Headlight Question

[terbronco7]

Need some help, whenever I pull my headlight swith all lights work except head lamps, parking, tail all ok no headlights any idea? Has me at wits end.
As always thanks for the help.

[ianw31]

I had a similar problem my issue was with my horn relay also found that the connectors going to and from the relay needed to be cleaned up. Hope this helps

[ray_mcavoy]

There are a number of things that can prevent the headlights from working .... bad connections in the wiring (including bad grounds), failed dimmer switch, or a failed headlight switch are the most common.

Pull the headlight switch out all the way and use a test light or multimeter to see if you have power on the light blue wire at the dimmer switch. No power there means you have a bad connection somewhere between the headlight and dimmer switch or a failed headlight switch. A bad power feed to the headlight switch can probably be ruled out since you said the parking lights work. Edit: However, it is possible that a weak connection in the power feed could allow the parking lights (but not the headlights) to operate ... see below.

If you do have power on the light blue wire at the dimmer switch, check the tan and light green wires. Tan is low beam and lt. green is high beam ... one of them should have power. If not, you could have a bad dimmer switch or bad connection at the dimmer switch plug.

If the dimmer switch checks out okay, move on to testing the connectors out at the headlights. No power there means there is likely a bad connection at either one of the bulkhead connectors. There's one on the firewall and another where the headlight wiring passes through the radiator support. Finally, the headlights need to have good grounds. Each side should have it's own ground wire that runs from the headlight plug to a screw on the radiator support ... make sure those connections are free of rust/corrosion and the screws are tight.

Edit: I just noticed what Ian posted at the same time. On 63-66 trucks, the screw terminals on the horn relay serve as a BATT+ distribution point. So I can see where a weak connection there could allow some of the lower current loads to still operate okay but cause problems when higher current loads such as the headlights are switched on.

[terbronco7]

Originally Posted by ray_mcavoy

There are a number of things that can prevent the headlights from working .... bad connections in the wiring (including bad grounds), failed dimmer switch, or a failed headlight switch are the most common.

Pull the headlight switch out all the way and use a test light or multimeter to see if you have power on the light blue wire at the dimmer switch. No power there means you have a bad connection somewhere between the headlight and dimmer switch or a failed headlight switch. A bad power feed to the headlight switch can probably be ruled out since you said the parking lights work. Edit: However, it is possible that a weak connection in the power feed could allow the parking lights (but not the headlights) to operate ... see below.

If you do have power on the light blue wire at the dimmer switch, check the tan and light green wires. Tan is low beam and lt. green is high beam ... one of them should have power. If not, you could have a bad dimmer switch or bad connection at the dimmer switch plug.

If the dimmer switch checks out okay, move on to testing the connectors out at the headlights. No power there means there is likely a bad connection at either one of the bulkhead connectors. There's one on the firewall and another where the headlight wiring passes through the radiator support. Finally, the headlights need to have good grounds. Each side should have it's own ground wire that runs from the headlight plug to a screw on the radiator support ... make sure those connections are free of rust/corrosion and the screws are tight.

Edit: I just noticed what Ian posted at the same time. On 63-66 trucks, the screw terminals on the horn relay serve as a BATT+ distribution point. So I can see where a weak connection there could allow some of the lower current loads to still operate okay but cause problems when higher current loads such as the headlights are switched on.

Thanks, the weird thing is they worked fine day before yesterday then they just stopped. I will check out everything and report on my progress. You guys are the best!

[NEWFISHER]

I'm betting corrosion a the floor mounted high beam switch. You accidently, without knowing, brushed your foot onto it and "switched" it. The corrosion is preventing voltage to reach the lamps allowing everything else to work. Kick the switch and see what happens.

[Clyde65]

I think your parking lights and your headlight wires are swapped at your headlight switch. but it also could be what these guys are saying too.

[kieth]

After you figure out the problem and get your headlights working, do your self a favor and install relays to operate your headlights. This will eliminate the high voltage draw thru the headlight switch and provide lots of nice clean high amperage power to your starved headlights. You will get lots brighter headlights without installing new headlight bulbs. Check around for various threads on this forum that explain how to do this.

ps as a afterthought I soldered a ground wire to each lamp housing on my truck and grounded them through a common ground block at the front and the rear of my 66. all of the lights are brighter stop, turn, taillights, backups etc....grounding through a old rusted light to body housing is just unreliable and inefficient. Kieth Lowest cost lighting upgrade one can do .......

[jtrichard]

ditto newfisher first place I would look is dimmer switch