Alternator overcharging

I?ve got an older Gehl skid loader, 4 cylinder ford engine, runs out great. It has sat since the fall, needed a jump today and it took awhile but it started. The ammeter is 0-30 amps and the needle was way past 30 today and I noticed a little smoke coming out from the dash. The negative terminal of the ammeter is getting HOT. I took an old dead battery that I had laying around and put it next to the one currently in the skid steer. I started the engine and then swapped the battery cables from the newer battery to the dead battery. The ammeter showed it was charging around 15 amps and never got hot like before. No smoke, no issues and it kept on running for about an hour. The old battery is taking a slight charge as it will turn on the fuel pump and the solenoid will click a couple times. The alternator and the voltage regulator are new as of August 2019. Has the battery got a bad cell? Any thoughts or experiences with this are appreciated.

If you switched batteries and it fixed then the battery is probably bad

Chances are the battery is bad, or at the least severely discharged, both of them.

A couple of problems, the alternator is primarily designed to maintain charge in the battery as power is consumed by the vehicle.

It is NOT intended to charge a dead or defective battery! Doing so is an open opportunity to damage the alternator or the electrical system (as in the smoking amp meter connection).

Hopefully the alternator is not damaged. The amp meter will need to be looked at, could have damaged the meter or the connection. It may be working now, but soon the damaged connection will begin to loosen, corrode, and cause problems later on, about the time you forget about it being overheated, and you'll spend hours looking for the electrical Gremlin! LOL

The solution is to inspect and repair the amp meter connection, replace the amp meter if any doubt. Charge the batteries, have them load tested. If they pass, slow charge them to full charge, try again. Start the engine, bring the RPM up, check the voltage across the battery. It should run around 15 volts max. If above that, it is overcharging, if below around 14 it is under/not charging.

And please don't be disconnecting the battery while it is running! Dangerous to your health (as in an explosion!) and can damage electrical components, especially any electronics, including the alternator, regulator, ignition system, computers, or solid state accessories.

Connecting the batteries in parallel + to+ and - to - then disconnecting one of them is OK do not disconnect the battery and then attach a dit=fferent one while running. An alternator can and will make enough voltage to ill you and or ruin all attached light bulbs and electronics. seriously.
Also pull the terminals off the ammeter and polish them shiny. Jim

Most likely you have a bad battery AND a corroded ammeter terminal.

When one sees evidence of heat one thing that comes to mind is a bad/loose/resistive connection or excess current. It wouldn't hurt to check each and every ammeter and battery and ground big cables and the smaller wiring connections such as the ammeter and charging system. A battery problem such as a short or bad cell or others might cause heavy current draw. The battery can be load tested at a local shop usually for free, if other batteries work fine but only the one causes problems, that may be it ?? Not hard to have it tested nor is a simple check of all connections..

John T

low battery fluid/acid/water level will cause over charging. And if this goes on too long it will ruin the battery. And maintenance free battery's can get low on fluid too.