As some owners now replace their original electric generators with a modern alternator, here is an important warning that must be considered.
This is in regards to the in-dash original amp gauge used on most all vehicles. This gauge was made for a lower amperage flow provided by the early factory generator, usually a max of about 35 amps (sometimes 45 amp if factory air conditioning) on most 1950’s vehicles.
When a modern alternator is added, sometimes they have the ability to create a current as much as 75 amps. Sometimes this is not good! The original dash amp gauges were not made to carry this high charging level and they could be permanently ruined if one thing happens.
If your alternator equipped older vehicle has a totally drained battery (lights left on, small electrical short, etc.) there may be trouble.
The alternator charging the dead battery starts operating to its full capacity when the engine begins running. Remember during this charging period, if it’s a 60 to 75 amp alternator, it may ruin the original amp gauge with the “catch-up” to reach full battery charge. If the battery is almost at full charge, no damage will occur. The older amp gauge is not made to withstand this high current flow.
The older gauge can be identified by the two posts on the back side (positive and negative post). All current created from the alternator passes through the amp gauge. If this is a concern, running the current through an add on volt meter below the dash will be the option or use an alternator with not over 50 amp charging capacity. A 50 amp alternator will provide the service most require on older vehicles.