I have a 93 4Runner an a few days ago the fuse popped. I changed out all the old lights to new, spent many hrs tracking down the wires to see if there was a bare wire exposed. Here's the catcher.. It all works while I'm parked but 5 mins on the road it pops again! I don't get it any ideas out there before I go nuts!?

 

intermittent shorts to ground can be a royal pain, what I have done in the past was to put a slightly larger fuse in the original and put the rated fuse farther along the circuit with slightly smaller ones on each branch of the circuit. you'll have to go to the wiring diagram to pick where each should go. at least put a smaller fuse at each light. if the main blows your short is between that and the next fuse. if one of the smaller branch fuses blows your short is on that branch and the remaining branches will still work. good luck

 

Now you are talking tail lights here .

Try swapping a good tail light relay in see if that cures your problem .

Might be a problem in either the coil or the contacts in the relay once it gets hot it draws to much and opens the circuit protection.

 

My break lights work just fine. Its the 2 front corner lights, the dashboard, license plate lights or also know as the parking lights.

 

if it gets to where it's repeatable in the driveway you could remove all of the loads and disconnect sections of the harness checking for a short to ground, but with an intermittent you will be better off with the divide and conquer method with progressively smaller fuses strategically placed on each branch of the circuit. running lights/dash lights/ license plate lights will lead you through a lot of harness. best to figure out which leg/branch to be looking at.