Another Headlight/Wiring help thread

[77RHINO]

I've got a question for the wiring gurus: For as long as I've had the bronco, only one low beam headlight worked, but they both worked on hi-beam, so I just drove it that way (I rarely drive it at night). This past week I put in a new dimmer switch, headlight switch, and nightlighter harness from WH. Now, when I pull the headlight switch out to the first click, park and headlights come on. They stay the same when I pull it out to the 2nd click on the switch, but kill to just the parking lights as soon as I hit Hi-Beam. The hi beam indicator will come on, all dash lights work, but no headlights, just parking lights. I have put new grounds at all 4 corners, and can't figure this out.

Also, only the drivers rear sidemarker works, even though I just put new bulbs in all and they all have worked in the past.

On a brighter ;D note, I did fix my reverse lights that have not worked since I've owned the bronco. PO clipped the wire inside the taillight corner which I discovered while working on the grounds.

What are yall's thoughts?

 

[SHX669]

How old is the headlight switch ? Wouldn't hurt to replace it and at the same time install a 'headlight relay " setup that one of the vendors sell . If that doesn't fix it then you have at least eliminated those from the suspects and both are certainly improvements especially if your headlight switch hasn't been replaced.

 

[77RHINO]

Those are the parts I installed last week in hopes to fix this issue. I re-did the grounds on the taillights, fixed the grounds on the two front parking light buckets, installed a new dimmer switch, headlight switch, and night lighter harness. Thats where I am confused is how both low beams all of a sudden work, but no hi beams, and then all but one of my side markers going out?

 

[Skiddy]

I would double check the wires at the headlights. mine did something similar and I had two of the wires switched at the headlight

 

[77RHINO]

I don't have the actual plastic plug housings that were on there originally, only the wires/spade connectors. Can someone tell me which colored wires belong to which spade connector on the headlight? Or point me in the direction of a 77 diagram for that? My searches popped up older threads with pictures that were no longer active. I'm hesitant to switch them around testing and screw up my new parts.

 

[Skiddy]

I don't have the actual plastic plug housings that were on there originally, only the wires/spade connectors. Can someone tell me which colored wires belong to which spade connector on the headlight? Or point me in the direction of a 77 diagram for that? My searches popped up older threads with pictures that were no longer active. I'm hesitant to switch them around testing and screw up my new parts.

exact same thing as mine was, i'll find the thread in a sec

 

[Skiddy]

exact same thing as mine was, i'll find the thread in a sec

here you go, hope it fixes it
http://classicbroncos.com/forums/showthread.php?t=274492

 

[77RHINO]

Thank you Skiddy! I will check it and let ya'll know how it goes!

 

[77RHINO]

Alright, I have figured out some more to this. I cut back some tape in the wiring and found an additional ground wire that grounded out the drivers sidemarker light, which now works. I also fiddled with the passenger rear sidemarker housing and got it working. The big question is the passenger front side marker. If I pull that bulb out, the headlights do not work at all, only parking lights, in any setting of the headlight switch.

What does this mean?

 

[Viperwolf1]

Alright, I have figured out some more to this. I cut back some tape in the wiring and found an additional ground wire that grounded out the drivers sidemarker light, which now works. I also fiddled with the passenger rear sidemarker housing and got it working. The big question is the passenger front side marker. If I pull that bulb out, the headlights do not work at all, only parking lights, in any setting of the headlight switch.

What does this mean?

It means that headlight doesn't have a ground.

 

[DirtDonk]

And even if it does physically have a wire running to the core support sheet metal, it might still not be grounded.
You can test that theory by temporarily running a jumper wire from the battery negative to the headlight ground screw/stud there on the core support. Maybe run to both of them (even if that shouldn't make a difference) just in case.
If your headlights work at that point, you'll need to make that temporary ground wire a permanent one.

Do you have a main ground wire from the battery negative to the body anywhere?
The original one from Ford did, but most people overlook that when changing out the negative battery cable.

Paul

 

[77RHINO]

Thank yall, that got it fixed! Another missing ground and a bad headlight. With that ground fixed, then only one headlight worked on low beam, and both on hi, so I swapped headlights and they all came on! That makes 3 clipped or missing wires I have found from the PO. I have grounds from battery to block, and then ground straps running from that bolt on the block to the frame and to the core support. I do have one parking light a bit brighter than the other but I am going to go through the sockets and clean up/paint the inner housings and hope that will take care of it. Thank you again for the help, its on to the next problem!

Ryan