6 volt amp gauge or 12 volt amp gauge

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robertwg

Member
Is there a difference between 6 volt and 12 volt amp gauges? They put a cheap after market amp gauge on my 35 and I am trying figure out if its working right. When I turn on ignition it goes to discharge even further with lights and heater motor. Then when I start the car it doesn't come up. When I unhook the output wire off the cutout relay on the gen I get 7 and half volts so gen is working. Don't know if the original works or not they cut the wire and ran it through the after market gauge. It's putting out volts why is this gauge not reading it. How do I check if gauges are bad and is it possible there is a difference in 6 and 12 volt gauges. Also at what rpm should the gen start putting out volts mine seems to have to be up around 1500 rpms.

Thanks Bob
 
The amp meter is showing how much is going in or out of the battery so if youre battery is charged it wont show much.
And amps is amps no matter what voltage so the meter dont care about 6 or 12 volt.
With youre engine off put on the lights and other user if the meter is working it should show disharge.
 
Yes, the gauges are different, at least they should be according to electrical theory. Ammeters aren't scaled to voltage, they are scaled to amperes (even though the gauges don't have numbers on them, but zero is still zero in any case).

A 6 volt system uses twice the amperage as a 12 volt system, which is why the wires are twice as thick. If you install an ammeter designed for 12 volts on a 6 volt system it will swing more widely, but up is still up and down is still down which is what really matters to show you charging and discharging.
 
Might attempt to figure out what is happening at the battery. Check the battery voltage without the engine running and see what it is, should be somewhere a little above 6v. Then recheck it with the engine idling and see if it goes up any and how much. Then check it with the engine revved up a little and see what that is. This should tell you if the generator is charging the battery and at what RPM it is charging. Reading at the battery should be in the 7 to 7.5v range (as you are already getting at the cutout). If everything at the battery checks out there may be a wiring issue at the Amp meter or just a bad Amp meter.

If the battery is holding a good charge you might need to apply a load to see what is going on such a turning the lights on and checking engine off and engine on.
 
Unhooked the wire from the generator on an original 35 Ford generator will make 45-50 volts for a short time---then the generator burns up, or the armature throws the solder, the 3 brush needs the battery to control the voltage

the speed thegenerator starts producing voltage that is useable depends on the size of the pulley and the generator, some were made to charge at low speed

with the generator connected check the voltage on each side of the cutout, as the engine is brought up off idle the "arm" side of the cutout should rise to the voltage on the "BATT" side of the cutout, then as the cutout connects it should stay the same (if it is a doide cutout the "ARM"voltage will stay 1/2 volt more), if the "ARM" side voltage goes higher the cutout is bad

usually the generator should start charging a little bit off idle speed

the "BATT" side voltage should rise above battery voltage, how much depends on the charge rate of the generator, condition and state of charge of the battery and the condition of the wiring
 
You can check current flow with a starter/current tester. They work inductively meaning they just need to be close to the ammeter wire to indicate current flow or charge/discharge. This way you don't have to cut any wires to do the testing.

(Works on the the same principle as the early Ford ammeters that have a loop in the back vice two posts to attach wires to)

Here's a picture of a Snap-on set. I've seen Stewart Warner versions as well. They occasionally come available on online auctions and may be available from different suppliers. I don't know if they are still manufactured as most cars have gone to computer diagnostics vice older methods.

Hope this helps.
 

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