Electrical Headlight Issues (1 Viewer)

[AYM707]

I was trying re-arrange the wiring of my lights and managed to burn the fuse for the parking lights / turning signals. Replaced the fuse (20 amp) and everything is working except my headlights (LED). Horn works too (horn & headlights are on a separate circuit to parking lights / turning signals). I checked all other fuses and everything else is working. LED headlights did work before I messed with it.

There is no power in both headlight connections. I suspected my switch, so replaced it with a working unit and still no luck. I'm stuck and dont really know what to do. I need to take it for inspection on Sat. so appreciate some good ideas.

 

[John McVicker]

By happenstance could you have blown both of you headlight bulbs?

 

[45Dougal]

I was trying re-arrange the wiring of my lights and managed to burn the fuse for the parking lights / turning signals. Replaced the fuse (20 amp) and everything is working except my headlights (LED). Horn works too (horn & headlights are on a separate circuit to parking lights / turning signals). I checked all other fuses and everything else is working. LED headlights did work before I messed with it.

There is no power in both headlight connections. I suspected my switch, so replaced it with a working unit and still no luck. I'm stuck and dont really know what to do. I need to take it for inspection on Sat. so appreciate some good ideas.

How about high beam?
Try switching high- low a few times to clear the switch out.
Headlights have their own fuse - you sure that you have 12V on both sides of it?

Don't rely on appearance - the fuse is often broken or corroded

 

[AYM707]

By happenstance could you have blown both of you headlight bulbs?

I hope not; they are LED bulbs...not sure if i can replace them...

but there is no power in the incoming connector.

 

[AYM707]

How about high beam?
Try switching high- low a few times to clear the switch out.
Headlights have their own fuse - you sure that you have 12V on both sides of it?

Don't rely on appearance - the fuse is often broken or corroded

Both low and high beam are out. toggled it a few times. checked the fuses with a tester and all are good.

 

[pb4ugo]

Does your led headlights have a separate wiring harness? If it does it may have fuses incorporated in the harness. I know the Toyota halogen kit has a separate harness and has 2 fuses and relays.

 

[45Dougal]

Unplug the steering wheel connector and check for corrosion.
You can check for power at that connector from the headlight switch too (with the switch turned on).

(Red or Red-White should have 12V when the headlight switch is on)

 

[73FJ40]

What year truck? Hi/lo beam switch on directional or floor?

Once again, OP's need to better identify what year and what mods they have.

For all we know, it's a 1965 with a GM tilting column...

 

[kerplunk]

Pretty sure on mine, headlights are on a separate fuse. Headlights, horn and marker / parking lights are on three different fuses?

If you've already been replacing the switch, did you test for power at the switch on the plug?

Test for power at the hi/lo switch plug (with lights on)?

 

[AYM707]

What year truck? Hi/lo beam switch on directional or floor?

Once again, OP's need to better identify what year and what mods they have.

For all we know, it's a 1965 with a GM tilting column...

To clarify; its a 1982 FJ-40LV-KC GCC specifications. Only technical modifications are LED headlights, rest is stock.

Using a multimeter to check for continuity; I checked the female side of the head light connector, which comes from the battery / fuse box, & switch. Image below is reference

If I have one multimeter lead on the body (ie confirmed ground) both A & B are continuous; ie there are no breaks in their individual circuits. This confirms there is no issue with the switch, fuse, and internal wiring of circuits A & B. But if I connect the multimeter grounded lead in the G connector (ie ground), then no signal. I am assuming that means its a grounding issue?

Then I rigged up a spare LED bulb as a tester. I checked it with the battery...and it works. But if I stick a lead into A or B with the other on confirmed ground, nothing!! If circuits A & B are continuous; ie no breaks, the LED bulb should light up with a confirmed ground.

I also tested the LED headlights for continuity, connecting G&A and G&B which produces no sound; so does mean I should assume the LED headlights circuits are gone?

Horn, parking light, turning signals, plate light, and break lights all work. Appreciate some help / ideas.

 

[45Dougal]

To clarify; its a 1982 FJ-40LV-KC GCC specifications. Only technical modifications are LED headlights, rest is stock.

