32 ammeter

[Ken/Alabama]

Running a power gen alternator through a original 32 ammeter. When it's charging it almost pegs the gauge. Is this a bad thing to do this? System has been changed to 12 volt.

[deuce lover]

Is your batt charged full? In my '33 I have a 12V 100 amp alt and stock amp gauge.Batt is brand new .Needle only goes up to approx 5-7 on the gauge.My gauge has the 2 studs on the back and not the loop.

[Ken/Alabama]

Originally Posted by deuce lover

Is your batt charged full? In my '33 I have a 12V 100 amp alt and stock amp gauge.Batt is brand new .Needle only goes up to approx 5-7 on the gauge.My gauge has the 2 studs on the back and not the loop.

Yes, this one has two studs not a loop. Just didn't want to cause damage to the gauge or something getting hot and causing a fire. This car has an electric fan and when it kicks on the ammeter goes way over.

[flatheadmurre]

The loop type isn´t that sensitive to overloads.
The type with screw posts have an internal resistor that heats up being overloaded and can start a fire being badly abused...
I agree with Deuce lover that the charge should drop after a while if the battery is in good shape...
If the ammeter shows the load of the fan it´s not installed correctly.
The ammeter should only show what goes in or out of the battery.
You should move the connection of the fan to the generator side of the ammeter.

[Charlie Stephens]

Here is a picture of the shunt I used on my '32 amp meter. If I was doing it again I would run two identical wires from the generator (alternator in your case) to the amp meter. One will be attached to each side of the amp meter. I will use the same gauge wire so the reading is cut in half and in case of a failure the remaining wire will be large enough to carry the load. The amp meter reading is cut in half which is what I wanted.

Charlie Stephens

[Bored&Stroked]

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Good idea Charlie! I have a converted generator by Whitney - it puts out more amps than the amp meter can register, though only for a brief period after I start the engine. I still like the idea that Charlie (and others)talk about - maybe I'll add the shunt to reduce the load going through the gauge - seems to be a good thing to do.

[JSeery]

As flatheadmurre posted, is the ammeter wired so all it is seeing is the current going to and from the battery? System loads shouldn't show a large increase in amperage flowing to/from the battery, and even if it did it would be showing a discharge because of current flow from the battery. A heavy current loads through a terminal type ammeter can lead to serious problems.

[rotorwrench]

Aircraft use shunts purpose made depending on system load amp rating. Some of the helicopters use a shunt wire but the wire length is calculated to work with the amp rating of the system. Here is an example from aircraft spruce of the purpose built types.
https://www.aircraftspruce.com/catal...clickkey=14951
I recently modified the Robinson helicopters to add a circuit protector to the out take from the shunt to protect the ammeter if there is ever a short in the alternator current line. Sometimes the alternator fails internally and it will kill an ammeter.


Some ammeters are internally shunted but it's hard to tell on an antique meter unless you can take it apart and look inside.

[Ken/Alabama]

The large yellow/black wire on the rear of the power gen is going straight to the ammeter like the stock generator. The power wire for the fan relay is hooked to the batt side of the foot starter. This car is wired stock with the exception of the power gen and the fan.

[flatheadmurre]

Fan and other loads should be on the same side of the ammeter as the generator.
On the other side should be only the battery.

[Ken/Alabama]

Originally Posted by Charlie Stephens

Here is a picture of the shunt I used on my '32 amp meter. If I was doing it again I would run two identical wires from the generator (alternator in your case) to the amp meter. One will be attached to each side of the amp meter. I will use the same gauge wire so the reading is cut in half and in case of a failure the remaining wire will be large enough to carry the load. The amp meter reading is cut in half which is what I wanted.

Charlie Stephens

Thanks Charlie, I like that idea. Is there any particular lenth the shunt wire needs to be?

[Charlie Stephens]

Originally Posted by Ken/Alabama

Thanks Charlie, I like that idea. Is there any particular lenth the shunt wire needs to be?

You are trying to match the internal resistance of the amp meter to the resistance of the shunt. They are both very small numbers. I used trial and error. Just be sure the shunt can carry the full load if the amp meter fails. Running parallel wires from the power source and connecting one to each side of the amp meter would be the quickest solution.

Charlie Stephens