Hi folks,
I thought I'd share what I found in troubleshooting and fixing the no brake light and no hazard light condition in my 1991 Laredo. This forum was invaluable in helping me find the issue, so here's me giving back.
The brake lights literally went out in front of my eyes as I was following my wife home a few days ago. Some poking revealed that the four way flashers were also out.
I checked the fuses, bulbs, and hazard flasher - all were fine, though there was some wear on the light bulb contacts. The brake switch was also fine, as was the turn signal assembly. Some troubleshooting with a voltmeter revealed that with the light bulbs removed and the brake pedal switch "on" I had 12 volts between brake light power and ground. With the light bulbs installed, I had 0 - ~0.04 volts. I checked all grounds and cleaned and tightened the body connections, with no luck.
Next, I disconnected the brake switch and fed 12 volts down the light side of the wiring harness. The brake lights lit up, which told me that the wiring and ground from the dashboard back was good. That meant the problem existed between the fusebox side of the brake switch and the battery.
I kept working towards the battery with my voltmeter and ohmmeter until I got to the power distribution box / fuse box by the battery. I again fed in 12 volts to the brake light side of the hazard/brake light fuse, and again got brake lights. Now the problem was between the box and the battery.
I tested for continuity between the battery side of the hazard/brake light fuse and the positive battery cable, and found a very high resistance present. It's then I discovered the problem - on this year Jeep, a separate wire provides power to the hazard/brake light fuse. The wire was corroded at the end that was clamped onto the positive battery connection. I pulled out all three wires (fuse box power, alternator feed, and the hazard/brake light feed), cleaned them up, and crimped and soldered a ring terminal to the hazard/brake light wire. I then reassembled everything, putting a battery cable clamp bolt through the ring terminal to hold it secure.
After that, everything worked fine. This whole process took me since Wednesday night, poking here and there. At one point I had two voltmeters running trying to figure out what was wrong. It was frustrating and counterintuitive many times, but my lovely wife kept me from setting the Jeep on fire and pushing it into the street
I hope this helps someone else - as I said, this forum helped me find the fix to my problem, so hopefully I can return the favor and help someone else.
-Ryan
I thought I'd share what I found in troubleshooting and fixing the no brake light and no hazard light condition in my 1991 Laredo. This forum was invaluable in helping me find the issue, so here's me giving back.
The brake lights literally went out in front of my eyes as I was following my wife home a few days ago. Some poking revealed that the four way flashers were also out.
I checked the fuses, bulbs, and hazard flasher - all were fine, though there was some wear on the light bulb contacts. The brake switch was also fine, as was the turn signal assembly. Some troubleshooting with a voltmeter revealed that with the light bulbs removed and the brake pedal switch "on" I had 12 volts between brake light power and ground. With the light bulbs installed, I had 0 - ~0.04 volts. I checked all grounds and cleaned and tightened the body connections, with no luck.
Next, I disconnected the brake switch and fed 12 volts down the light side of the wiring harness. The brake lights lit up, which told me that the wiring and ground from the dashboard back was good. That meant the problem existed between the fusebox side of the brake switch and the battery.
I kept working towards the battery with my voltmeter and ohmmeter until I got to the power distribution box / fuse box by the battery. I again fed in 12 volts to the brake light side of the hazard/brake light fuse, and again got brake lights. Now the problem was between the box and the battery.
I tested for continuity between the battery side of the hazard/brake light fuse and the positive battery cable, and found a very high resistance present. It's then I discovered the problem - on this year Jeep, a separate wire provides power to the hazard/brake light fuse. The wire was corroded at the end that was clamped onto the positive battery connection. I pulled out all three wires (fuse box power, alternator feed, and the hazard/brake light feed), cleaned them up, and crimped and soldered a ring terminal to the hazard/brake light wire. I then reassembled everything, putting a battery cable clamp bolt through the ring terminal to hold it secure.
After that, everything worked fine. This whole process took me since Wednesday night, poking here and there. At one point I had two voltmeters running trying to figure out what was wrong. It was frustrating and counterintuitive many times, but my lovely wife kept me from setting the Jeep on fire and pushing it into the street
I hope this helps someone else - as I said, this forum helped me find the fix to my problem, so hopefully I can return the favor and help someone else.
-Ryan
