12V Conversion Problem

First, sorry for the long story but I'm fustrated since I've been working on this thing off and on for three days now. I bought a 12V conversion package from a NC company and their diagram shows a wire from the Battery Terminal on the Solenoid going to the NEGATIVE TERMINAL on the Ammeter (Voltmeter). Now I admit that the medication the doctors have me on makes me a little slower than I was 40 years ago when I completely rewired a car so I questioned them about the wiring and was told to follow the diagram (basically asked if I could read a diagram). I got everything hooked up and put the positive on and set the negative cable on and smoke flew because I had a little trouble getting the cable back off (maybe a second but seemed like a minute). The result is in the picture. No one is answering the phones where I bought it I guess because of the holidays but I since some of you have converted I bet you can tell me how to fix it. I know I'll have to make another wiring harness because this one is mostly toast but I can use parts of this one.
This is how it was wired with the resister screwed in place with center post up: wire from alternator to center post on resister, wire from coil to right post of resister, ignition switch yellow to center post of resister, ignition switch black to left post of resister, solenoid strap in place, solenoid, small post wire to starter switch, solenoid Battery to 12V Battery, solenoid battery to negative post of Ammeter, jumper from positive of Ammeter to center post of resister, and finally negative on battery grounded to frame of tractor.
The only wire that burned was the wire was the wire running from the solenoid Battery to the negative post on the Ammeter. The Ammeter was attached to a 12V battery prior to this to see if it still worked and didn't show any problems.
HELP! grhouse

Gene...call me. don b1

This is the Ammeter and I think this is the problem. I received a phone call from my supplier who suggested that I must have connected the wire from the solenoid Battery post to the mounting post on the Ammeter. I was fairly certain that I didn't considering that I took it off first to ascertain exactly which posts to use. If you look at the picture you'll see the mounting posts at about the 10:00 and 2:00 positions and a red wire attached to the positive side at 4:00. The negative side is in the 6:00 position and there is a "S" next to the post in the 8:00 position. Hooking this meter to a battery with the "+" and "S" gives you nothing but if you use the "-" you get a reading so I used the "-".
My bad! As you notice, which I didn't, there is no insulation protecting the negative post from contact with the body of the meter and, since the meter is mounted in the frame of the tractor it created a hard ground with the solenoid Battery wire attached to it.
I'm going to have to buy a new meter I think!!!!
grhouse

I forgot to add that my supplier called me back even though everyone else was off for the holiday! Now that is good service. grhouse