This is an excellent reason not to bypass it.
Here's the basic concept.
Cars have two power sources: Battery & Alternator.
Power flows from whichever one can supply at the higher voltage.
1. Battery can supply power at approximately 12.5 Volts.
2. Alternator can supply power at approximately 14 Volts.
So when the engine is running, the system has14 Volts in it.
The main wire from the battery goes through the ammeter.
The ammeter shows if the battery is discharging or charging. In other words it shows how many electrons are moving into or out of the battery.
The output wire of the alternator joins the battery output/recharge wire on the other side of the ammeter.
On the standard wiring used from 1964-73, the main circuits are all joined at a welded splice (shown as a solid circle in the diagram below).
When the engine is running and the battery is charged, electron flow looks like this.
View attachment 1716021338
The ammeter shows zero because the battery is not supplying power, nor is it getting recharged.
Ifthe ammeter stays near either extreme, there is a problem and the engine should be shut off.
The ammeter is calibrated aprroximately 40 amps discharge to 40 amps discharge.
A fusible link in the line helps protect against a short to ground, but will not melt completely at 40 amps. However damage to connectorswill likely occur faily quickly.