66 Corvette amp gauge

[Ken Harants]

I have my dash taken out of my car. The only gauge that didn't work is the amp gauge. Is there an easy way to test the gauge and the wiring to the gauge to find out why it wasn't working.

[William C.]

Re: 66 Corvette amp gauge

use a 1.5 volt battery and small jumper wires to connect across the terminals of the meter, just touch the wires to the terminals for an instant and you should see an immediate full scale deflection. DONT LEAVE THE BATTERY CONNECTED TO THE TERMINALS FOR MORE THAN AN INSTANT. If you see the movement, it likley is good. Most of the amp gauge problems are related to the connections at the front of the dash in the engine compartment, or at the starter. The system functions by measuring voltage drop across a feed wire in the engine compartment. See your service manual wiring diagram for the schematic.

[Richard S.]

Re: 66 Corvette amp gauge

Bill,
Since it seems there are many C2 owners who have amp guage problems.... I wonder if you or someone else could post a detailed description of exactly where the connections are in the engine compartment and front of the dash and how to trace/test for problems. I have the service manual but it's not always clear which color wire does what. If you know the details I'm sure it would help many of us who would like to do the repair ourselves. Thanks for your help.

[William C.]

Re: 66 Corvette amp gauge

The engine compartment side consists of two sensing wires, an 18 gauge black that connects thru the engine harness to the "B" terminal at the starter. The second wire is an 18 ga red that connects thru the harness to the center of the horn relay. both of these are in the same connection thru the dash, although I can't tell you which one it is right now. but if you are working on the engine compartment side the connections under the steering column you are at the right place to be. Clean all of the terminals on both sides of the connection while you are there, and if necessary, GENTLY reshape the contact surfaces to provide a little more force between the mating surfaces. These two wires look at the voltage drop at both ends of the wire that charges the battery and implies a current from the voltage drop using ohm's law. To do this, the meter movement must be sensitive, and the connections must be clean. Also check the connection at the starter, because if not connected at that end, the car will run fine, but no action will be seen on the ammeter (which is really a voltmeter).

[John H.]

Re: 66 Corvette amp gauge

On a '66, the ammeter sense wires are black to the battery cable stud on the starter solenoid, and black/white to the screw terminal on the horn relay. Both wires are in the inboard multiple connector on the engine side of the fuse block. Corroded or high-resistance connections between the male and female terminals in that connector for one or both of those wires is the usual cause of an ammeter that stays centered while the charging system is working fine.

[William C.]

Re: 66 Corvette amp gauge

I used the '63 wiring diagram for the example, wire colors and stripes with/without changed several times from '63-67

[Richard S.]

Re: 66 Corvette amp gauge

Bill and John,
Thank you both for the insightful information. You guys.... and the rest of the Board posters.... make the Classic Corvette world a better place for all of us.

[Randy S.]

Re: 66 Corvette amp gauge

I've been chasing this problem for 6 mos. My ammeter gauge moves about 1/16" pos and neg. the cluster rebuilder assured me the ammeter is correct. I confirmed movement with the AA battery test. I've cleaned the firewall connectors with dremel tool and used dielectric grease. I've got 12 v to ground at ammeter on both 18 ga black ( B term) and 18 ga black/white(horn relay)wire so I have connectivity thru the firewall connector.

Any other ideas?

Randy

[John H.]

Re: 66 Corvette amp gauge

Make sure the black wire connection at the starter stud is clean and shiny (and tight), and the same for the black/white wire connection at the horn relay screw terminal. The gauge is reading a very small voltage difference between those points, and resistance in the connections will affect its function.