Wiring Headlight issues

[Petescj]

Having issues getting my headlights operating again. My floors get pretty hot by the hi beam switch cause my headers run right under there. I found the wiring was burned along with the switch itself. Ordered a replacement that said it fits my application. That's the black one in the pic. 3 wires nt 4 like my harness. Wired it up had lights for about 30 seconds then nothing. Cleaned and sanded floor for good contact and same thing.


The bottom one is out of another Cj. This has six wires. I dot know what to do with that. I'd like to use it cause it has better insulation than the to one. Below is what I have in the Jeep, 4 wires. What the he'll is going on. I cannot find a 4 wire replacement online. I just wanna take it to work but it's dark on y ride in. The weather is perfect right now.

 

[TSB8C]

The CJ uses a 3-wire dimmer switch mounted on the floor. So the black harness in your first pic is the stock setup. Not sure why your harness has 4 wires or what that black wrapped "bundle" is in that pic. The dimmer switch itself has 3 pins to connect into that black connector. There is no ground connection on the dimmer switch. So no concern with connecting the housing of the switch to the floorboard for any grounding need. When you turn on the headlights using the dash switch, the +12V goes from that switch to the center pin in the dimmer switch connector. The dimmer switch then routes that voltage out the left or the right pins (depending on low or high beam selection) to the headlights. So all you're doing is switching the +12V through that dimmer switch. The full current draw of your headlights is going through that switch, the connector, and the associated harness. For the most part, stock headlights are 35 watts for low beam and 55 watts for high beam. So that's 2.92 or 3 amps for low beams and 4.58 or 5 amps for high beams (times two since two lights wired together). So either 6 or 10 amps which could challenge old wires, connectors, etc. And if the headlights have been changed to something not stock (halogen or something), then the current draw could be even higher. So burning this switch and/or the connector is quite common in old CJs.

The answer is to re-route that power through an alternate path instead of the stock harness/switch. You can buy some kits to do this, or you can do this for about $10 and some scrap wire. Get two 12V automotive relays mounted under the hood somewhere and re-route some wiring. You'll get brighter and more reliable headlights and stop burning through dimmer switches.

Of course you need to figure out what's up with your extra wires in your harness that aren't stock.

Here's a thread with details on how to do it in a stock setup: Headlight Wiring Mod

 

[Petescj]

The CJ uses a 3-wire dimmer switch mounted on the floor. So the black harness in your first pic is the stock setup. Not sure why your harness has 4 wires or what that black wrapped "bundle" is in that pic. The dimmer switch itself has 3 pins to connect into that black connector. There is no ground connection on the dimmer switch. So no concern with connecting the housing of the switch to the floorboard for any grounding need. When you turn on the headlights using the dash switch, the +12V goes from that switch to the center pin in the dimmer switch connector. The dimmer switch then routes that voltage out the left or the right pins (depending on low or high beam selection) to the headlights. So all you're doing is switching the +12V through that dimmer switch. The full current draw of your headlights is going through that switch, the connector, and the associated harness. For the most part, stock headlights are 35 watts for low beam and 55 watts for high beam. So that's 2.92 or 3 amps for low beams and 4.58 or 5 amps for high beams (times two since two lights wired together). So either 6 or 10 amps which but could challenge old wires, connectors, etc. And if the headlights have been changed to something not stock (halogen or something), then the current draw could be even higher. So burning this switch and/or the connector is quite common in old CJs.

The answer is to re-route that power through an alternate path instead of the stock harness/switch. You can buy some kits to do this, or you can do this for about $10 and some scrap wire. Get two 12V automotive relays mounted under the hood somewhere and re-route some wiring. You'll get brighter and more reliable headlights and stop burning through dimmer switches.

Of course you need to figure out what's up with your extra wires in your harness that aren't stock.

Here's a thread with details on how to do it in a stock setup: Headlight Wiring Mod

Ok I'll work with the 3 wire harness then. I did have a harness with relays on my Virginia Jeep and the lights were much brighter. Only thing that's confusing me now is the whole 30 seconds of working than nothing. Hopefully that won't be the case this time around.

 

[TSB8C]

Ok I'll work with the 3 wire harness then. I did have a harness with relays on my Virginia Jeep and the lights were much brighter. Only thing that's confusing me now is the whole 30 seconds of working than nothing. Hopefully that won't be the case this time around.

One thing that came to mind is that perhaps inside that black bundle you have maybe there's a heat sensitive self-resetting circuit breaker of some sort. Run for 30 secs drawing too much current, then trips and cuts off the juice. Wait for a bit for it to cool back down and it resets for another go. I'd cut that bundle open and see what's inside. I couldn't tell from your earlier pic, but how many wires come from the CJ's harness under the dash into that bundle before the 4 wires come out?

Something else comes to mind - what type of switch did you originally have? For your year/model it should be the 3-wire with the black connector in your original pic like this:



However, I have seen people use older model dimmer switches in newer CJs. The older ones looked like this:


Perhaps some prior owner modified the wiring to use an older style like this second one. And with the color wires in your earlier pic, they still don't match the older stock setup, but worth looking into. You can verify all this with a simple volt meter. With the wires all disconnected from any dimmer switch, and not touching each other or any metal (floorboard, etc), turn on the headlight switch in the dash and measure for +12V on those wires. The one with juice is the main one coming into the dimmer switch from the dash mounted headlight switch. Now switch to the resistance settings (ohms) and measure the other wires to ground, unplugging each headlight one at a time. With the headlights connected, you should get a reading showing the resistance through each headlight bulb. Unplugging the headlights would then stop the readings one at a time. Connect the headlights back up, turn on the headlight switch again, and then touch the earlier found power to the others one at a time and see which headlight turns on (high or low and which side). Then you'll know where each wire goes.

 

[jzak]

That's weird that the high-beam wires are melting. I've also got a AMC 258 i6 / 4.2l with the headers running under the driver side floor pan, and I've never had any problems. Maybe it shorted out?