1971 amp guage
Team Owner
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From: Orange Park Florida
Le Mans Master
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From: Chattanooga TN
The ammeter cars use a shunt type system, they do not use a ground like a voltmeter does. The shunt wires are in the 2 engine compartment harnesses. You really need a good wiring diagram to troubleshoot this.
Race Director
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From: Foxfield CO 1970 Convertible
OK - related question...Can anyone point to or describe a detailed method to check the output of the alternator using a DVM or similar? That way someone can tell whether it's the gauge or the alternator...
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Instructor
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From: round rock tx
Gene? measure voltage?
Thanks Gene,
The alt measures 14 volts at 2000 rpm. It would be very difficult to connect anything to the amp meter unless I take the console out?
Or would it?
larry
The alt measures 14 volts at 2000 rpm. It would be very difficult to connect anything to the amp meter unless I take the console out?
Or would it?
larry
Le Mans Master
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From: Boca Raton Florida
check the voltage output at idle with everything off, then turn everything on and check it again. Idle should be about 13.8 or better with everything off and better than 12.5 with everything on at Idle, at 2000 you should get 14.x with everything on
Team Owner
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From: Crossville TN
First, make sure your alternator connections are good. The connectors can come loose or get tarnished to a point that the circuit drops. If that is not the problem then turn on your headlights/brights without starting the car. The ammeter should read negative current. If it doesn't move, either the meter is bad or the wiring to it is bad. NO GROUND PROBLEMS POSSIBLE. If you didn't have an electrical "event" [inadvertant short, etc.] it is likely your meter went "south". Usually, this is because of one of the lead wires [internal to the meter] melting or breaking. Once you have tested to be sure that it is the meter, remove it from the dash and take the housing off. Check the lead wiring. If one is broken, use a small pencil-type soldering iron to bridge the break or re-solder the lead. It should be fine. If you did have an "event", you probably melted one of the fuse-link leads in the ammeter circuit. Find the damage and patch it up. Good luck! 
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Race Director
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From: Foxfield CO 1970 Convertible
At what points do you measure the voltages?
Le Mans Master
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From: Boca Raton Florida
Measure at the alternator output to check the alternator. If you want to check at the battery that would be a good idea, record all your reading and under what conditions. this will allow you to see whats going on all over the car
Race Director
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From: Foxfield CO 1970 Convertible
) I've relied on the dash gauge for general readings, but it would be interesting to try and correlate a position on the gauge with the actual voltage.
Le Mans Master
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From: Boca Raton Florida
Your going to be measuring VOLTS on the back of the alternator not AMPS. Voltage is measured across a circuit and amps are measured thru a circuit
So no worries frying your meter with it on the 20 volt scale
So no worries frying your meter with it on the 20 volt scale
Race Director
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From: Foxfield CO 1970 Convertible
)
Advanced
Joined: Apr 2006
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From: Finly IN
Inop Ammeter
I also have bad ammeter indications on a 1975 Vette. The ammeter is good. (Full scale deflection +/- when 1.5 vdc battery is placed across terminals and then reversed)
black wire - Have battery voltage on black wire. (I assume from horn relay).
Black w/white tracer - no voltage. Can't seem to get continuity check or locate other end? Where does this wire go?
Can anyone supply a simplified electronic diagram with location of connectors?
Thanks for the thread - very timely.
I'm making progress.
black wire - Have battery voltage on black wire. (I assume from horn relay).
Black w/white tracer - no voltage. Can't seem to get continuity check or locate other end? Where does this wire go?
Can anyone supply a simplified electronic diagram with location of connectors?
Thanks for the thread - very timely.
I'm making progress.
Le Mans Master
Joined: Jan 2006
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From: Boca Raton Florida
RAD, your gonna need a good schematic for a 75, I don't know where exactly where the wires go. But if you have no voltage on the black/white wire it would seem you have found the problem. An amp meter works by measuring the voltage across a known resistance (wire in our case). PO may have disconnected it or something. I don't particularly care for ZIP, but they do have a colorized ilustrated schematic for your year. Check it out, it may give you the hook up you need
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Instructor
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From: round rock tx
I purchased a large wiring/vacuum diagram for the garage wall from Don Olson Engineering in Ohio. The diagram will be for year of car with the accessories you have (ps, a/c, etc.).
It has worked great with the electrical problems I have had.
It has worked great with the electrical problems I have had.
Last edited by larry hinterman; Jan 13, 2007 at 08:18 AM. Reason: spelling
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Instructor
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From: round rock tx
Amp meter wires - two:
The wiring diagram shows that:
One. No. 16 black connects to the firewall bulkhead connector. Then comes out as blk to red and connects to the red wire that goes between the horn relay and the starter on the S connection.
Two. The 16 blk-wht-dbl turns purple then black and connects to the black wire from the console ground and then runs to the dash cluster lamps connection, where the wire goes to all of the lamps.
The fuse panel diagram shows that there are not any black wires comming out of it to inside the car.
The wiring diagram shows that:
One. No. 16 black connects to the firewall bulkhead connector. Then comes out as blk to red and connects to the red wire that goes between the horn relay and the starter on the S connection.
Two. The 16 blk-wht-dbl turns purple then black and connects to the black wire from the console ground and then runs to the dash cluster lamps connection, where the wire goes to all of the lamps.
The fuse panel diagram shows that there are not any black wires comming out of it to inside the car.
Last edited by larry hinterman; Jan 13, 2007 at 12:11 PM. Reason: additional info
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From: Finly IN
Awesome
Larry,
Thanks. Awesome information. I'll take your tip on getting a good wiring diagram. They (GM) would have never got away with that in aviation/aircraft wiring.
The last thing to fix was before installing the radio was the ammeter. After that the interior is almost done except for nickel dime stuff. I didn't want to lose the weekend and holiday. I can have this done today with the information you supplied. The only problem I see is the Indy colts game this afternoon being a distraction.
Ralph
Thanks. Awesome information.
I'll take your tip on getting a good wiring diagram. They (GM) would have never got away with that in aviation/aircraft wiring. The last thing to fix was before installing the radio was the ammeter. After that the interior is almost done except for nickel dime stuff. I didn't want to lose the weekend and holiday.
I can have this done today with the information you supplied. The only problem I see is the Indy colts game this afternoon being a distraction.Ralph