Fuse-eating alternator...

[XRzer04]

First off thanks, spiffyguido for answering my first post with alternator questions. So here's where I'm at now:

I just replaced the alternator in my 1989 Honda Prelude and now every time I reconnect my negative battery cable, I blow my main (70A) fuse. It's happened two times in a row.

Some background: My alternator burned out and stopped working about two weeks ago, but even before that, A mysterious drain appeared in my electrical system, causing my battery to go dead if I DIDN'T drive the car.
For example, If I drove it every day, it was fine, but if I skipped a day, the battery would be too drained out to turn the vehicle over. If I skipped two days the battery would barely light up the instrument panel.
So about two weeks ago, after the alternator left me stranded on the highway, I resorted to desperate measures.

I still needed the car to get to work, and I discovered that I could run it off the battery alone if I was careful, so I disconnected the alternator wires and started carrying around a second battery and a bench charger.
I would charge both batteries up, use one to get to work, then switch to the other for the ride home.

Somewhere along the line the unplugged 4-terminal plug that connects to the alternator touched the hot exhaust manifold and became a melted ruined mess.
When I installed the new alternator I worked around this by just cutting the ruined plug off and terminating each individual wire with a female spade connector the right size to slide onto the contacts inside the socket on the alternator.
I was Very Careful to make sure each wire was connected to the proper terminal in that socket, and double checked before attempting to start.

Besides the 4-terminal plug, there is also a single wire connection to the alternator, using a ring terminal held on with a nut. I believe it's the ground. I've isolated the problem to here.
The first time I blew my main fuse, this single wire was the only connection between the new alternator and the vehicle's systems.
This was actually left connected by mistake, but when I tried to reconnect the negative battery cable there was a big fat blue spark and suddenly nothing worked..

After locating and replacing the blown fuse, I totally disconnected the new alternator and the vehicle started up on the battery alone as it had been doing.
I turned the engine off, disconnected the negative battery cable again, connected the ground cable and the four terminal connections to the alternator,
and when I reconnected the negative battery cable, my main fuse blew again.

That's where I am right now
There is obviously a fault in the electrical system somewhere, and I don't know how to even begin to troubleshoot for something like this.
I don't have any choice but to deal with this myself.
I need Help.

[spiffyguido]

One clarification before we start troubleshooting about this:

After locating and replacing the blown fuse, I totally disconnected the new alternator and the vehicle started up on the battery alone as it had been doing.
I turned the engine off, disconnected the negative battery cable again, connected the ground cable and the four terminal connections to the alternator,
and when I reconnected the negative battery cable, my main fuse blew again.

When you reconnected everything, did the fuse blow right when you connected the battery? Or did it blow when you attempted to start the car?

[XRzer04]

...To answer the last question, it blew Immediately upon touching the negative battery cable to the battery terminal.

BUT... In the past week and a half a whole lot has happened with this project.

Iended up just taking the vehicle to a shop and having them diagnose it. The problem is they ripped me off.
I was told I needed a new engine wiring harness. Fair enough. They charged me $210.00 for something I could've
bought online from any one of numerous sources. I was told their part would come with a warranty, in addition to a labor warranty.
Again, fair enough.
Problem is, when I got the vehicle delivered back to my house, I looked under the hood, and the same old spade-connector field-expedient
replacement for the green alternator plug block That I put in MYSELF!! Now, I wasn't home when the car returned, or I would have said
something right then and there.
The person who recommended this shop to me decided to save face by calling them up for me and asking what's going on.
The answer she got was that the shop had installed (and charged me for) A "Partial" engine wiring harness, which only included the "Back end"
of the harness, meaning they only had to replace the part that Can't Be Seen from a casual underhood inspection, because the parts replaced were all
"behind the engine".

They picked my car up Sunday evening and had it ready by 11am the next day. I don't think there was time to remove the engine to get behind it,
so anything they could have possibly installed in the time they had should be visible, right?
Also-
I haven't ever changed out a wiring harness before but I've been researching this one and every one I've found for sale has been a complete unit- Never a "partial",
and every single one of them has included the alternator plug connection.
I think these guys lied to me and charged me for a part they never replaced. Thing is, Because I've never actually held an engine wiring harness for an 89 Prelude
in my hands, I still need that last bit of Absolute Certainty before I go confront these jokers myself.

So: My question to anyone out there who has done the procedure is: Am I Right?
Is there ANY such thing at all as a "partial engne wiring harness"?
Or Am I correct in my suspicions that these guys took me for a Ride?

[spiffyguido]

I've never heard of a partial wiring harness.

The engine wiring harness for the engine does run along the back of the engine. It is all one piece, including the part that comes over the right side of the engine to the alternator. I've attached a picture of it.

There are PLENTY of places where the wire harness is perfectly visible. It is even easy to see the parts of the wire harness that are behind the engine if you just lean over and look. You'd know if you had a new one, so unless they cut up your harness and spliced in a new section, you'd know if you got a new "engine wire harness".

There are other wiring harnesses in the car. In the engine compartment there is a wiring harness for the AC system, one for the left side of the engine bay, one for the right side of the engine bay, and a few for ground wires. All of these are significantly less complex than the main one, and all are well detailed in the service manual (available in the manuals section above) starting on page 16-8.

Your problem is certainly electrical, likely a short somewhere in the system. I think you're right to be cautious about the work that was supposedly done to your car. A wire harness is visible, and you'd know if you got a new one. Have a good poke around and see what you can find.