I wish I could get Ron to help me make my factory 1987 ammeter working again after my 92 5.0 swap...
I don't think Rangers ever used a calibrated AMP Meter, so they didn't need a calibrated Shunt
Rangers just had D for discharge, and a C for charge, needle moved from center spot towards D with key on engine off, then moved towards C with engine on, IF alternator was working
Like this one:
https://www.ranger-forums.com/attachments/snapshots-69/186209d1501440305-1987-led-gauges-1.jpg
Non-calibrated is important because its much easier to install
A calibrated AMP meter would have numbers, i.e. -80amps to +80amps, these require a calibrated Shunt
A "shunt" is any wire or connection used between the two wires of an AMP meter, so its not a specialized device, its just what you call the wire between the two amp meter wires, the wire that most of the electricity passes thru is "the shunt"
In this application the Shunt is the B+ wire from alternator to the Fuse or fusible link
All the amps from alternator go thru this wire to the battery, the amp meter has two wires, one connected to B+ and one connected to Alternator side of the Fuse/Fusible link
The direction of the flow of electricity thru this "Shunt" wire is the D or C, so if AMP Meter seems to read in Reverse, then just reverse the 2 wires, no harm done
Diagram here of Ranger AMP meter wiring:
https://www.therangerstation.com/tech_library/EDiagrams/files/diagram_charging_1983to1985_1.JPG
Black/orange(BK/O) wire is the Shunt wire
Alternator(B+ terminal)\------------(black/orange wire)---------------/Fusible link------Starter relay post(battery positive)
.................................................\--------------AMP Meter-------------------/
You need AMP meter wires protect by the fusible link, you could add a 5amp fuse on either Meters wire for more protection
You CAN cut the Black/orange wire in one place(near fuse) then use butt connector to splice in the amp meter wire, or in two places, that's what Ford did on their factory wiring
This is technically a Charge-Discharge meter since it doesn't display actual AMPs, lol, like starter relay or starter solenoid
When you do an AMP meter then you need a Shunt wire of a calculated size/resistance to match the AMP Meter
The smaller size Shunt FORCES a known percentage of AMPS thru the AMP Meter, so it can show an actual number, like +30amps, or -10amps
You can buy AMP meters with built in Shunts, however..............................you would need to run LARGER wires than on B+ now, from alternator into the cab to the AMP Meter and then back out to the battery, lol
Years ago these were used in cars and trucks but alternators were 30-40amps then, not the 70-130amp models now-a-days