I have a 2002 Jeep Grand Cherokee No drive side break light when I het pedal with headlights on.
With the headlights off the Driver side break light works although it is dim, with the headlights on I get nothing. I changed the light sockets,checked the bulbs, and the fuses yet it is still the same result.
check them thar bulbs real close. sometimes a filament breaks and jumps to the secondary filament ,very clever them gremlins are!
If you have a trailer hitch and light kit installed, I would check there first. Aftermarket products can cause many faults. Also check any fog lamp or extra lamp or lighting kits that you may have. Spliced in radios and amps are also a big issue. One car I came across had the radio power wire hooked to the neutral safety switch! The problem most likely will be with the light switch itself. If you have a good quality voltmeter and know how to use it, test the headlight switch then work your way down to the wires. For easier access pull out the entire light switch assembly (it's a pain in the arse, but you may be replacing it anyway) and test the switch terminals. You may also find that it's burned or melted. In which case you'll need to check for melted wires and the possibility of a wiring harness failure or a voltage problem. There are several youtube videos out there that will help you through the step by step.
the tail lamp lens assm.
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