Volt meter/ amp guage

[brokenspoke]

Has anyone replaced the amp guage with a volt meter in a 1965 truck....I understand the amp guage isnt safe compared to volt meter.....When did chev start volt meters? I wonder if another year guge will fit in shock location?

[TR65]

The ammeters in our trucks are perfectly safe. They measure the current draw indirectly. One wire attaches to the battery positive at the starter, the other wire goes to the power distribution terminal at the horn relay. None of the truck operating current runs through the ammeter. If the battery voltage is higher than the voltage at the horn relay, then current is flowing out of the battery, discharge state. If the voltage is higher at the horn relay, the alternator is keeping up and sending current to the battery, charge state. So a small current flows through the ammeter with the direction depending on charge or discharge of he battery.

Nothing wrong with a voltage gage either though, but I like the ammeter.

TR

[ray_mcavoy]

Hi brokenspoke,

I believe GM changed to voltmeters in 1976.

Ammeters aren't necessarily unsafe compared to voltmeters. It all depends on the wiring.

Aftermarket ammeters often run the full system current through the meter movement itself with heavy gauge connecting wires running inside the cab. These can be dangerous if they're not protected by a large fuses or fusible links.

The factory ammeters in these trucks make use of the existing battery charge wire (that runs across the radiator support) as a shunt. So normally there's very little current flowing through the meter movement and connecting wires. However, if there's an open circuit in the shunt wire (due to a bad connection or whatever), enough current can flow through the meter movement to melt the connecting wires. I've seen the results of this on several melted wiring harnesses.

GM did use some small 3 or 4 amp inline fuses on some trucks to prevent that from happening. From what I've seen, the inline fuses are more common on the 67-up trucks. But can easily be added to the older ones. I added them to dad's 66 when we swapped in a factory gauge cluster.

[brokenspoke]

Thanks ...I think I'll leave alone....I was just upgrading alternator to higher amp....and thought it would cause a problem