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AMP GAUGE not working

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Old 09-29-2008, 04:50 PM   #1
CF Senior Member
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Member Since: May 2006
Location: Redding CA
Default AMP GAUGE not working

My Question is this...
Does the voltage regulator have "ANYTHING" to do with this problem of the gauge not moving???
I am at my wits end...There is power to the gauge...the B/W and B wires have power...when a continuity is run...we get a reading showing that it is supposed to be working....

Any help or advice would be greatly appreciated

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Old 09-29-2008, 05:38 PM   #2
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Member Since: Nov 2000
Location: Going too fast over the hill.

If it's in a c2, No.

the c2 battery meter is a simple galvanometer that acts as an ammeter by using part of the wiring harness for a shunt.

If the terminals of the meter each have ~12-13volts all the time, the meter will stay centered. Whenthe car runs, the line from the horn relay should apply a higher voltage to one terminal of the battery meter and force a deflection. If you are testing voltages at the meter terminals, and you see a voltage difference, but the meter needle doesn't deflect, the meter has a problem.
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Old 09-29-2008, 06:31 PM   #3
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Member Since: Apr 2005
Location: Luling Louisiana


The AMP gage measures the difference in voltage between the alternator output and the battery. This voltage difference (typically 0.1 to 0.5 volt or so) is a function of the current that the battery is receiving from the alternator or supplying to the car to operate the coil, lights, etc. A specific gage and length of interconnecting wire is used. I believe it is either #10-12 gage.

The AMP gage sensing points are the orange fusible links in the alternator wiring NEAR the regulator and at the starter solenoid battery
terminal. There is also an orange fusible link in the regulator connector harness, but this is used for regulator operation/function and not for the AMP gage. Since I only have a 1967 wiring diagram, I used it for this information...but 1966 should be the same or similar.

Get a good multimeter (Fluke or equivalent) and measure the voltage difference at the alternator ouput terminal and at the starter solenoid battery terminal under a few different operating conditions. Also check these readings against the voltage readings at the AMP gage itself. They should be the same. That should tell you what the problem is: gage or wiring.

You can also remove the wires from the AMP gage and hook up a 1.5 volt battery across the gage terminals. The gage needle should move significantly. Then reverse the battery connection and the gage should move in the opposite direction.

You could have a bad gage, or the gage wiring could have corrosion at the two attaching points or at the firewall terminal (fuse) block. Let us know what you find.

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Old 09-29-2008, 08:06 PM   #4
George Tavary
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Member Since: Jan 2005

I had same problem with my 66 and found bad connections at the firewall terminal
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Old 09-30-2008, 04:21 PM   #5
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Member Since: May 2006
Location: Redding CA

i will let you all know when i find the problem...thanks to those that replied with some direction for me to look...

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Old 10-02-2008, 03:08 PM   #6
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Member Since: May 2006
Location: Redding CA


anymore suggestions???
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Old 10-02-2008, 06:31 PM   #7
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Member Since: Jun 2006
Location: SF Peninsula CA

The amp meter in mid years, really isn’t an amp meter, but a voltage meter (with 0V at center scale). It measures the voltage drop across wire 10R, which travels from the starter solenoid to a junction with 20R 14R and 12R (at the horn relay). This wire has a specific resistance, the greater the current, the higher the voltage drop across it. The amp meter (volt meter which measures this small voltage across 10R) indicates estimated amperage through 10R. This meter measures small voltages and is easy to fry. First thing is to see if the meter is still working, and can be done with a flashlight battery. Unplug the amp meter, attach test leads to meter and a 1.5V flashlight battery. You should get a deflection. Reverse connection to battery and you should get a opposite deflection. This will tell you your meter is working, or not.

In stock form, when the key is turned on, current flows from the battery through the battery cable to the solenoid, through 10R to the junction on horn relay, and as soon as the motor starts the alternator now supplies power to the junction. Current will now flow the other direction through 10R to charge the battery. If 10R is replaced with a larger gage wire or bypassed in any way (I have read that some people install a wire directly to the positive post of the battery), Your Amp meter will not work as designed.

Last edited by lcpaca; 10-02-2008 at 06:57 PM.
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Old 10-03-2008, 10:30 AM   #8
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Member Since: Nov 2000
Location: Going too fast over the hill.

OK - you want a step by step procedure?

1 disconnect the battery ground.

2 connect 2 shielded jumper wires to the Battery meter terminals, one to each terminal - and let the ends hang to the floor of the car.

3 reconnect the battery ground.

4 connect a ($4 at Harbor Freight) multimeter in 0-20volt mode to one jumper wire end and the other to ground (e.g. the instrument cluster) to get a reading of about 12volts.

5 disconnect the multimeter from that jumper lead and connect the other jumper to get a 12volt reading there too.

6 If you do not get a reading of approximately 12volts from either jumper, the wire that doesn't have 12volts is not connected to the horn relay or the starter solenoid. Find the break in the connection to the Battery meter.

7 if both sides have a reading of about 12volts, start the car and check the readings at both jumpers again (steps 4 and 5). One of the jumpers (the one connected to the wire from the horn relay) should read higher than the other. If it does, and the meter does not move, replace or repair the meter.

8 Post here again to tell us the results.

PS: if the meter is damaged, and you are installing the repaired/replacement, you may want to install a 1 or 2 amp inline fuse on one of the terminals as noted in the help area near the bottom of this web page:

Last edited by magicv8; 10-03-2008 at 10:48 AM.
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Old 10-03-2008, 10:30 AM
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