No crank, no lights, help!

Short to ground testing with a test light is simple, understanding/preping the circuit so the test is valid is where the trickyness comes in.
You simply connect the ground lead of the test light to battery positive, touch the tip to the circuit you want to check, and see if it lights. If the circuit is disconnected at both ends and the light lights then that wire is shorted to ground somewhere.

 

I haven’t don’t these steps yet. I’m just about to do them. But I put the multimeter to ohms, touched the alternator and the output terminal on the alternator and I got no resistance at all. Doesn’t this mean that the alternator is grounded out? And that’s why it’s sparking?

 

Yeah, but OP doesn’t have test light.
I’m trying my best to come up with a solution by working with what he has.
Which is only a voltage meter…….
And explaining it the best I can, which is actually harder than it seems.

Honestly, I’d be at the alternator myself with a test light.

 

Was the wire hooked up to the output terminal?
If so, it could still be the wire. (It’s probably not though)

 

No, the wire was not hooked up.

 

@Dm93 can correct me if I’m wrong.
But I think you will have continuity by checking case to post depending on the direction the meter is hooked up.
It’s basically a big diode, you need to check continuity (ohm) both ways.
A diode allows current one way, but not the other.

 

You are correct in that a diode will only pass current in one direction but I'm not sure an ohm test would work on a diode, I don't know I've never tried it. Most meters have a diode test function.
Testing for shorts to ground with a meter is something I rarely do, I do all short to ground testing with a test light as it's an easy visual reference when wiggling wires or unplugging things to see when the short clears.
We pretty much know there's a short since the fuse is blowing, the problem is finding it. Since it appears to have happened after the alternator was changed it has to be something that happened to the wire in that area or a faulty alternator.

OP you have pics of the alternator install?

 

Using ohms to test a diode will work.

When my last test light got stolen, and the 2 before that broke I gave up on them and just use my meter. Yeah there are times I wish I didn’t need to twerk my head to see what the meter is reading.

 

Really the only times I use my meter is to check battery voltage, check 5v ref at a sensor, or to check current, test light or scope for pretty much all other checks.

This is my short finding and high current power checking test light, if I have a fuse blowing I put it in place of the fuse and isolate things and move harnesses until it dims or goes out to find the short.

 

Looks like the other guys have you covered, but what I mean is that fuses do not just blow normally. They break because of a wiring problem to protect the circuit which in a car is usually a short to ground somewhere.