Weird fuse issue

[Tooeez]

I wanted to pass this along in case anyone else runs into a similar issue--I've never run into anything like it.

So the background is about 2 months ago I replaced my 28's cable steering system with a hydraulic system, which means I spent a lot of time curled up under the flybridge retrofitting the helm pump into the space behind the dash, pushing all the wiring back and forth. When I got done the steering worked fine, but none of the electronics, except the radar, had any power. I have fuseblocks with the glass fuses under the flybridge, so I went back in and removed and cleaned all the terminal connections and fuses. After that everything worked, except the radar! No screen, no beeps, no scanner, nothing--acting like it had no power. Since it had worked fine the day before I thought it had to be a wiring issue. I removed the fuse and checked the continuity between the ends of the fuse--good. So I broke out the multimeter and started from the source--12.7 volts at the feed wire to the fuseblock, 12.7 volts at the line side of the fuse, 12.7 volts at the load side of the fuse, and 12.7 volts at the plug at the back of the radar. There are no fuses inside the radar, so why won't the damn thing work?

When you have eliminated the impossible, whatever is left, however improbable, must be the answer. The only variable in the circuit is the fuse, so after checking everything else three times I clipped a jumper wire to both sides of the fuse and the radar powered right up. I replaced the fuse and everything is back to normal. Apparently the original fuse, even though it had continuity and even though the correct voltage was passing through it, had some internal defect that did not allow enough current through to operate the unit.

[Tony Meola]

Depending on the type of fuse, fast blow vs slow, you may have had a broken link that was touching when turned a certain way then when installed, the position changed and the wire separated. Something like when an incandescent light bulb burns out but when you turn it to replace it, it goes on. The filament breaks but when it is jiggled it makes brief contact to complete the connection and light the bulb. Temporary at best. Usually stops working as soon as you turn the light off.