High beams work, headlights don’t.

[Funstuie]

Hey all

The high beam switch on the floor works. Headlight switch doesn’t work.

I have swapped out all headlights and I know they work.

Is there a relay? The headlight pull set is a bit rough.

What the normal cause of this?

[kidatheart]

What year truck? If the dimmer switch is on the floor, that could be the culprit. Could be the switch, or just a bad connection in the plug in. That's my opinion, but it's not worth much! good luck

[RustyPile]

We need more information to give detailed trouble shooting procedures. Be that as it may, here is a basic headlight circuit description.. Most models don't have factory installed headlight relays.. Fuses aren't used either... The headlight switch has a built-in circuit breaker.. Over the years, the breaker weakens, and trips for no reason and the only repair is switch replacement..

Power is fed to the switch, one wire goes from the switch to the dimmer switch common terminal.. Power leaves the dimmer switch through 2 wires.. Depending on the beams (hi or lo) selected by the dimmer switch, power is routed to the headlight bulbs. The two wires from the dimmer switch split near the back of the radiator support and go to each headlight.

Using a volt meter or test light, start at the headlight switch and follow the power path through the connections, checking for loose and or bad connections including grounds.. If you have power to the headlight switch but nothing coming out, check the plug connections first.. It's not uncommon for loose connections to develop, causing heat to develop on these connections causing plug failure. If all is well at the plug, the switch is probably bad..

[franken]

Cycle the dimmer switch about 10 times.

[hatzie]

Originally Posted by RustyPile

We need more information to give detailed trouble shooting procedures. Be that as it may, here is a basic headlight circuit description.. Most models don't have factory installed headlight relays.. Fuses aren't used either... The headlight switch has a built-in circuit breaker.. Over the years, the breaker weakens, and trips for no reason and the only repair is switch replacement..

Power is fed to the switch, one wire goes from the switch to the dimmer switch common terminal.. Power leaves the dimmer switch through 2 wires.. Depending on the beams (hi or lo) selected by the dimmer switch, power is routed to the headlight bulbs. The two wires from the dimmer switch split near the back of the radiator support and go to each headlight.

Using a volt meter or test light, start at the headlight switch and follow the power path through the connections, checking for loose and or bad connections including grounds.. If you have power to the headlight switch but nothing coming out, check the plug connections first.. It's not uncommon for loose connections to develop, causing heat to develop on these connections causing plug failure. If all is well at the plug, the switch is probably bad..

The OP description of the problem leaves a bit to be desired.

I can only assume the HI beams light but the Low beams do not... That is probably incorrect but my crystal ball is on the fritz.

The headlamps have a fusible link in the feedline not a fuse... usually at the starter BAT terminal. It can differ by model year. There's no mention of the model year or other pertinent information. Again I find my crystal ball insufficient to the task.

I can't recall a circuit breaker in the headlamp switch itself.
If the parking lamps light up there is power to the switch.
The dimmer is a single pole double throw switch. It has three connections. Power in from the headlamp switch, Low beam out, and HI beam out.

If the HI beams light and the Low beams do not, as his verbiage seems to imply, then the dimmer or the dimmer plug is suspect.

[Funstuie]

Hey all

Sorry for the vague initial post and no follow up.

It’s 76 C10 stepside, Scottsdale trim with a 350 engine.

New wiring harness installed and the high beams and low beams worked but Suddenly the low beams, as in when I pull the light switch on the dash the low beams don’t come on - park lights do come on though. When I step on the switch on the floor the high beams do come on.

I replaced the headlights and the same still happens

I’ve ordered a new floor dimmer switch and a new dash switch

[hatzie]

It's the dimmer or the dimmer plug.

You can take the headlamp switch back.

[Bandit130]

I had a similar situation happen a few weeks ago. Pulled headlight switch, no lights. Pressed dimmer switch, lights came on high and would cycle low to high with each press. Replaced dimmer switch, solved.