96 XJ here. I'm just finding two problems at once, and I'm trying to find out if they could be related, as they're both electrical. I just noticed my GEN light is coming on (dash alt meter is way down), and testing at the local parts store shows my alternator has a bad diode. At the same time, I'm seeing that my brake lights aren't coming on at all, while all other lights are on, but dim. This bad alt is a new issue, while the brake lights not working may have been going on for a while. It's been at least 6 mos since I checked my brake lights, so they could have gone out by themselves, one by one. I just don't know.

So I'm wondering...is my low elec. problem causing my brake lights not to come on?

Nowhere in the literature can I find a taillight or brake light fuse designation, so I can't even check if the fuse is blown, although my taillights do come on when my lights are on. I'm thinking it's NOT my brake light switch at the brake pedal because my center brake light comes on when the pedal is pressed. Although there's a good few elec lines coming from the brake light switch, so who knows. Perplexed.

 

Check the ground wire on the bulb socket itself, they work loose over the years.