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Has anyone used a shunt for the ammeter? I have got an electric fan, halogen headlamps, electric fuel pump, 400 watt stereo, etc. and the existing aftermarket ammeter that I had installed, is definitely not an option. My throughts were either to install a shunt, or go with a voltmeter.

Thanks in advance for your ideas, experiences...



Steve Leslie, 65 coupe in restoration. 302, toploader, A/C, disc brakes, bench seat

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Hi Steve -- I converted to a '66 dash which uses a shunt type ammeter. I am considering one of the high output one-wire alternators but no one seems how to wire the ammeter. So if I make that change I'll probably modifiy an old ammeter I have to operate as a volt meter. I think a volt meter is a better idea anyway. My dad's Chevy truck uses a volt meter rather than an ammeter. And in theory what's important is what's going back into the battery anyway. With a volt meter you can see that. I have had a bad regulator but a good alternator and wound up with a dry battery while the ameter showed normal.

...modified '65 convertible...
 

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Not recommended for the faint of heart. The ammeters in mustangs rely upon a very small difference of resistance between two parallel paths from the alternator to the battery side of the solenoid switch. It's the difference between (I'm making the exact numbers up) between 0.10 ohms and 0.13 ohms, with the higher resistance the ammeter circuit. You can do it, but you'll need a variable power resistor of very low resistance to adjust the circuit so that the ammeter won't go full scale on you. In addition, Ford neglected to fuse the ammeter, and it does burn up at times, setting cars on fire (don't ask, and I won't tell!).

I agree with the other poster: convert to the voltage meter, as it actually is more useful as a diagnostic tool.

http://clubs.hemmings.com/baymustang/platesmall.jpgLet me check your shorts! My multimeter is just a-waiting! Formerly known as Midlife in the old VMF.
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A volt gauge is the only way to go. I have one in all of our daily drivers (3) and the
track car. Having the big alt. wire run in the car and back out again is just asking
for trouble. I have seen more than one car fill with smoke from the wire on a amp.
gauge rub through and short out. You can hook up the volt gauge to any 12V source
inside the car.
 

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wire 38A is actually a shunt on my '68 that goes from solenoid batt term to alt output. this is a weird way to put in a shunt which is usually on the back of ammeter but it works and provides protection for the meter if you inadvertently short out ammeter term which hangs in series between alt and batt - that is why so many burn up violently. do not know when this change was put in since i believe earlier cars did not have shunt. this shunt is nothing more than a low resistance wire across ammeter between solenoid batt term and alt output. i tore all my tape off my harnesses to validate this since i couln't believe it.
 
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