One of the best ways to find a short is to put a light bulb in the fuse circuit. Yes, remove the fuse and solder pigtails on a light bulb and watch the brilliancy. If you have a dead short it will light bright when the short is removed it will be extinguished or dim. Play with the wires etc. This is much easier than constantly blowing fuses.

Mownie - Your posts are fantastic. Thanks. I do have the JD manual but as you say, the schematics are not great. I do have the seat switch unmounted so no frame short there. Pink wire doesn't seem to be the problem - fuse blows with X3 and X4 connectors connected (ignition on, seat switch depressed, and all other components and switches disconnected) but does not blow when X4 disconnected and pink wire 800 isolated and connected alone to its post on IM. It's odd that with X3 connected, no individual wire in X4 will cause the fuse to blow, but when all the wires in X4 are plugged in, the fuse will blow when the ignition is on and the seat switch is depressed (and all other components and switches disconnected). Makes me think the IM is bad but I'm still not sure. Also, I did find that if X3 connected and X4 disconnected, connecting yellow-black wire 410 in X4 to its post on IM will cause fuse to blow (again with ignition on, seat switch depressed, and all other components and switches disconnected). 410 goes to ground. Again this makes me think the IM is bad. Also, I'm not sure how IMs go bad. I was just mowing the lawn, hit a bit of a bump (nothing unusual) and the tractor just shut down. I guess it's just as likely that a circuit board just dies as some other components. I figure a wire shorted due to a physical abrasion or corrosion would more likely be somewhat intermittent while my problem is not at all intermittent. Any additional thoughts before I replace the IM?

Your tractor has 2 Operator Presence Relays (OPR) They are Bosch relays, which look like this. Pins will be numbered 30, 85, 86, 87 & 87A. IF either isn't "activating", it will blow the fuse. Temporarily, unplug both of them. OPR1 contains the kill circuit for the engine. However, the fuel shutoff solenoid will also kill the engine. Just not as fast. OPR 2 is for the stator brake. Without it, the engine will not stop as fast. Examine the plugs closely. A burned contact may prevent proper operation, resulting in a short. You can get these relays at an auto parts store for much cheaper than a "tractor store". NEITHER are needed to operate. They are for safety reasons!! Those would be the likely suspects. The only other places that would possibly short (other than a melted wire) would be seat, clutch and attachment clutch switched. They would pretty much have to be "broken".

OK, let's concentrate on the ammeter. Does this ammeter mount in a metal panel? or is the dash plastic? If the dash is metal, it is possible that the ammeter is shorting to ground internally, but don't rush out and buy another ammeter yet, there are some tests to do first. Do you own a multimeter (that will test volts, ohms, and continuity)? If not, you need to buy one before doing any testing. This may take several posts to get to the root of the problem. If the ammeter mounts in a metal panel, set the multimeter to Ohms or to "continutity" if you have that feature on your meter. This test applies ONLY if the ammeter mounts in metal. If dash is plastic, skip this test. Unplug the wires from the ammeter. Place one of the test meter leads on one wire post of the ammeter and the other test meter lead on a clean, bare metal part of the tractor. You should read "infinity" if using an Ohmeter, or "no continuity" if using continuity setting. Test both of the posts on the ammeter and they should both show infinity or no continuity. If either post of the ammeter shows continuity to ground, the ammeter is shorted internally and needs replacing. Get back with some test results. Alternatively, you can test for a shorted ammeter by connecting together the 2 wires that attach to the ammeter. If you connect the 2 ammeter wires together and the fuse does not blow, you have proved the ammeter to be shorted.