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I have a 67. When I start the engine the ammeter needle moves to the left and it goes back to center when the engine is turned off. I have had the alternator and voltage regulator tested and they both check out. The ammeter and battery are brand new. The car has an MSD box and Pertronix in the stock distributor. At rest the battery reads 13 volts across the terminals. In idle the voltage starts to creep up at the terminals. Any input or help would be greatly appreciated. Thanks Mike
What happens when you turn the key on and don't start the car?
Any chance you reversed the black and the black/white wire on the back of the BATTERY gauge? (We can discuss why it's not really an ammeter later if you like). A good test would be turn on the key, see if needle changes, then turn on the headlights, if the needle swings to the right, you have those two wires reversed.
Last edited by 65GGvert; Feb 28, 2018 at 09:17 PM.
I am restoring the car . The wiring harness is new and most of the electrical is not connected except the fan , turn signals and dash lights. The car starts right up and runs well
There is a black wire running from the starter to the horn relay. The battery gauge works by reading a voltage drop across this wire, negative or positive depending on whether the battery is charging or discharging. You have to have that wire to get a gauge to work properly. I ask again, any chance you reversed the black and black/white wires at the gauge.
The black/white wire from the gauge connects to the red wire at the horn relay terminal and the black wire from the gauge connects to the battery lead wire at the starter. The other black wire from my first paragraph connects the two 12v sources together so the gauge can read the voltage dropped across the small resistance that wire provides. It seems to me that if you turn on the key and the needle doesn't move, but reads negative when the car is running, those two wires must be reversed, either at the gauge or on the other ends.
First, I want to thank you for taking time to help me. I greatly appreciate it. I suspected the horn relay but wasn't really sure. I have a blown up wiring diagram so I will double check my connections when I get home this evening. There is a molded two wire connector at the ammeter which can only go on one way so I believe the issue will be at the horn relay
A thought, you said "fan" is connected. I assume you have installed an electric fan. You may be reading the draw on the fan if the charging system isn't working correctly. Try disconnecting the fan and see if your needle goes to zero.
Edit: Another thought. Probably not, unless the fan doesn't run until car heats up. You said the needle doesn't move when you turn the key on without starting, so that would test the fan draw with no charging if it runs anytime the key is on.
There is a molded two wire connector at the ammeter which can only go on one way so I believe the issue will be at the horn relay
With a reproduction wiring harness that is not a sure thing. My Corvette reproduction harness had the leads reversed in the two-plug connection to the fuel gage and I had to reverse them. A new harness in another car I have had a plug with two wires reversed in position. If the leads to the plug are reversed it's pretty simple to use a small screwdriver to release the terminals and pull them from the plug.
With a reproduction wiring harness that is not a sure thing. My Corvette reproduction harness had the leads reversed in the two-plug connection to the fuel gage and I had to reverse them. A new harness in another car I have had a plug with two wires reversed in position. If the leads to the plug are reversed it's pretty simple to use a small screwdriver to release the terminals and pull them from the plug.
I will check the wire connector at the meter-Thank you
A thought, you said "fan" is connected. I assume you have installed an electric fan. You may be reading the draw on the fan if the charging system isn't working correctly. Try disconnecting the fan and see if your needle goes to zero.
Edit: Another thought. Probably not, unless the fan doesn't run until car heats up. You said the needle doesn't move when you turn the key on without starting, so that would test the fan draw with no charging if it runs anytime the key is on.
I should have clarified that it was the heater fan. i apologize.
With a reproduction wiring harness that is not a sure thing. My Corvette reproduction harness had the leads reversed in the two-plug connection to the fuel gage and I had to reverse them. A new harness in another car I have had a plug with two wires reversed in position. If the leads to the plug are reversed it's pretty simple to use a small screwdriver to release the terminals and pull them from the plug.
It seems you were right.I swapped the wires in the connector and my gauge is working. Thanks for your input
Ammeter issue
