the red wire supplies power and the blue wire goes to the high low switch. If you jump the red and blue and the lights work then it has to be in the switch or connector. Disconnect the connector from the switch, use a volt meter to see if you have 12 volts at the red wire in the connector, if yes get a small wire and jump from the red terminal to the blue, if the lights work then you know everything is good from the connector out. If the lights don't work then the problem is from the connector downstream- the high low switch, the firewall connector block, headlight wires, sockets etc. With the headlight switch still disconnected put a jumper wire from the red terminal [if there is 12 volts there] to the spade that the red terminal mates to and see if you get 12 volts at the spade that the blue terminal connects to, if not the switch is faulty. You should be getting juice at the other spades as you said the tail and marker lights work.
I had trouble with the high-low switch, replaced it and still had trouble, it would work for a while if I really stomped on it. I had power going to the switch but not out, I bench tested the switch and it was good, the problem was the connector that the switch plugged into. I wired in a new connector and no longer had the lights go out in the middle of the night while trying to negotiate a sharp curve.
If you have o volts at the red your problem is not the switch. The switch can't power up the lights if there is no power going to it. Follow the red wire to the fuse panel and check the reason you have no voltage, I can't remember if the wire goes back to the terminal marked 'lamps' or not. The fuse panel terminal that the red light-switch wire goes to will be hot all the time whether the ignition switch is on or not. I don't remember if the headlight switch terminal in the fuse panel is fused or if it relies on the switch breaker and the fusible links for circuit protection. Sorry my car's not home tonight so I can't check it out for you.
The white is the courtesy/dome light circuit and is hot, when you open the doors the circuit is grounded and the lights come on or if you twist the headlight switch knob the circuit grounds and the lights come on. When you jumped white to blue the white circuit grounded through the headlights and the courtesy lights came on, there's not enough juice in the circuit to light up the headlights though.
I installed the M&H harness set in the '68 with zero issues. I used the original headlamp switch and a reproduction high beam switch.
The car is assembled to the point where getting voltages would be difficult at best, but one note, be sure you are getting a good ground on the headlamp switch in the dash as well as at the core support ground wires (both of them).
Do the tail lamps work as expected? Parking lamps?
Vikki
1969 Goldenrod Yellow / black 400 convertible numbers matching