Hello. I have a 1992 i6 f150 auto. I noticed that 1. my battery was always drained. 2. my turn signals interrmittantly work. 3. I now realized that when I press on the brake pedal the fuse blows. in addition, when checking the tail light sockets the bulbs were lit without pressing on the brake(I checked the switch, its fine).

I disconnected the wiring underneath the back of the truck to see if perhaps a socket was causing it to blow and took the bulbs out and it still blows the fuse when I hit the break.

Any ideas?

 

The brake filaments were lit when the fuse was blown??? Or was it the park filaments? Were they full-bright, or dimmer than normal?

Look for aftermarket wiring spliced into the brake circuit, like a trailer connector, or an alarm.

 

The two times I've seen this came from a hacked up trailer connector install, and a miswired brake controller.

Adrianspeeder

 

After staring at the wiring schematic for what seemed to be days and testing the circuit to ground, I found the problem.
The problem was a grounded positive wire that came from the brake pedal switch to the multi-function switch. So instead of pulling the dash completely out, I ran a new wire and soldiered it in there.

Thanks,
Matt

 

I'd be REALLY curious about why/where the original wire shorted. If something was assembled wrong & pinched it, others could soon follow.