Headlight high to low beam problem

[adunham]

Just tying up some loose ends here. This one is headlight related. Turn on the headlights on low, only the driver's side comes on. Hit the footswitch for brights, the driver's side goes off and the passenger comes on (high). All four filaments are intact. Bad footswitch?

 

[SeaBiscuit68]

Sure sounds like a bad switch to me. Fortunately an inexpensive part.

 

[72_EB]

If it was just one side going on and off with the dimmer, I'd point the figure at a headlight, but with both sides, I'd blame a switch too. I'd start with the dimmer (cheaper and easier than the headlight switch) and more likely the problem.

 

[mountain14er]

I bougt a used wrangler with both taillights out so I was convinced it was wiring. Sure enough, both bulbs were cracked and the wiring was fine.

On the bronco, I thought the dimmer had three wires going to it, power in and hi/lo power out. I don't think a bad switch could make just one bulb come on. It could be wiring between the switch and the lights but bulbs are still a possibility.

 

[70_Steve]

It could not be the dimmer switch. That switch is only a single pole double throw switch. Headlight power in, and either high beam or low beam power out. It splits to each headlamp in the harness. Sounds like the problem is in the harness or at the headlamp plug.

 

[RangerRob]

Double check your grounds. Bad grounds can do what you are describing (along with other goofy stuff!). I assume this is with the original headlight wiring setup?

Good Luck!!!

 

[Skuzzlebutt]

Dual filament lights can do some screwy things when the grounds are bad so do check that.
Have you tested the wires at each lamp for power? That should have been your first step, before writing here.

 

[adunham]

Double check your grounds. Bad grounds can do what you are describing (along with other goofy stuff!). I assume this is with the original headlight wiring setup?

Good Luck!!!

No, its a Centech...

 

[70_Steve]

Does Centech provide a schematic of their harness??

If you look at a schematic of the stock wiring harness you'll see what I mean. The one low beam wire from the dimmer switch is spliced into two wires, one for each headlamp. The one highbeam wire from the dimmer switch is spliced into three wires. Two for the headlamps and one for the high beam indicator on the dash.

 

[DirtDonk]

Even with the Centech, if the grounds are to the grille shell or core support, they might not be grounding well enough to the rest of the body to keep things normal. It doesn't seem like this would be the case, but the last Centech install I did had this issue. But in this case both lights (as you would suspect) didn't work.
So because you've got alternating beams, it sounds like something else. But you never know about grounds, so I'd check that first. You can just turn the lights on and then use a jumper of some type to ground the grille shell and core support to the chassis to see if anything helps.

But first do what Skuzzlebutt suggested and check for power at the connectors (if you haven't already that is) and make sure it's not the bulbs even though you said the filaments were good. They can fool 'ya pretty quicl.

Good luck.

Paul

 

[adunham]

I'll be able to hit it with the multimeter on Wednesday, so the update on this issue is on its way. Thanks for suggestions so far...