Yes, me either.
1988 could have an AMP gauge or a volt gauge
AMP meters were mostly used with Generation 1 alternators with external voltage regulators
Gen 2 and up used internal voltage regulators and a Volt gauge in the dash.
The volt gauge just hooks to any Key on 12volt wire in the cab and a ground, so not much to it.
An AMP meter has two parts, the amp gauge in the dash and then an AMP Shunt, in the engine bay.
You don't want to run a 90amp wire in and out of the cab, lol, just asking for trouble doing that.
So an AMP Shunt is used to pass 99% of the amps from alternators B+ terminal to Battery Positive(starter relay on fender)
The Amp gauge's two wires are hooked on either side of the Shunt, and see 1% of the amps going to battery, the gauge is calibrated for the Shunt used, or some AMP gauges are just + and -
Diagram of AMP Shunt wiring here:
http://www.therangerstation.com/tech_library/EDiagrams/files/diagram_charging_1983to1985_1.JPG
AMP or Volt gauge is not "part" of the charging system, meaning if either is bad or disconnected it would not effect charging, they are just monitors of the system.
AMP Shunt is part of the charging system, a big part, a 99% part, lol.