An In-circuit Car Fuse Tester

**rgsparber** · Jul 18, 2019, 10:12 PM

Originally Posted by VinnieL

A test light or digital voltmeter works very well. The two terminals of the fuse are available on the top of hte fuse. You don't even have to remove the fuse. Just touch the two probes to the two terminals on top of the fuse. If there is NO voltage there (or test light does not light) the fuse is good. If it lights or you detect voltage the fuse is blown. Technically you are reading a voltage drop. It there is a 13-14 volt drop the fuse is shot and needs replacing.

And if there is no voltage on the input and the fuse is blown?

Rick

**mbshop** · Jul 25, 2019, 04:55 PM

Sorry, but I'm confused. As a tech and shop owner for over 35 years that's hard. Fuses are easy. Use a test light. Wire to ground, probe to fuse. If your probe lights up on both sides, fuse is good. If probe lights up on one side, fuse is bad. That's the easy part. If probe does not light up on both sides, make sure that circuit is powered up. If a fuse shows ok but circuit is still not powered up then you have another issue. Start checking the fuse contact first as they do corrode. After that the fun begins.