I am going to try and replace fuses first but is there any reason why none of the interior lights work? No dash lights, no door lights, no opera lights and no glovebox light.
Headlights and driving lights/brakes work along with the signals.
Past posts discussed the light switch but does that cover everything?
There is a thread about finding shorts that should help.
The most common cause of no dash lights is mistaking the illumination wire at the radio for a ground. If you recently installed a new radio that’s a possibility
Someone in the past had a radio in the car but was missing when I got it.
I seem to remember the lights working at one point.
There are three wires I haven’t figured out yet.
One has a weird j hook on it, another has three wires (a yellow, blue and another blue) going into a connector with two wires exiting that are taped off, while the third is a two prong connector.
The headlight switch provides power for all of the interior lights. Easiest thing to check are the 2 fuses in the fuse box,
2.5 Amp fuse in the middle of the fuse box. Note this is powered On when the headlight switch is in the Parking or headlamp positions. Feeds power to the instrument panel cluster lights, ash tray light, tachometer light, radio light, transmission selector light
7.5 Amp fuse to the middle right. Note, this circuit is powered On in all 3 headlamp switch positions. Feeds power to turn signal switch to power brake light switch and horn.
The headlight switch contains the following slots:
B – Battery, input circuit 25
R - Rear Taillamps, output circuit 14
I - dash illumination (*rheostat controlled), output circuit 19 to fuse box 2.5 A fuse, feeds power to instrument panel cluster lights, ash tray light, tachometer light, radio light, transmission selector light
P - Front Parking lights,output circuit 11
H – Headlights, output circuit 15, note routes to the dimmer switch, the dimmer switch then wires to the hi/low beam headlights
A - Brake Switch power feed, output circuit 10/460. Note, this circuit is powered On in all 3 headlamp switch positions. Feeds power to turn signal switch to power brake light switch and horn.
D1 - Courtesy Lamp Fuse, output circuit 54 to fuse box 7.5 A fuse. Note, this circuit is powered On in all 3 headlamp switch positions. Feeds power to the dome, courtesy, map, glove box, trunk, clock and seat belt warning lights
D2 - Courtesy Lamps, output circuit 53, note feeds all instrument, both door courtesy lamp switches, C pillar lights
Disconnect the headlamp switch and place a multimeter in Ohms mode with one probe in the B slot and the other probe in the slot being tested. Verify the truth table probing all of the slots with the 3 various switch positions.
Below is a “truth table” between the B slot (battery) and the corresponding slots:
| Switch Position | R | I | P | H | A | D1 | D2 |
|---|---|---|---|---|---|---|---|
| Off | Off | Off | Off | Off | On | On | Off |
| Park | On | On* | On | Off | On | On | On |
| HD Lamp | On | On* | Off | On | On | On | On |
*When testing the I slot (dash illumination), and the switch in Park and Headlamp position, turn the headlight knob clockwise and counterclockwise to see if the resistance changes. Counterclockwise will increase in resistance (causing the dash lights to dim) and as you turn the headlamp knob clockwise, the resistance will decrease ( causing the dash lights to become brighter). Turn the knob all the way to the right to the detent position and the resistance should be at its lowest value.
Thank you. This is exactly what I was looking for.
Not quite. Turn signal switch gets its power from either a circuit breaker or an inline fuse. Horn gets its power from headlight switch or circuit breaker (all depending upon year).
Just want to clarify any possible confusion.
I’m talking about my 68 Standard
My bad, I should have written
Feeds power to turn signal switch "CONNECTOR" to power brake light switch and horn.
Yes the turn signals themselves are powered from two sources, an inline fuse under the dash from the Acc post of the ignition switch and the hazards are powered from a circuit breaker in the headlight switch.
Coach Jack
Good to know that fixing the light issue might fix the relay issue.
I did find that one of the plugs I was trying to figure out is actually the center speaker.
The other two are still unknown.
If the light switch is bad, what is the recommended replacement should I go with an electric headlight conversion?
An electric headlight conversion only replaces the headlight doors that are vacuum actuated to electric using something like electric motors from Ford Probes. There are a lot of articles on how to do this but it does require you to cutout, fabricate then replace the headlight brackets. If your headlight doors currently work, I personally wouldn’t do this mod but hey, its your car you can do anything you want.
I think you are asking about using a headlight relay kit that uses the headlight switch to trigger a relay. The relay itself carries the load to the headlights thus relieving the headlight switch’s amperage to the headlight circuit. This is a fairly straight forward mod and can be easily reversed. Using a headlight relay mod is really useful in cars that the headlight switch (or the multiswitch especially on the old Datsun 240/260/280z ) draws too much amperage. Other benefits of using the relay mod is that the lights will be brighter because there is relatively little loss in power as the relay is typically mounted near the headlights themselves and you can run halogen bulbs without fearing of burning up the switch or the old wires.
Coach Jack
I would use the kit from WCCC. I was asking because of the vacuum ports on the switch which I wouldn’t need after the conversion (I have a broken headlight bucket already that I bought a replacement)
When I pulled the center 2.5 amp fuse it fell apart so I thought I was going to be in luck, but there was no change after replacing it.
FYI: Headlights, Turn Signals and Brakes all work so I don’t think there’s anything wrong with the 7.5 amp fuse (even though the horn does not work)
The photo’s are the wires of what I haven’t figure out yet.
An FYI that the electric headlight conversion kit(replaces vacuum components) or headlight relay kit(upgrades headlight wiring near the grille area to accept newer brighter headlights) would not have any effect on interior lights not working or a faulty headlight switch. You don’t do any interior wiring when installing those kits.
I’d suggest cleaning contacts on your fuse box, replace corroded fuses and check ground connections in the dash area. Your problem is in the interior wiring of the car and neither of those kits change any interior items or wiring.
Pull each fuse and clean the contacts in the fuse box and either clean the fuses or replace them all. Next use a multimeter and check for voltage at the fuse clips (note only 1 side of the fuse clip will have power without the fuses plugged in). Also note that the 2.5 amp circuit will not be powered unless you have the headlight switch in the park or on position. Put the fuses in and verify power on the other side of the clips as well.
Lastly, what was the outcome of the headlight switch tests I outlined in the truth table?
Coach Jack
I understand, I mention it because if I have to replace the headlight switch (and I do the conversion) I might as well replace it with a switch without the vacuum ports.
I was trying the fuses first before having to pull the switch for testing.
I did try in both parking light and headlight positions.
