Alternator wiring

Ford whisperer

Ford whisperer

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I'm running a 12 v neg ground gm 3 wire alternator (60 amp) with internal regulator on my '51 ford f1 with 8ba flathead. I've been searching this forum for identifying what the two plugin wires do and where do they route to. (The bat wire seems self explanatory). I'm going to install a Stewart Warner 60-60 amp meter under the dash due to the factory meter never working in all my 13 years of driving this truck. When a prior owner converted the charging system to the 12v alternator, the stock 6v ammeter was not protected with a volt reducer, and could be why that quit showing charge or discharge. Anyhow, the Stewart Warner gauge will match the Stewart Warner oil & temp gauges I've neatly fabricated into the dash. In advance of wiring the new 12v ammeter, I'm trying to understand the reason for those two smaller wires in the plugin. Might be a somewhat sophomoric question to some, but short of undoing the existing new harness previously fabricated, I'd like to understand the workings of this harness. May wind up replacing those two wires as I get into this under the dash. Thanks in advance.
 
The small #1 terminal is the exciter that should be connected to the ignition switch through an idiot bulb and/or resistor (I just use a 12v 6-12 watt bulb). The small #2 terminal is the voltage sensor and can be pigtailed directly to the big alternator bat terminal or to the other side of the idiot bulb at the ignition switch to avoid a very small voltage-sensor current drain. Jack E/NJ

PS: You can also set it up as a one-wire by eliminating the #1 exciter altogether and connecting the #2 voltage sensor directly to the battery terminal. You may have to rev the motor a bit to get the alternator to self-excite from residual magnetism.
 
Okay. These replies & schematics are helpful. But since these old fords originally had 30 amp ammeters instead of an idiot light, what wires get passed thru the new 60 amp Stewart Warner ammeter? I believe the new ammeter has two terminals marked + & -. (Hasn't arrived yet). How to wire this new gauge? Thank you.
 
The ammeter's negative terminal goes directly to the battery positive terminal. Everything else goes to the ammeter positive terminal --- alternator's heavy battery output wire, lights, etc.

However, because the alternator's potential output current is much higher than a generator, a voltmeter instead of an ammeter is advisable. Running that much current inside the cabin under the dash and back out to the battery is a fire waiting to happen.

Jack E/NJ
 
Ford whisperer said:
Okay. These replies & schematics are helpful. But since these old fords originally had 30 amp ammeters instead of an idiot light, what wires get passed thru the new 60 amp Stewart Warner ammeter? I believe the new ammeter has two terminals marked + & -. (Hasn't arrived yet). How to wire this new gauge? Thank you.
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An ammeter connects between the battery and whatever terminal you are using to connect the remainder of the vehicle wiring. The ammeter is looking at current to/from the battery. The lamp in the diagrams is just a load (in your case). You can connect a resistor to replace the lamp or place the lamp in a location it is not seen. You can also just jumper it across, but the whole circuit works better with the resistance. Did you scroll through all of the diagrams? They show multiple ways to make the connections.
 
Thanks jack. That's the info I needed to wire up the new gauge. I'm going to pull the original gauge cluster and examine how ford wired this truck ammeter in the first place. I'll likely unzip the harness from that gauge all the way back to the alternator to closely examine those wires and rewire with new correct gauge wires. So I've been driving this old truck now for more than 13 years with a 3 wire 60 amp alternator connected to the original 30 amp ammeter. It continues to charge at optimum volts and no electrical gremlins causing problems. I wonder if the prior owner somehow bypassed that ammeter when they changed from 6v positive ground generator to 12v neg ground alternator, and that's why the ammeter never worked under my ownership? This is getting real interesting. Thank you for all the great help.
 
The stock amp gauge should work on 12 volts. It does NOT need a volt drop. The wire will pass through a loop on the back of the amp gauge. My guess is the prior owner did not run the alternator wire through the loop on the gauge.
 
Original Ford wiring. The current path is battery to the starter solenoid. From the battery side of the solenoid to the ammeter and then to the circuit breaker panel terminal. The generator output (via the voltage regulator) also connects to the circuit breaker panel terminal. The ammeter is measuring the current flow to/from the battery.

As Jack stated, a voltmeter would be a good idea. The voltmeter does not have to be between the battery and the vehicle loads. Do you have the original F1 wiring diagram? Might also want to take a look at the Ford wiring diagram for a year that used a voltmeter.
 
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Okay. I appreciate all advice. I had no idea that an ammeter in my situation could be such a hazard. The original 6v generator factory setup to the instrument cluster ammeter was of course correct. A three wire 12v alternator wired to an ammeter is likely incorrect for this application. I'm definitely leaning toward installing a 12v voltmeter instead of an ammeter. I'll report progress in a week or so. Thanks again.
 
PHP:
Thanks for that. Very genius-like. However, I'm hoping to avoid spending hours upside down under the dash wangling the gauge cluster out and in, while trying not to disturb all the functioning wiring. So much easier to hang a meter under the dash, don't ya Think? Getting too old and muscles too stiff for under-the-dash work.
 

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Have same exact set up on my '47. I use my alternator as a 3-wire set up so the ALT starts charging immediately.

As TJ said your stock dash amp meter would work with either 6 or 12 volt system - nothing needed. So it sounds like your stock amp meter is non-malfunctional, which is rare given their simplicity. I have aftermarket amp AND volt meters.

A volt meter is more important as its a better indicator of your system's performance. If voltage goes above about 14.5 or especially 15v, it can easily damage any electronics in your system. I had a faulty alternator, putting out excessive voltage, blow out two expensive Pentronic's distributor modules.
 
When I suggested a voltmeter over an ammeter it was assuming a terminal type ammeter. With a loop type of ammeter this would not be an issue. Voltmeters do have their advantages though, as pointed out above.
 
Ok, folks, I am putting a 12v alt on my 41 flatty, it is running electric fans and vintage air, didn't the original generator feed to the voltage regulator and then through the gauge to the starter solenoid. I have the yellow power wire sticking out of the wire loom where thregulator was mounted, can i feed that with the battery wire from the alt.
 
Yes. Didn't you start another thread on this same question? Guess that is ok, but it gets a little confusing. Doesn't mater if it is an alternator or a generator, it is a power source and wires up the same. The exception to that is if the alternator is not a one-wire and requires a separate exciter wire.
 
Yes, I did start another thread, sorry about that it has been a while since I was on this site. thank you for both of your responses. Would you use a three wire or perhaps an alternator from summit that says it charges at a low rpm.
 
I really don't have experience with the more modern one-wire alternators. In the past the 3-wire was the way to go. But I have read that some of the newer one-wires work fine, but I have no personal experience. My alternator is a original generator look-a-like that is not GM. Maybe someone will weigh in with one-wire experience.
 
I'd get the 3-wire. It can easily be converted to a 1-wire, by pigtailing the #2 sensor lug directly to the output and leaving the #1 exciter lug disconnected. You might have to blip the motor to get it to charge without the exciter connected. Or you can do it right, by connecting the exciter lug to the ignition switch and the sensor lug to some remote location. Jack E/NJ
 
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