Identifying Electric Short?

DougE wrote:
This is on a 2015 GMC Canyon but is really a generic question. There is a plate with non-replaceable fuses on top of the battery (see photo below).

Why are these fuses not replaceable? :h These are fuses available at any GM parts counter - I'm using an 80 amp version of these exact same fuses, purchased at my GM dealer, for use with my inverter.

These are standard bolt in fuses. Should be available at most auto parts outlets. Hope you never blow one of these large amperage fuses. You could have more problems then just a fuse!

You guys need to look at the picture more closely. These fuses only have a bolt connection at one end. The necked-down portion of the fuse is actually part of the plate. Yep, I've never seen this before either but if GMC is doing it, it must be the wave of the future. Even if I'm wrong, my original question is still valid and I wouldn't want to be blowing more of these fuses before verifying the problem has been identified and fixed!

These should be the fuses.
Bussman AMI fuses

If the fuse blows use a test light....

Hook the clip on the lead attached to the handle.. to the NEGATIVE battery terminal.

Now touch the positive terminal. LIGHT = GOOD dark = either dead battery or bad test light or bad connection.

Assuming light.

Now touch each of the LOAD terminals on the battery.. one afte the other

Light good, Dark blown. Problem found (if that is it's the fuse).

ANd wha't more.. No additional blown fuses.

wa8yxm - I'm not trying to identify the blown fuse, I'm trying to verify the circuit is OK before sticking another fuse in.

I use a Auto reset circuit ATC breaker. If a 30 amp circuit I use a 25 amp, If a 20 I use a 15amp. Always 5 amps lower than the circuit rating. I have a jumper with a ATC fuse connector with alligator clips on each end. IF it is a standard Glass or ATC spade in a fuse block I use the appropriate Auto reset breaker. SAVES time and money from continually popping a fuse trying to determine the short location. Doug

OPs photos show the main fuses, 300, 250, and 100 amp. I would not be replacing any of these with an auto resetting circuit breaker.

Grumble Snabble Snarf...

These are not precision fuses rated for load. They are Armageddon grade replacements for fusible links, got it?

If the 300-amp fuse blows it's pretty self-explanatory that you have China Syndrome and that isn't subtle.

The smaller rated fuses can be worked around in order to test a circuit. Their actual operating amperage IS NOWHERE NEAR the fail value. Not even close.

Disconnect the smaller fuse circuit.

With a home-made 50-amp breaker, 10 gauge lead wires and crocodile grade jaw clamps, hook this IN SERIES with the breaker circuit you wish to test. Do not try this with a low battery. Nor try with a great load placed upon that circuit.

Testing needs to be done, one additive load at a time. If one particular circuit is on the ra... oops I mean malfunctioning, you'll find it in a hurry.

If the big momma fails you won't need a magnifying glass a Sherlock Holmes hat to find the problem. Connect a 50 watt 12-volt drop cord bulb and standard socket in series with the big breaker and when it goes out or gets really dim you've hit the jackpot.

The in-series 50 watt 12-volt drop light test will also work great for the other fuses too.

Simple CHEAP home-made testing at it's finest.

Okey dokey - 50 am circuit breaker with a wire and clamp on each side. Bridge across the dead fuse location. Since I've got a spare on hand I might add a manual disconnect switch too so I don't get sparking when I put the clamps on the terminals. Thanks!