12v amps gauge
 

can I use a stock 6v amps gauge in 12v neg ground system?

Re: 12v amps gauge
 

Yes, reverse connections for neg ground.

Re: 12v amps gauge
 

Yes, although if your going to run a high current alternator you may want a shunt across the ammeter to reduce its throw. Overdeflection will kill the ammeter. An original ammeter is not something you want to waste, the repros aren't so good.

Re: 12v amps gauge
 

ok reverse wires. alternator goes to +?

Re: 12v amps gauge
 

Using a shunt across the ammeter pretty much makes the amp gauge non responsive.

Re: 12v amps gauge
 

Facing front of ammeter, stock battery wire (yellow) goes to right side, generator wire (yellow-black) to left. Reverse those for negative ground.

Forget a shunt. Just makes normal battery current hard to read. Use common sense instead:

Sure, if you switch on your Blazing Baja Beams and Behemoth Boom Box with the engine off, you'll likely peg the meter into the Far Far West.

Don't do that.

Re: 12v amps gauge
 

Current draw out of the battery and charging current should be less on a 12 V system compared to a 6 V system. Assuming all the loads (horn/starter, lamps, etc) are proper for a 12 V system.



So the gauge should be OK but most likely will read less. The gauge does not care what the battery voltage is, just the load/charging amperage.

Re: 12v amps gauge
 

Most alternators will put out at least 35 amps immediately after starting.
Install an aftermarket ammeter from Model A parts dealer with 30/30 reading.
They look just like the 20/20 original except the higher amp readings.

Re: 12v amps gauge
 

To the OP: I agree with Badpuppy's comment, it is possible to use the stock 6 volt ammeter in a 12 volt system by reversing the leads.

This is off topic somewhat: I installed an AC unit in a recent build of a touring car. Every time the AC compressor clutch would engage, the needle would peg...hard. After a few days, the needle disappeared as it was knocked right off the pivot points. I did not know what size shunt to install so I installed a second ammeter under the hood to split the load. Both meters show a good draw when it starts...just short of pegging but so far, I have not lost sight of anymore needles.
Anyone have a guess of what size shunt is needed based on my description? Thanks Guys.
Good Day!

Re: 12v amps gauge
 

Agree with Dave-in Minn. The current draw of a AC is almost constant load of 25/30 amps depending on the AC clutch cycling. That continuous load will cause the 30 amp meter to get hot because it is at the top of the load rating. On a cross-country road trip one of our cars, AC equipped, burned the amp meter up. Mine got very hot to the touch. I made a temporary shunt using 6 foot #16 wire wrapped around a 3/8 dowel approx. 3" long. It works well. First start of the engine the amp meter indicates about 5 amps charge very briefly.

Am experimenting to create a shunt that will indicate a charge of about 10/15 amps with full AC and Headlights load. If you have already done this please message me.

Re: 12v amps gauge
 

You need to increase the resistance of the shunt so more goes through the ammeter. The ammeter gauge in my '32 reads almost exactly half so I just remember to double it. See photo. If I was doing it on my Model A where there is less room I would just run a second wire of the same gauge from the output of the generator or alternator to the opposite post on the ammeter.

Charlie Stephens

Re: 12v amps gauge
 

The ammeter shows the amps that the generator is putting out , not the voltage . I use the same ammeter with 12 volts that I use with 6 volts . The original unmodified generator will charge a twelve volt battery with no problem . I use the Fun Projects 12 volt voltage regulator that takes the place of the cut out . As has been said , the generator doesn't know the difference because the generator charges in amps . Generator out put can be controlled by the adjustable brush in the generator . Pushing the adjustable brush downward toward the ground raises the amperage out put . Raising the adjustable brush upward decreases the amperage out put . I have used the 30 amp ammeter when using the 60 amp alternator just for good measure . High amperage out put charges the battery quicker . A voltage regulator , when used prevents overcharging the system .

Re: 12v amps gauge
 

I never need a shunt .

Re: 12v amps gauge
 

Use nichrome wire to make an ammeter shunt. A good original ammeter is something you don't want to ruin. Size the shunt for the deflection you want, use an inline ammeter to give you the calibration factor.