Amp gauge Inop - Team Camaro Tech
Electrical & Wiring Troubleshooting electrical.

 
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post #1 of 9 (permalink) Old Jul 6th, 00, 11:16 AM Thread Starter
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My amp gauge appears to be inop. It is always centered and never moves even when the battery was dead and then fully charged. My question is what's the best way to test if it is the gauge. I understand these work on differential voltage so it seems like you could just measure to see if it is getting voltage at each terminal. Any recommendations on how tom test this would be appriciated.
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post #2 of 9 (permalink) Old Jul 6th, 00, 06:11 PM
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I'm guessing that the amp guage is measuring volts from two parts of the wiring harness and is scaled in amps.
It might be that you have a bad ground and this is causing no reading. Or you may have a bad connection from either lead from the wiring harness.

I'd measure volts from both leads from the wiring harness and compare readings. I'd also use a jumper to give a good ground to the amp guage to test for ground.

I haven't had to do this so it's a guess.
It seems like years ago I fiddled with a chevy pickup amp guage and it had a fuse at one end up front in the harness. If you get no reading on one side you might look for a fuse. It might be in the fuse panel on a camaro, but the one I found was up front.
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post #3 of 9 (permalink) Old Jul 7th, 00, 06:31 PM
 
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Most ampmeters measure current in line with a conductor. (The current actually passes through the gauge, the gauge does not merely measure the current). After you verify that your fuses are all good the best way to tell if your vehicle gauge is malfunctioning is to put a known good ammeter in its place (any multimeter will work). [A word of caution is in order- if you have any doubt about what you're doing, stop. This is not an area to play trial and error, because errors can mean significant electrical damage.] I dare say however that it's a good bet that your factory gauge is dead (assuming the fuse is good). I think that most speedometer shops can repair factory ampmeters.
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post #4 of 9 (permalink) Old Jul 8th, 00, 08:43 AM
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I just checked one of my old textbooks. The aftermarket type ammeters pass the load through a "shunt" usually mounted to the back of the guage. The shunt carries the heavy load and the guage is attached to each side. The guage reads the voltage difference between each side of the shunt and reads out in amps.

The factory type guages use the cars wiring harness as the shunt. So any extra resistance in the guage side of the harness would tend to deaden the ammeter.
You could have an internal problem with the ammeter too.
The other guages are powered by a low voltage regulator circut.
David

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post #5 of 9 (permalink) Old Jul 8th, 00, 02:49 PM Thread Starter
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Thanks for the help guys, but this is the original stock amp meter and I believe these run off of differential voltage. I think my best plann is to measure the voltage at both terminals and see if there is anything there. I'll keep you posted as I have never had to trouble shoot one of these.
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post #6 of 9 (permalink) Old Jul 8th, 00, 03:00 PM
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On my 70 the wires run from the gauge out to the regulator/horn relay area. They have fusible links on the ends at the front. My front wiring has been changed over the years so I don't know for sure how it's supposed to work. Been looking into this myself. I assumed the gauge carried the current to and from the system to the battery. Originally this would be no more than 35 amps or so, today with added electrics it might not handle the current if it does actually handle the load. Still looking, really need an original wiring diagram to figure it out I guess.
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post #7 of 9 (permalink) Old Jul 8th, 00, 04:02 PM
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I'm presently replacing the idiot lights in my 67 with a ralley gauge package from a Firebird. To make my Amp gauge swing full scale it took 0.61 volts. I'm going to set my conversion up so full scale is about 60 Amps. This means I need a 0.01 ohm shunt to make my ampmeter work. Thats about the resistance of a 5' piece of 12 GA copper wire. Tomorrow I'm going to install the gauge. I'll let you know how it works out.
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post #8 of 9 (permalink) Old Jul 10th, 00, 05:33 AM
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i spent about 2 months trying to figure out the same trouble on my 69...the meter IS voltage sensing of the differentila of the alternator output and the battery.... mine only moved silghtly,,, too little to even read,,,, when my console lights finally went out and I repaired the loose ground wire inside the console, the "amp" guage started working.... I still haven't been able to find a wiring diagram for the internal workings of the guage to see how the ground affects the workings BUT it did apparently...... or else there is another loose wire that I wiggled.... GOOD LUCK

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post #9 of 9 (permalink) Old Aug 11th, 00, 04:59 PM
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Hey ampmeter experts. I have the oposite problem the originator of this subject has. I have an over active ampmeter. The alternator puts out current, the battery is charged, but the ampmeter keeps bouncing between various stages of "charge" and dead center. I've replaced the regulator and alternator, checked the grounds in the engine compartment, but still no luck. The car turns over and runs fine. I would think if I did have a charging problem, I would have a hard time keeping the battery charged. Any thoughts? What role might the horn relay play, as it seems to be a major link in the power chain? This is in a '69.

Thanks!

Keith
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