Ammeter not working

[Ralph E.]

What is the best way to check why my ammeter stopped working? I checked the alternator and regulator both are working. If I remove the plug on the back of the ammeter can I test the circuit wiring without damaging anything. What is the best way to test the circuit?

[andy#34338]

Re: Ammeter not working

You can check it using a watch battery.

[andy#34338]

Re: Ammeter not working

You can check it using a watch battery.

[Gary S.]

Re: Ammeter not working

I also believe that you can put an ohm meter across the terminals to check for a burned wire. My friend's 73 had no continuity across the two terminals so we took it apart VERY CAREFULLY and found a burned wire. With nothing to lose, we took notes of its construction and slowly unwound the wire. We measured the wire and then took the green coated wire, as a sample, to Radio Shack and matched it exactly. We re-wound the wire, reinstalled the needle, glued the case back on (had to cut off the tiny rivets) and installed it in the car. It is still working six months later.

As a side note, if you chose to go this route, note not only the length of the wire but in what direction it is wound and the sequence. It took us longer to take the notes than it did to repair the meter.
Gary

[Gary S.]

Re: Ammeter not working

I also believe that you can put an ohm meter across the terminals to check for a burned wire. My friend's 73 had no continuity across the two terminals so we took it apart VERY CAREFULLY and found a burned wire. With nothing to lose, we took notes of its construction and slowly unwound the wire. We measured the wire and then took the green coated wire, as a sample, to Radio Shack and matched it exactly. We re-wound the wire, reinstalled the needle, glued the case back on (had to cut off the tiny rivets) and installed it in the car. It is still working six months later.

As a side note, if you chose to go this route, note not only the length of the wire but in what direction it is wound and the sequence. It took us longer to take the notes than it did to repair the meter.
Gary

[Donald O.]

Watch Battery?

Andy,

How do you check it with a watch battery? Would this trick work on a '67?

Don

[Donald O.]

Watch Battery?

Andy,

How do you check it with a watch battery? Would this trick work on a '67?

Don

[Ralph E.]

Re: Watch Battery?

Thanks everyone. I didn't try the watch battery. What I did was check the continuity in the wiring circuit to the ammeter. That confirmed I cleaned the terminals on the back of the ammeter and the wire terminals on the connector. I then reconnected the ammeter. Then reconnected the battery. Turned on the lights and the ammeter dropped. I only hope it was this simple. Prior to any of this the gauge didn't move.

[Ralph E.]

Re: Watch Battery?

Thanks everyone. I didn't try the watch battery. What I did was check the continuity in the wiring circuit to the ammeter. That confirmed I cleaned the terminals on the back of the ammeter and the wire terminals on the connector. I then reconnected the ammeter. Then reconnected the battery. Turned on the lights and the ammeter dropped. I only hope it was this simple. Prior to any of this the gauge didn't move.

[andy#34338]

Re: Watch Battery?

Don,

You use the watch battery as a power source for the meter. It will read the voltage. If you try to use 12v it will fry.

Andy

[andy#34338]

Re: Watch Battery?

Don,

You use the watch battery as a power source for the meter. It will read the voltage. If you try to use 12v it will fry.

Andy

[Michael W.]

OK, how many amps is 1.5 volts?

I think you are confusing amperes with volts

[Michael W.]

OK, how many amps is 1.5 volts?

I think you are confusing amperes with volts

[Jack H.]

Circuit topology....

There's a thread of truth here (watch battery) and the confusion flows from understanding how the ammeter circuit works. The ammeter is placed in parallel to a given/known point of battery current flow. This makes it a 'shunt' circuit, meaning it watches/monitors a CONTROLLED FRACTION of the car's battery current flow.

Heavens if the ammeter were tasked to sit 100% in-line to the battery, the wires connecting it would have to be the sized of the battery cables themselves! You know this isn't true.... Very small 18-20 guage wires connect to the ammeter.

So, by cutting the voltage of a test source down (12V -> 1.5V; about a 10:1 reduction), the suggestion is VALID to grossly exercise the ammeter without burning it up!

In the car, the 'shunt' circuit divider action is performed by controlling the relative resistance of wiring runs to scale the current flow readings. Which is why one of the first suggestions in troubleshooting is to review all pertinent connections for clean non-oxidized ohmic contact state....

[Jack H.]

Circuit topology....

There's a thread of truth here (watch battery) and the confusion flows from understanding how the ammeter circuit works. The ammeter is placed in parallel to a given/known point of battery current flow. This makes it a 'shunt' circuit, meaning it watches/monitors a CONTROLLED FRACTION of the car's battery current flow.

Heavens if the ammeter were tasked to sit 100% in-line to the battery, the wires connecting it would have to be the sized of the battery cables themselves! You know this isn't true.... Very small 18-20 guage wires connect to the ammeter.

So, by cutting the voltage of a test source down (12V -> 1.5V; about a 10:1 reduction), the suggestion is VALID to grossly exercise the ammeter without burning it up!

In the car, the 'shunt' circuit divider action is performed by controlling the relative resistance of wiring runs to scale the current flow readings. Which is why one of the first suggestions in troubleshooting is to review all pertinent connections for clean non-oxidized ohmic contact state....