Fuses 12 volt Lesson learned

[DougS]

Yesterday, I found the lights out over my sofa. Fuse was good. I took the two switches out and there was no voltage. I then pulled the paneling back, moved the wires around, and saw sparks, a wire came off its connection. After jumping the wire, the lights would not works. My meter showed 12 volts. After a timeout, I started from scratch at the fuse. I took a reading on both sides of the fuse and it tested good. I then pulled the fuse for a second look, it was burned. I guess it blow enough not to carry a load, but it still tested good, never had that happen before. Well I guess that's two hours I'll never get back.

 

[jimtoo]

HI Doug,

When the fuse was in the panel, was the red LED light on next to it indicating a blown fuse? If it was and you measured voltage across the fuse the positive side was probably reading 13.5v +-...and the other side was reading 11.5v +-. It would read voltage because the LED is backfeeding voltage to the fuse, but would not let any current flow because the fuse is burned. At least this is what I found on my unit after techs blew fuse and wired fridge direct. I did not like idea of fridge wired direct, even thou I was told fridge was protected by fuse on circuit board... Not true for the 12v. True for 120v a/c.

Jim M

 

[pegmikef]

I always ohm out suspect fuses because breaks are often hard to see visually so I rely on continuity.