Here it is guys, there is NO SHUNT used in the wiring of the amp gauge on a 67 chevelle. I believe that would be true for all 64-72 chevelles. The tried and true set-up I have found is to hook the black w/white stripe wire from the gauge to the BAT terminal on the horn relay, the black wire from the gauge goes to the terminal block on the radiator support behind the battery (or to the + terminal on the battery). I installed a in-line fuse on both of these wires (1 amp) under the hood. I ran new (18 ga.)wires because I could not find them both in the engine harness. I now have all my gauges working again!!

I am glad to see someone else use an in line fuse to power an amp gauge. Most of the info says to use fuseable links to protect the wiring and prevent fire in case of a short -good idea but the amp gauge only pulls about 2 amps to registor +/- 40amps. The fuse will protect the wiring and your gauge and in the case of 70-72 the circuit board(how many of these have you seen blown) on the gauge panel. 1 amp may be a little low, my bench testing has shown that the gauge draws about 2 amps to register 40 amp charge or discharge. If either wire gets shorted you will draw massive current through the amp gauge and it will give before a fuseable link will. I put a 20 gauge fuseable link on one wire and a 2 amp in line fuse on the other.

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Steve Strasemeier (70SS 396, Fathom Blue/White Stripes)
My 70SS (http://www.members.home.com/txss/sshome.htm)

Thanks for the amp draw info Steve! I'm going to leave the 1 amp fuses in place for now, if they blow I will probably step-up to 2 amp fuses. Don't think I'll see a 40 amp draw from my car unless there is a short or something fails with the alternator.

The wire from the junction block to the horn relay is the "shunt". Any wire has resistance and that's all a shunt is, a small resistor. Depending on the "full scale sensitivity" of the voltmeter you use, you can easily sense current in a piece 10 gauge wire one inch long. So, although there is not a "physical" part labeled shunt in the wiring harness, the wire is it! True shunts are typically in the range of .001 to 1.0 ohms and that piece of wire easily falls in that range.

David is right on. An amp gauge is a voltmeter reading the voltage drop across a know resistance. In this case a length of factory wire of know length (resistance).

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Steve Strasemeier (70SS 396, Fathom Blue/White Stripes)
My 70SS (http://www.members.home.com/txss/sshome.htm)

Thanks for the responses guys !! I understand that the wire acts as a shunt, I just wanted to point out that there wasn't any physical shunt mounted somewhere under the hood (as I was told). For a while now knowone could come up with the proper wiring of the amp gauge and I just wanted to pass it along.

That's good info, guys.

In the oilfield I've seen lots of shunt ammeter applications on crewboats. Those shunts are basically a copper bar across two terminals.

We also use shunts to measure current across our electric brakes in an effort to prevent overheating from applying excessive current across the coils for too long.



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My Elky Page (http://www.geocities.com/chadjlandry/index.html) (updated 5-15-01)
"Think for yourself. Don't let popular opinion make your decisions for you."
Chad Landry
TC Member #643
ACES Member #04556
'68 El Camino

A good source for a "fused" ammeter circuit is a '67-'72 Chevy pickup with factory guages. These trucks use two small fuses in the ammeter circuit. The wires are black and black with a white tracer and are locted in the harness that runs from the voltage regulator across the core support to the battery.
I think I'll strip one of these circuits and try it in a '64 Chevelle guage setup. Will this work????

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Tim
'57 210 2Dr Wagon
'67 300 Deluxe 2Dr Sedan
'72 SWB Orig 402
'81 El Camino TPI 4-speed

The amp gauge wiring is shown in the early 66 service manual wiring diagrams. The 2 wires are side by side at the bottom of the lamp wire harness plug at the firewall. It shows 20ga for under dash and 14ga under hood. Wires terminated as you indicated.

Rene
66_Malibu