Ammeter Reading With Powermaster Alternator

[51woodie]

I installed a 6V pos. ground Powermaster alternator on my "46 flathead. I used 8ga. to ground the alt. as per instructions and ran 8ga. from the output terminal to the battery side of the starter solenoid. The car charges nicely and the battery maintains voltage. The issue I have is, that the ammeter shows a discharge when I turn the lights on. I've driven for an hour with the lights on, and when I park the car the battery is fully charged.


The yellow wire on the solenoid goes to the ammeter and then to the circuit breaker unit. Shouldn't the ammeter read in the center with the alternator on line? What am I missing?

[51 MERC-CT]

Being electronically challenged, I would say that when the lights are on they are being powered by the output of the alternator and nothing is being drawn from the battery.

[flatheadmurre]

You have to hook the alternator output to the cable originally attached to the BAT post of the regulator to make it work as it was designed from start.

[40cpe]

you by-passed the ammeter with the alternator charge by taking the output wire straight to the soleniod. Ideally, the output wire should go to the distribution point, which in your case should be the board on the firewall that contains the circuit breaker and the ignition resistor. You want the ammeter between the point that the load is distributed in the car and the battery. That way, the ammeter only shows the net difference in alternator charge and currant usage.

[Jack E/NJ]

If all is charging well with a fully-charged battery, the battery side of the solenoid should be ~7.2v with lights on or off at fast idle. Jack E/NJ

[Jack E/NJ]

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Yep, Flatheadmurre & 40cpe seem to have the answer to the ammeter dilemma. Jack E/NJ

[JSeery]

Originally Posted by 51woodie

The yellow wire on the solenoid goes to the ammeter and then to the circuit breaker unit. Shouldn't the ammeter read in the center with the alternator on line? What am I missing?

Sounds like that part is wired correctly, the ammeter is seeing the current flow to/from the battery, but the alternator output needs to go to the voltage regulator terminal (as already stated) or directly to the circuit breaker panel. It is also possible you have the wire through the ammeter loop the wrong direction. After you correct the alternator output wiring, if you still have the issue, I would disconnect the yellow wire and reverse the direction through the loop. If it is currently in same direction as it was originally, it would have to be reversed when you switched from positive ground to negative ground.

Look at it this way, you are connecting the alternator to the battery side of the starter solenoid, it is just the path it is taking. Alternator to voltage regulator to circuit breaker panel, through the ammeter to the starter solenoid. Or if you skip the voltage regulator, then to the circuit breaker then through ammeter to the solenoid.

[Charlie Stephens]

You can reduce the current going through the ammeter by running two wires from the alternator to the ammeter. Connect one wire to each side of the ammeter that way only half of the current will go through the ammeter and the rest will bypass it. Be sure both wires are the same size and each heavy enough to carry all of the current in case the ammeter fails. I accomplished the same thing on my '32 Ford by running a wire loop across the two terminals so only half of the current would pass through the ammeter. The ammeter will read low but if you "tie a string around your finger" to remind you the reading is low you will be ok. See attached for a photo of my '32.

Charlie Stephens

[51woodie]

After reading the above replies, the solution is to run an 8ga. wire from the alternator output terminal to the B terminal of the voltage regulator (It's just on the firewall for good looks), which in turn a yellow wire runs from the B terminal to the B terminal of the breaker module. Is that correct?

[JSeery]

Sounds good to the terminal on the circuit breaker panel. From there through the loop on the ammeter then to the starter solenoid (which I think you already have sorted out).