I am trying to fix my headlights and i checked the fuse and it is blown so im assuming that its a short. I put the red lead on my multimeter in the fuse slot and the black to a ground and it is showing 12.31V. This is with the power off, and i thought that with a short there should be no volts and then you move the wiring harness for the component and if the test light or meter shows voltage the short is in that area. Am i doing something wrong? please Help me so i can find this short.

 

depends on which side of fuse you were testing, one terminal goes to the battery the other side goes to the intended circuit.

the battery side will be "hot" as it is not controlled through the ignition switch. larger loads will be connected to the battery controlled through relays and the relays are controlled by the ignition power.

you can use the continuity feature ( it will make noise) by connecting red to circuit and black to chassis, it will read continuity through lamps and controls so as you "clear " or disconnect these you will loose the connection and then no reading. if you have all lamps unplugged and head light switch turned off you may need to check each wire.

 

9 times out of 10 a blown fuse is a short to ground.

Fuses & other circuit protection devices normally never wear. They fail because something is wrong. Don't just replace a fuse or link, rest a breaker with out diag!

A good fuse will have zero resistance "ohm"

 

If you are ohming a fuse, you have to remove it. NEVER use an ohmmeter on a live circuit unless you know exactly what you are doing.