Using a multimeter to check for continuity; I checked the female side of the head light connector, which comes from the battery / fuse box, & switch. Image below is reference

View attachment 3422982

If I have one multimeter lead on the body (ie confirmed ground) both A & B are continuous; ie there are no breaks in their individual circuits. This confirms there is no issue with the switch, fuse, and internal wiring of circuits A & B. But if I connect the multimeter grounded lead in the G connector (ie ground), then no signal. I am assuming that means its a grounding issue?

Then I rigged up a spare LED bulb as a tester. I checked it with the battery...and it works. But if I stick a lead into A or B with the other on confirmed ground, nothing!! If circuits A & B are continuous; ie no breaks, the LED bulb should light up with a confirmed ground.

I also tested the LED headlights for continuity, connecting G&A and G&B which produces no sound; so does mean I should assume the LED headlights circuits are gone?

Horn, parking light, turning signals, plate light, and break lights all work. Appreciate some help / ideas.

So you've unplugged the headlight connector from one side and tested continuity to ground?
The two feed wires will normally show continuity to ground if the other headlight is still connected (which sounds like what you're seeing).

You aren't finding any volts on those connectors though so there is a break in the feed continuity somewhere. You need to find where the break is.

As I suggested before, check for volts at the steering wheel switch connector (the red and red white wire from the headlight switch).
You can also test continuity from this connector through to the headlight to prove it is connected.


I suspect your issue is much closer to the fuse box

 

[73FJ40]

LED = Light Emitting Diode.

To test an LED bulb, simply set your multimeter to the diode mode and touch the probes to the LED’s terminals–if it lights up, you know it’s working.

 

[AYM707]

LED = Light Emitting Diode.

To test an LED bulb, simply set your multimeter to the diode mode and touch the probes to the LED’s terminals–if it lights up, you know it’s working.

On my multimeter, the diode & continuity modes are the same. On the LED headlight side, tested both G&A and G&B connections and got nothing. Switched the probes but still nothing.

While testing for continuity, I noticed the resistor located above the wire ignition coil was extremely hot. Did a continuity test and there was no sound. I had a spare unit, so I switched it both the resistor and the coil. Re-tested the old resistor later & it appeared ok??!! So that was a bit confusing / frustrating. With the new resistor & coil installed; still no success.

I pulled the connector at the steering wheel, as suggested by @45Dougal and tested for continuity. There are 6 male connectors in that connector. I tested it against the outgoing wire at the fuse box (for the lights) and all provided a continuity signal. I am not sure what / how you would test for voltage...assuming one probe should be at the outgoing connection at the fuse and the other should be touching the red wire connector? Trying to understand where my voltmeter probes should be connected?

Was thinking to pull the voltage regulator from my FJ45 and see if it works here. Wiring connectors appear to be the same. But I dont want to screw it and end up with another problem.

 

[45Dougal]

Black wire goes to any good ground.
Red wire goes to whatever you want to test.

When you switch on the headlight switch, you should get power to both the red-white wire and the red wire.

The continuity test function is often very misleading due to the range of what is considered "connected" on your meter.

Testing for volts will tell you if there is a power feed or not.

 

[h82crash]

Black wire goes to any good ground.
Red wire goes to whatever you want to test.

When you switch on the headlight switch, you should get power to both the red-white wire and the red wire.

The continuity test function is often very misleading due to the range of what is considered "connected" on your meter.

Testing for volts will tell you if there is a power feed or not.

Yup. Testing for continuity only gives you good information if you know exactly how the circuit is run and you have isolated it.

 

[AYM707]

SUCCESS!!!

Was super frustrated, but went back to basics. Pulled every fuse out of the fuse box and checked the fuse again...and that's it!!! Just needed to be pulled and re-inserted back.

Thank you @45Dougal and @73FJ40 for your support and guidance.

 

[h82crash]

SUCCESS!!!

Was super frustrated, but went back to basics. Pulled every fuse out of the fuse box and checked the fuse again...and that's it!!! Just needed to be pulled and re-inserted back.

Thank you @45Dougal and @73FJ40 for your support and guidance.

Great! It would be a good idea to pull the fuse block and clean it. I had to do that and my dash switches. A soak in 30% vinegar for a few minutes and a soft wire brush will do the trick.