1963 corvette ammeter repairs itself!
Thread Starter
Racer
Joined: Nov 2006
Posts: 461
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1963 corvette ammeter repairs itself!
Thought I would pass this interesting happening One day my ammeter started buzzing, and red needle went down to left side flat. Ammeter was not functioning and it looked like a replacement and headaches were needed. While fiddling with rear ammeter connection (battery off) the ammeter needle shot up to mid guage!. Turned on battery and checked ammeter with motor running and registers normal, charge and minus charge when engine stopped with light on! Operating normal now! WOW! any thought on what happened? loose connection? short? good luck to all, Abe G
2nd Gear
Joined: Aug 2006
Posts: 2
Likes: 1
Lurking problem...
I just happened to see your post today since I'm making a custom engine harness for my '64. An important wire in the harness is the 10 gauge (red) that runs from the starter solenoid Battery terminal to the +12v bus on the horn relay. It is across this wire that the ammeter senses voltage drop and that translates into the amount and direction of current flowing to/from the battery for everything electrical in the car except the starter.
The ammeter is actually a sensitive voltmeter (millivoltmeter) and the 10
gauge wire acts as an external current shunt for this meter. The internal resistance of the meter is about 1.4 Ohms from a measurement I made. The resistance of the 10 gauge wire is a lot less and probably on the order of 50 to 100 times less, so most of the current flows in the wire and only a smaller fraction flows through the meter. However, should the 10 gauge wire connections get loose, a much larger than normal current will flow through the meter in an attempt to supply power demanded by whatever is 'on' in the car. The conclusion that you have a bad connection is correct and it's in the 10 gauge wire probably at one of the two ends where the terminals are crimped. There should be a smaller (in gauge) black wire with the 10 gauge red wire crimped together in a common lug on the starter solenoid Battery terminal. At the horn relay end, a smaller gauge black/white wire is crimped with the 10 gauge red wire in another lug attached to the +12v bus bar. These smaller gauge wires go to the ammeter through the bulkhead connector on the firewall.
I think you'll get the idea after looking at the ends of the 10 gauge red wire. BTW, NO electrical problem actually cures itself. They actually lurk in hiding waiting for the opportunity to re-occur at the most inconvenient time for you.
The ammeter is actually a sensitive voltmeter (millivoltmeter) and the 10
gauge wire acts as an external current shunt for this meter. The internal resistance of the meter is about 1.4 Ohms from a measurement I made. The resistance of the 10 gauge wire is a lot less and probably on the order of 50 to 100 times less, so most of the current flows in the wire and only a smaller fraction flows through the meter. However, should the 10 gauge wire connections get loose, a much larger than normal current will flow through the meter in an attempt to supply power demanded by whatever is 'on' in the car. The conclusion that you have a bad connection is correct and it's in the 10 gauge wire probably at one of the two ends where the terminals are crimped. There should be a smaller (in gauge) black wire with the 10 gauge red wire crimped together in a common lug on the starter solenoid Battery terminal. At the horn relay end, a smaller gauge black/white wire is crimped with the 10 gauge red wire in another lug attached to the +12v bus bar. These smaller gauge wires go to the ammeter through the bulkhead connector on the firewall.
I think you'll get the idea after looking at the ends of the 10 gauge red wire. BTW, NO electrical problem actually cures itself. They actually lurk in hiding waiting for the opportunity to re-occur at the most inconvenient time for you.
