No tail lights and strange taillight behavior

[MikeTJ]

I'm doing a renovation on my 2003 TJ. While testing radio and backup camera before putting everything back I started getting some weird indications. First the Radio was "flashing" between night and day time brightness when the lights were turned. I disconnected the wire (orange) in the radio harness that senses that. But then I noticed I didn't have any tail lights and was having problems getting constant power to the rear camera. Turns out that with the key on and lights on I don't get any lights in the rear except a dim blinker (when they are turned on). All front lights seem to be working well. Fuses seem to ohm out okay. Hazard flashers flash in front and rear (but maybe a little dim in rear). Looking at the wire diagram it appears it all runs through the multi-function switch. I'm thinking about swapping that but wanted to hear opinions first.

 

[Chris]

Given the symptoms you're describing, the multi-function switch is a potential culprit. However, before you replace it I would check the following:

Ground Connections: Ensure all ground connections related to the lighting system are clean and tight. Corrosion can cause significant electrical issues.

Wiring Harness Inspection: Look for any visible damage, cuts, or frayed wires in the wiring harness, particularly around the rear lights.

Relay Checks: While less likely, check the relays related to the lighting system. A faulty relay can cause intermittent issues.

Bulb Testing: Although you mentioned dim rear blinkers, it's worth checking all bulbs for proper function. A weak bulb can sometimes cause unexpected electrical behavior.

 

[MikeTJ]

Given the symptoms you're describing, the multi-function switch is a potential culprit. However, before you replace it I would check the following:

Ground Connections: Ensure all ground connections related to the lighting system are clean and tight. Corrosion can cause significant electrical issues.

Wiring Harness Inspection: Look for any visible damage, cuts, or frayed wires in the wiring harness, particularly around the rear lights.

Relay Checks: While less likely, check the relays related to the lighting system. A faulty relay can cause intermittent issues.

Bulb Testing: Although you mentioned dim rear blinkers, it's worth checking all bulbs for proper function. A weak bulb can sometimes cause unexpected electrical behavior.

Thanks for the reply. I have replaced the multifunction switch (and the relay on it). Replaced the bulbs. Checked for corrosion. Checked fuses. Cursory check of grounds but not sure I found them all. A couple of more indicators. Brakes and reverse lights work with the headlights turned off but when you turn them on, the brakes and reverse lights stop working. Also, the blinker flash in the back but it's a fast flash like it has a short. However, the emergency flashers flash at normal speed with the lights on or off.

 

[Chris]

Thanks for the reply. I have replaced the multifunction switch (and the relay on it). Replaced the bulbs. Checked for corrosion. Checked fuses. Cursory check of grounds but not sure I found them all. A couple of more indicators. Brakes and reverse lights work with the headlights turned off but when you turn them on, the brakes and reverse lights stop working. Also, the blinker flash in the back but it's a fast flash like it has a short. However, the emergency flashers flash at normal speed with the lights on or off.

Not to be obtuse, but I assume you don't have any LED lights on the TJ?

 

[MikeTJ]

After I posted this I found the issue. At the risk of looking like an idiot, I'm going to post the solution so others might benefit from it in the future. Bottom line was that my tail lights weren't bolted onto the jeep, they were just sitting in the tub because I was prepping for paint. The lights get their ground from the mounting bolts screwing into the body of the jeep. Once I put one of those bolts back in it all started working right.