I just bought a 1994 f150 and the brake lights, turn signals, hazards fuse keeps blowing. I replaced the fuse and noticed the interior light came on when I hit the brake, as well as the brake lights. all I had was a 30A fuse and it lasted about 30 seconds before it blew.

I also noticed the running lights fuse was missing when I bought the truck, replaced it and havent found any issues other than no clearance lights or passenger mark light work. All other lights are good and that fuse hasnt blown.

My question is am I going searching for a wire grounding out? Or is this a symptom of headlight switch going bad? And could my interior light be related? Previous owner seemed to hack a lot of the wiring up..

 

Do you have a 3rd brake light ? If so pull it and your interior light and look for a possible short there. Interior light shouldn't come on with the brake light.

 

could be a short

 

Both the interior and 3rd brake light had a short! I had checked the interior light first but didnt even think about the 3rd brake light. Thanks!

 

I lost my brake lights again.. got pulled over for no brake lights. Fuse is good though.. I put in a new brake light switch and still have no brake lights. Flashers still work. I don't get it. I had them and earlier. Woke up to go to work and no longer have them.

 

You checked the bulbs, right ?
If you straightened out the wiring to the 3rd brake light, there could be something else in the harness to the back. Be especially suspicious of any trailer wiring hookups.
Do the front marker lights come on ?
Could be a problem with your headlight switch, but eliminate all the simple stuff before you think about going there.

 

I assumed the short at the interior light stopped at the light itself.. but the wire is burnt all the way to behind the dash and I assume fuse block. It burnt through the insulation but it doesn't look like it messed with any of the other wires. How do I get to it? I couldn't get the fuse block out to where I could see the back.

Also the remains of the #8 fuse were burnt up. I hadn't noticed this before but it is probably the cause. I'm okay with just getting rid of any non necessary lights. I just want brake, turn, running, and headlights.

 

Unbolt the fuse block. 7 or 8 mm