Headlight Question (1 Viewer)

[1977FJResto]

I searched the forum and didn't see anything covering what I'm experiencing. Working on a rebuild of a 1975 FJ40. Did a frame off and am at the point of checking lights and systems. So far so good but headlights are being strange. I have power to both left and right headlights at the bulb. Both low beams have power and, when switched, both high beams. I confirmed both grounds as well. The problem is when I plug in a bulb to either left or right the circuit loses all power.

 

[RevISK]

The answer is almost always ground issues.
Other than that, socket condition and fuse block condition. Then check the switch itself.

 

[1977FJResto]

The answer is almost always ground issues.
Other than that, socket condition and fuse block condition. Then check the switch itself.

I'm thinking that as well. So far I confirmed the ground using a miltimeter to check ohms and both are good at the bulb socket. I checked the connection at the column and the low beam (red/green wire) has 12v going into the connection but only 6.5 coming out. Going to keep checking all wires and grounds. Was hoping it was something someone had seen before. Strange to have power at the bulb connection and lose it from both sides when you plug in a bulb.

 

[RevISK]

I'm thinking that as well. So far I confirmed the ground using a miltimeter to check ohms and both are good at the bulb socket. I checked the connection at the column and the low beam (red/green wire) has 12v going into the connection but only 6.5 coming out. Going to keep checking all wires and grounds. Was hoping it was something someone had seen before. Strange to have power at the bulb connection and lose it from both sides when you plug in a bulb.

Well, it would seem there is a short. Again, likely due to a grounding issue somewhere. How do your fuses look? When the load is being placed on the system, bulb is inserted, it is too much for the 6.5v.

You said you did a frame off, how much attention did you give your wiring? Same harness?

I’m still betting on ground. Maybe paint is interfering or you’ve got some brittle wires.

 

[RevISK]

Do you have a wiring diagram for your year?

 

[1977FJResto]

Do you have a wiring diagram for your year?

Thank you for the replies and advice. I do have a wire diagram and it has helped. I check and replaced the fuse and cleaned the terminal. I have 12v+ on both sides of the fuse. It is the original harness and it has a SBC conversion from the 1980s. I had to clean up the harness from the conversion but overall it's in ok condition. The worst connectors are those coming out of the harness. The sun baked the connectors for blinkers and headlights and they are brittle. I verified the grounds on both harnesses leading to the plugs for the headlights and took the switch apart yesterday. Switch is smoother now but no corrosion to speak of. I'm going to pick up some contact cleaner and clean all the connections.

 

[Green Bean]

Bill:
Alternatively, Toyota sells an upgraded headlight kit with its own harness and relays. As long as you are having to tear into and diagnose all of the headlight wiring anyway, you may want to consider...

Builds - '78 Refreshtoration, what next?

Great find on an awesome condition 40! You're learning all the right stuff from some of the best LC gurus in the world here on Mudd. Keep plugging away at it, these TLCs love lots of TLC lol

forum.ih8mud.com

Good luck.

 

[1977FJResto]

Bill:
Alternatively, Toyota sells an upgraded headlight kit with its own harness and relays. As long as you are having to tear into and diagnose all of the headlight wiring anyway, you may want to consider...

Builds - '78 Refreshtoration, what next?

Great find on an awesome condition 40! You're learning all the right stuff from some of the best LC gurus in the world here on Mudd. Keep plugging away at it, these TLCs love lots of TLC lol

forum.ih8mud.com

Good luck.

I have been considering this. I would be the light is far better than halogen sealed beams.

 

[RevISK]

I would try directly wiring the socket/bulb first and start checking things off. I use a 12v tool battery to diagnose things. More portable and safer.

 

[3_puppies]

are you using the stock switch or a GM column switch?

 

[1977FJResto]

I cleaned the connectors from the dimmer switch and the headlights work. Thank you for the help. Now to figure out the non blinking blinkers.

 

[1977FJResto]

are you using the stock switch or a GM column switch?

It's a stock switch