All 4 headlights went out at once

[rwljpl]

This group has been a great help over the years, really shortening my learning curve
Hopefully this issue has a simple fix
Got in the truck to run a quick errand tonight
Cranked it up but when I tuned on the lights the headlights did not come on
All 4 are out
Tail lights still work
Dash lights work
What would cause all 4 headlights to stop working at once?
All bulbs are pretty new
I checked fuses under the dash - the labels are not legible but all the fuses are good
Where should I start trouble shooting?
Is there ground wire just for the headlights that might have come loose? Where is it?
Something else I should check?

 

[Rickf]

Bad grounds or bad switch. Pull the headlight sockets then test the bulbs and sockets for power.

 

[rwljpl]

Would tail lights work if the switch was bad?

 

[Snoots]

Would tail lights work if the switch was bad?

Yes. Different circuit.

 

[SirRobyn0]

I'm going to echo what everyone else has said. Tail lights are on a separate circuit, so they can work even in the event of a failed switch.

What I would do is take one bulb out, test it for power at the plug, if there is power, it's got to be a ground. If there is no power go to the high low switch and see if there is power there, if there is power at the high low switch, but not at the headlight connector then it's got to be the high low switch. If there is no power at the high low switch then you know it's the headlight switch.

If I was to take a stab in the dark having never seen the truck before I'd bet on it being the headlight switch as most likely, the high changer second and the ground last, but you should run tests to diagnose it, before changing parts.

 

[Matt69olds]

Does the high beam indicator in the dash work?

Check for power at the headlight dimmer switch with the headlights on. It’s either a blue or yellow wire, depending on the year. I don’t recall when GM changed the color. There will be a tan wire (low beam) and a light green wire (high beam) whatever color wire is left is the headlight voltage source from the headlight switch. If you have no power, most likely the headlight switch is defective. If you have power there, check for power on the tan and light green wire. If you have no power three, replace the dimmer switch. If everything checks out, the problem is most likely under the hood.

Watch this.

xc_hide_links_from_guests_guests_error_hide_media

 

[SirRobyn0]

Does the high beam indicator in the dash work?

Check for power at the headlight dimmer switch with the headlights on. It’s either a blue or yellow wire, depending on the year. I don’t recall when GM changed the color. There will be a tan wire (low beam) and a light green wire (high beam) whatever color wire is left is the headlight voltage source from the headlight switch. If you have no power, most likely the headlight switch is defective. If you have power there, check for power on the tan and light green wire. If you have no power three, replace the dimmer switch. If everything checks out, the problem is most likely under the hood.

Watch this.

xc_hide_links_from_guests_guests_error_hide_media

That's an awesome video Matt!

@rwljpl your signature says your truck is an 1987, so it'll have the switch controlled by the turn signal lever, but it's the same thing really, the switch looks a little different and is located externally bolted to the side of the steering column down low, it is connected to the lever by a long link rod. Even the wiring is the same so the info in the video will translate directly to the column mounted switch.

 

[PrairieDrifter]

I'll bet the headlight switch burnt up, especially if you don't have a headlight relay harness.

 

[rwljpl]

Does the high beam indicator in the dash work?

Check for power at the headlight dimmer switch with the headlights on. It’s either a blue or yellow wire, depending on the year. I don’t recall when GM changed the color. There will be a tan wire (low beam) and a light green wire (high beam) whatever color wire is left is the headlight voltage source from the headlight switch. If you have no power, most likely the headlight switch is defective. If you have power there, check for power on the tan and light green wire. If you have no power three, replace the dimmer switch. If everything checks out, the problem is most likely under the hood.

Watch this.

xc_hide_links_from_guests_guests_error_hide_media

Thanks Matt
The high beam indicator on the dash does not work
When I move the stalk to go from to low beams there is no click as there normally would be
What does that tell me?
Thanks for the video - about to watch it

 

[Matt69olds]

I bet your going to find a defective dimmer switch.

 

[rwljpl]

Update:
Checked the grounds, everything was good
Replaced the headlight switch under the dash - still no headlights
Replaced the dimmer switch on the steering column - now I can get the dim lights to work, but I cannot get the brights to come on
What next? Getting that switch set up just right on the column is a little tricky, but I think I have it set up right, and even when I press dim/bright spring manually, it still only gives me the dim lights
What am I missing? What can I try?
Thanks for all the help

 

[Matt69olds]

Unplug the dimmer switch. Use a fused jumper wire and apply power to the green wire. If you still have no high beams, the problem is somewhere between the dimmer switch and the headlights. If the high beam indicator in the dash doesn’t work, that narrows the problem to between the dimmer switch and the firewall connector behind the fuse box. If the high beam indicator DOES come on, the problem is under the hood somewhere.

 

[rwljpl]

Got the headlights working agin
Thanks for all the help!

 

[nolv4ho]

How did you get the dimmer switch replaced? There's no room up there. Did you have to pull out the dash, or drop the steering column?

 

[SirRobyn0]

How did you get the dimmer switch replaced? There's no room up there. Did you have to pull out the dash, or drop the steering column?

I'm sorry I had in my head that we were talking about the dash dimmer not the high / low changer IDK why I guess I just lost track of the conv. Sorry about that.

If it's floor mounted see the next post from @wanderinthru if it's column mounted then it's tight. Drop the column down some while still leaving everything hooked up will work.