ammeter wires
- Thread starter Kube
- Start date
Canton_Model_A's
Senior Member
50/50 shot, I say if looking at the back of the ammeter, the right hand side.
Herb Concord Ca
Well-known member
Easiest way is hook up wires and with engine off, turn on headlights, ammeter should show a discharge, if it doesn't reverse the wires.
Marshall V. Daut
Well-known member
Black wire? One wire to the ammeter should be yellow and the other one yellow with a black tracer. Is this a put-together wiring harness? Or are you asking about the (probable) black wire running from the instrument panel light? That can go to either side of the ammeter for power, as I recall.
Marshall
Marshall
I got the harness from Bratton's and it matches the Ford OEM schematic.
Jeff/Illinois
Well-known member
Hey Kube.... hang on tight you guys are sure getting some bad storms up there!
Take care bud
Jeff
Take care bud
Jeff
If the car is wired as a stock 6 volt, positive ground:
Yellow / black tracer to the "Charge" side. (as written on the front of the ammeter)
Yellow to the "Discharge" side.
I suggest you make certain that your black wire to the - negative side of the coil is sourced from the yellow / black tracer from the generator / alternator side of the terminal box as per the November, 1929 service bulletin suggests.
Yellow / black tracer to the "Charge" side. (as written on the front of the ammeter)
Yellow to the "Discharge" side.
I suggest you make certain that your black wire to the - negative side of the coil is sourced from the yellow / black tracer from the generator / alternator side of the terminal box as per the November, 1929 service bulletin suggests.
nkaminar
Well-known member
All thing electrical for the Model A shown here: https://www.mafca.com/downloads/Seminars/2018 Reno Electrical System Alex Janke.pdf
P.S.
Well-known member
Great advice. Thank you. That's how I had it and now can rest calmly
Do to differences in repro ammeters: You still need to test, as Herb said, to be sure.
rotorwrench
Well-known member
Don't forget the wire to the dash light. It's black or armored on later model As and can connect to the battery wire or the generator wire. Some folks rewire the dash to do away with the Electro-Lock pop out switch. The ignition on a stock model A has the electro-Lock to control the ground circuit to the distributor but some modify it to control the power to the coil instead. This stuff sort of throws the original dash diagram in the dust bin.
There has always been confusion about the amp meter connection due to mistakes in diagrams or lack of good descriptions of the two ammeter terminals. The correct way to describe them is one is a discharge terminal and the other is a charge terminal. When a person turns the ammeter face around to look at the back side then the terminals turn around too. The diagrams don't always tell you if your looking at the face or the terminal side. The charge side is connected to the battery terminal in the terminal box on a positive ground model A application. The discharge side is connected to the generator terminal in the terminal box. It's all about current flow either from the battery with engine stopped or from the generator when the engine is running.
Ford rewired the early coil diagram in 1929 so that the coil would register a discharge when the points were closed. When the starter is operated, the ammeter will indicate the points opening and closing by the discharge wiggle of the indicator needle. The only other black wire on the OEM diagram was the power wire to the coil from the terminal box. The red wire on the coil is the breaker wire to the distributor through the electro-lock switch.
Another FYI is the MAFCA electrical PDF. It has some mistakes in this situation. They will show the ammeter with an arrow to the discharge side but it is actually the charge side and the wires are backwards. This would be OK on a negative ground system but not so much on a positive ground system.
There has always been confusion about the amp meter connection due to mistakes in diagrams or lack of good descriptions of the two ammeter terminals. The correct way to describe them is one is a discharge terminal and the other is a charge terminal. When a person turns the ammeter face around to look at the back side then the terminals turn around too. The diagrams don't always tell you if your looking at the face or the terminal side. The charge side is connected to the battery terminal in the terminal box on a positive ground model A application. The discharge side is connected to the generator terminal in the terminal box. It's all about current flow either from the battery with engine stopped or from the generator when the engine is running.
Ford rewired the early coil diagram in 1929 so that the coil would register a discharge when the points were closed. When the starter is operated, the ammeter will indicate the points opening and closing by the discharge wiggle of the indicator needle. The only other black wire on the OEM diagram was the power wire to the coil from the terminal box. The red wire on the coil is the breaker wire to the distributor through the electro-lock switch.
Another FYI is the MAFCA electrical PDF. It has some mistakes in this situation. They will show the ammeter with an arrow to the discharge side but it is actually the charge side and the wires are backwards. This would be OK on a negative ground system but not so much on a positive ground system.
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