Amp Gauge - C2

[Larry S.]

My amp (I know, its actually a volt gauge) on the dash doesnt show any movement at all. I want to connect a tester (Volt) across the two terminals to take a reading. Do I need to disconnect the wires to the gauge first and connect only to the two wires, or just clip on the two terminals on the back of the gauge - wires still connected?
I have checked the firewall connections and the blocks are all new.
Thanks.
PS. I tested the voltage output with a tester that goes in the cigarette lighter and it reads 13.9 - 14 Volts after the engine has been running for at least ten minutes.
Thanks for any help.

[Jack H.]

Re: Amp Gauge - C2

You're on the RIGHT track in diagnosing the fault! You've done decent due diligence to verify the charging system IS working by monitoring the car's B+ voltage rises above normal levels to the +14 VDC range with the engine running. EXCELLENT!

Now, on checking at the ammeter itself, you CAN use a voltmeter to measure the potential difference across the driving terminals, but expect it to be pretty darn low. As you said, you understand the dash ammeter is actually a voltmeter measuring MINOR voltage difference(s) between two points in the wiring system.

A decent check is to disconnect the ammeter and use a standard AA 1.5 VDC battery to 'drive' the gauge. MOMENTARILY connect the battery across the terminal on the gauge and verify that it will BREIFLY switch it each direction with the battery connected in one then the opposite polarity. That gives you a gross functionality test of the meter itself.

Once you see the gauge actually works, it's then a matter of working backwards through the wiring system to see why you're not getting voltage differences on the two connecting wires.... Have fun!

[Larry S.]

Re: Amp Gauge - C2

Thanks Jack I'll give it a try !

[Rich G.]

Re: Amp Gauge - C2

I posted a similar question a while back. My 66 amp gauge hardly moves but I know the charging system is working fine. In fact my battery is 5 years old and going strong.

At that time a few guys with 66 cars told me theirs did the same thing. One poster at least said his did it since it was new.

Rich