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Did you already buy the amp gauge? If not put in a volt gauge, easier to hook up and virtually the same information in my opinion.
 

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If you already bought it....... return it ........ Volt meter is easier to install and much safer.
 

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Ditto to what the guys above have said! You really don't want an amp meter. :sad:
 

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A volt meter has two lugs on the back and another wire.
One lug goes to ground and one lug to 12 volts. the 3rd wire goes to a power source that is hot when your dash lights are on.
A amp meter the 12 volts goes through the gage. 12 volts in and 12 volts out. Usually out from the alt and on to the car. The 3rd wire goes to dash lights.
 

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Discussion Starter · #6 ·
I just happened to have an old VDO amp meter that I thought I would put on. So you guys think a volt meter would be better? I just want a meter that will keep me informed whether or not the battery is charging. I have not had any problems I just like to have a guage is all.
 

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A voltmeter is a parallel device while an ammeter is a serial device. This means the ammeter must be in serial with all loads. For an automotive application this results in having rather large wires making a long run.

To wire an ammeter you will need two 8g wires running from the meter in the dash up through the firewall, along a fender, and splicing into the 10g wire that feeds from battery to horn relay (they did have those in '66 didn't they?). The way I would do this is to pick up a mega fuse block from American Autowire and mount it up on the core support next to the bulkhead connector GM put there. I would run the battery positive to one side of the fuse block. I would run the other side of the fuse block to the ammeter. And finally the second side of the ammeter to the GM bulkhead connector. This would avoid modifications to the factory harness as well as provide electrical protection to the long ammeter wiring.

Note that this actually might not be too bad... this portion of the electrical system only carries current either when the engine is not running or for charging the battery. This reduces the current load and helps reduce voltage drop.

A voltmeter is much easier to wire though and can provide similiar information if you know how to interpret it.
 

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I know you know this Steve, probably just a slip of the tong/fingers. Parallel and serial are ways to pass binary data. An ammeter is a series device.

Yes 66 has the 10 ga wire from the J-block to the horn relay.
 

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There are a couple of primary factors here...

First and the biggest is the exposure of running some fairly large wire across a fairly large distance. The risk of shorts of course increases as you go further. This can be mitigated by appropriate fuse or circuit breaker protection.

Next are the connections that are typically needed. More connections mean more potential failure points for a critical element in the electrical system. This especially becomes true as current flows are increased, which a 10g wire can support, but see below.

And finally the voltage drop which may result from the extended power feed wiring. Now this one may not be quite as big a deal as many make it out to be. If set up right, during normal operation this wire may carry very little current at all. And that will go a long way to minimizing voltage drop.

An interesting debate could be had on the relative merits of the diagnostic capabilities provided by an ammeter versus a voltmeter. For a basic charging system go/nogo test both function just fine. And then they diverge...

An ammeter tells you if and how much current is flowing into or out of the battery. This in turn tells you if the battery is charging as expected or discharging. Discharging would indicate no or low alternator output and send you to the garage. Further knowing the amount of flow better allows you to manage the battery capacity when failure occurs. Turning off devices is visible and the amount of flow provides some rough idea how long the battery power may last.

A voltmeter tells you how high the voltage is in the system. Which can actually tell you quite a bit IF you understand how things work. The battery normally provides somewhere around 12.5v when fully charged and this voltage drops as the battery becomes discharged. The alternator, through the magic of the regulator, normally provides around 14v. Thus you can deduce that at voltages above 13v the battery will be charged and below 12.5 the battery will start to discharge. But you can also tell if the regulator fails and allows the alternator lock on and raise voltage too high. This can be bad for battery life as well as other electrical devices. You cannot tell this from an ammeter. And if you understand the voltage drop versus battery charge, you can estimate remaining battery charge too.
 

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the volt meter is easier to glance and and get a good reading. if it usually runs at 14 volts, and suddenly it reads 12 volts, then you know you have a problem. the ammeter migth only move a little bit off the center mark, and wouldn't be as visible at a quick glance.
 

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simply put...9 times out of 10, an ammeter creates more problems than it solves.
 
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