The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 1966 ammeter with new engine, alternator, and wiring harness

**VetteVet** · 05-24-2017, 12:37 PM

I wouldn't get caught up in the accuracy of these ammeters. They are basically just indicators of a charge or discharge of current from the alternator or the battery, whichever is the higher output, by measuring the voltage proportion between the two. In other words which one has the higher voltage. IF it's the alternator you see charge and if it's the battery you see discharge.

Here is a thread that gives more information.

http://67-72chevytrucks.com/vboard/s...d.php?t=393139.

This thread is on the 67- 72 trucks but it is virtually the same ans the 63-66 models.

In addition you stated the resistance on the SHUNT as a 10 gauge AWG wire.
In the factory configuration the SHUNT is a 12 AWG wire. Given the mission of the ammeter, I don't think that makes much difference. Also your understanding of the alternator ampere output is flawed. The alternator will only supply the amperage needed by the system regardless of it's total capacity.

I have my alternator (100 amp 12SI ) installed on the passenger side and I still ran the SHUNT, between the battery and the main junction with the alternator output, and the rest of the truck circuits. Your horn relay is the main junction, so you should run your alternator output there, as well as the battery charging wire, AKA the SHUNT.

The highest output you should see from the alternator will be 18 volts which will be unregulated if it malfunctions. Voltage range then will be 0 to 18 volts.

Simply measuring the resistance across the ammeter gauge should give it's internal resistance.

There should be plenty of resistance charts on awg copper wires on the internet to give you the values you need for a given length of 12 or 10 gauge wire. I would figure about 4 feet for length.
HTH

05-24-2017, 12:37 PM	#2
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,705	Re: 1966 ammeter with new engine, alternator, and wiring harness I wouldn't get caught up in the accuracy of these ammeters. They are basically just indicators of a charge or discharge of current from the alternator or the battery, whichever is the higher output, by measuring the voltage proportion between the two. In other words which one has the higher voltage. IF it's the alternator you see charge and if it's the battery you see discharge. Here is a thread that gives more information. http://67-72chevytrucks.com/vboard/s...d.php?t=393139. This thread is on the 67- 72 trucks but it is virtually the same ans the 63-66 models. In addition you stated the resistance on the SHUNT as a 10 gauge AWG wire. In the factory configuration the SHUNT is a 12 AWG wire. Given the mission of the ammeter, I don't think that makes much difference. Also your understanding of the alternator ampere output is flawed. The alternator will only supply the amperage needed by the system regardless of it's total capacity. I have my alternator (100 amp 12SI ) installed on the passenger side and I still ran the SHUNT, between the battery and the main junction with the alternator output, and the rest of the truck circuits. Your horn relay is the main junction, so you should run your alternator output there, as well as the battery charging wire, AKA the SHUNT. The highest output you should see from the alternator will be 18 volts which will be unregulated if it malfunctions. Voltage range then will be 0 to 18 volts. Simply measuring the resistance across the ammeter gauge should give it's internal resistance. There should be plenty of resistance charts on awg copper wires on the internet to give you the values you need for a given length of 12 or 10 gauge wire. I would figure about 4 feet for length. HTH __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.