Model A ammeter

[Conaway2]

Did original ammeters measure -20 to + 20 amps ? I’ve seen some that have a 30 amp range. Also, did original ammeters have the Ford script on them ?

Thanks - Jim

[johnbuckley]

The picture in the service manual for Jan 1928 shows 20 discharge to 20 charge and no Ford script

[johnbuckley]

here's the pic .

[alexiskai]

My understanding is that the generators, as originally set up, should not put out more than 20 amps – if you were getting more than 20 amps you were doing it wrong. So ± 20 amps was the original setup for the ammeter.

[Patrick L.]

The meters were 20 amp. Can't tell you about the logo. These generators shouldn't really be set to put out more than about 12 amps. Many of the junk repro units are 30 amp.

[Conaway2]

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Thanks all. I’ve come across a very old ammeter - old enough to be original, but it has the -30 to + 30 scale on it, so I’ll assume it’s after-market unit.

[alexiskai]

Ammeters in later cars (before 1940) read up to 30 or 40, maybe it's designed for one of those, or for another marque.

[Charlie Stephens]

Originally Posted by Conaway2

Did original ammeters measure -20 to + 20 amps ? I’ve seen some that have a 30 amp range. Also, did original ammeters have the Ford script on them ?

Thanks - Jim

How about a picture?

Charlie Stephens

[Badpuppy]

The ammeter in the Model A measures battery charge, not generator output.

More than 20A charge means your battery is probably bad and your generator will soon expire, >20A discharge means the stock battery will be depleted very quickly, possible short somewhere.

[BRENT in 10-uh-C]

Originally Posted by Charlie Stephens

How about a picture?

Charlie Stephens

Like this one??


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[Ray in La Mesa]

Model T ammeters had Ford script, A's did not.

[redmodelt]

The meters in any T or A I have worked on measure the generator output or draw not the battery voltage. If you did see the needle on the negative side with the engine not running, that would mean an draw somewhere such as short, lights on or cutout stuck. To read battery voltage you would need a volt meter hooked up different.

[BRENT in 10-uh-C]

Originally Posted by Badpuppy

The ammeter in the Model A measures battery charge, not generator output.

Originally Posted by redmodelt

The meters in any T or A I have worked on measure the generator output or draw not the battery voltage. If you did see the needle on the negative side with the engine not running, that would mean an draw somewhere such as short, lights on or cutout stuck. To read battery voltage you would need a volt meter hooked up different.

Mark, I almost responded to this too but what I think his point is the needle is registering how much amperage the battery is (-or isn't) receiving. I think his point is that if the generator is set to charge the battery at 10 amps however the lights are drawing 8 amps, the ammeter is only going to show a rate of 2 amps going to the battery. Conversely, even if the generator is charging 10 amps however the lights are using 12 amps, the ammeter needle will show 2 amps discharge.

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