This happened to me a few months ago when I first got my FJ, and it's resurfaced. When I turn the headlights on, I get 12v+ to all 3 terminals on the headlights.

The switch is good. high/low beam lever is good.

I reached up behind the dash last time this happened, and when I moved a wiring harness, the lights came back on. Worked for a few months, and all through Tellico, and died pulling out of a parking space!

Any ideas?

Due to the hacked up harness (although the headlight circuit looks untouched), I am going to re-wire the FJ with a Painless harness and GM column, but I don't have the $$ right now.

Any ideas where I should start looking?

You don't really say what the problem is, but I presume that your headlights either don't light or they are dim.
Start looking for a high impedance (high resistance) connection (a corroded or loose connection) somewhere in the circuit. Just because you have 12V doesn't tell you whether the circuit will pass the current that is required to run the lights. The fact that you have 12V on all three of the light lugs tells you that you have a bad ground, since one of the three connections goes to ground.

Oops, sorry.. the lights don't light at all.

would a ground that's bad suddenly read 12v+?? I would think it just wouldn't read.. That's what concerns me.. a wire that SHOULD be ground, being 12v+.

Unplug the back of the head light, with the light switch off, one of the terminals should be ground, if it is not the voltage is huunting the ground, that is it is running thru the filament and since the ground is gone it is just hanging out there.
electricity as my Dad taught me is like water, it has to flow to a ground, woithout the ground it is like a faucet turned off.
Butch

Originally posted by Eskimo
would a ground that's bad suddenly read 12v+?? I would think it just wouldn't read.. That's what concerns me.. a wire that SHOULD be ground, being 12v+.

The fact that the end of the ground wire at the bulb reads 12V means that the other end of the wire that should be grounded is "floating", which means that it is either disconnected or has a high impedance connection to ground. If it was actually grounded, it would read 0V.

The water analogy is a good one. Volts are like water pressure and amps is like the flow in gallons per minute. Having a high impedance bad connection is like having a plugged hose. You still have the same pressure in the hose (12V) but it doesn't flow (drip, drip, drip when it needs to be 1 gpm)