Technical Generator / Alternator Question

I have another question. If I swap the Generator to an Alternator would should I do with the charge indicator?
I only know Alternator cars that have a voltmeter. Will the charge indicator still work? or could the charge indicator heat up and start a fire?
Thanks again Herbert

 

Don't use a one-wire alternator, use a three wire instead. They work better anyway, and will allow you to retain the indicator light and have it function correctly.

 

If you have a factory ammeter in the car, make sure your new alternator output doesn't exceed it's ampacity. Pushing too much amperage through it can cause the magic smoke.

 

Hi Doublepumper I do not have a light

 

I'd suggest converting your ammeter to a voltmeter. Take one out of its normal housing, trim to fit in place of the ammeter.

 

You will want to wire your amp meter shunted so full current won’t be running through it.

 

The problem with shunting one is accuracy is out the window... and an ammeter is a poor choice for monitoring alternators anyway.

 

I agree a voltmeter would be a better choice, I was just passing the shunted idea on in case he wanted to use the original meter. You have forgotten more on wiring than I know.

 

First off , it isn't the amps that an alternator or generator is rated at that screws up an ammeter, it is the load that the system demands that flows though the ammeter that will burn it up. Simply meaning, if you have a simple electric system without a bunch of items that draw extra with combined components drawing more amps together than the ammeter will handle you can overload and burn the ammeter up.

On the other hand a simple car with maybe a rather simple AM-FM radio head unit with no amp and a simple heater and no electric windows or electric seats or other accessories that draw a bunch of power you are safe with an alternator and the ammeter. Still I would prefer a volt meter.

Poking around looking for wiring diagrams for alternator swaps I found this one. You do need your decoder ring on as it shows both volt meter wiring and ammeter wiring.

 

A powermaster has the ability to use your I-did-it light and the stock wiring. I connected it that way on my car. The light works perfect and if I want to see the voltage I have meter that plugs into the cigar lighter.

 

Thanks, I was thinking the same

 

Thanks for all the info

 

The ammeter will work just fine with your 12 volt alternator. They depend on the amperage flowing through them, not the voltage. My cars have their original meters and no problems at all.

 

I disagree with the schematic shouldn't the ammeter be between all loads and the battery so it will see the charge or discharge to the battery the way it is shown only output if the alternator will register.

 

I have seen more cars and garages burn to death (yes the cars were parked and shut off) to last me a life time. Some were rare too. Like the white and gold Hurst Chrysler my buddy had. Switch to a volt gauge.

 

FWIW, 59, I did it this way.

ONE wire, off the shelf rebuilt GM alternator. 8GA charge wire. I like BIGGER wire! I connected the charge wire to the downstream post on the amp meter/gauge ,effectively bypassing the gauge. This way everything that received power, originally, still does so. After market Volt meter.
Been this way since 2009. Over 20,000 miles.

Ben

 

Arguments both ways the induction ammeters will reduce the fire chances it does not cause extra resistance. Volt meters can give false information there is a bad high resistance connection between the gauge and the battery

 

If you have the gas pedal start on your Buick, you will have to change that out if you go to an alternator. I forget what year Buick stopped using the gas pedal start. Anyway, I know that the starter relay uses the generator armature and brushes as a ground. That way the starter will crank until the generator starts putting out current and it prevents the starter from operating after the engine starts.

 

Maybe, maybe not. If you used the idiot light circuit available on the three-wire alternator, you'd have essentially the same thing. You might need to use an additional relay to control the start relay to reduce relay coil load. You'd need to match the relay coil load to the same current draw as the light to prevent damage to the regulator. A relay with a 20 mA coil draw would do the trick.

 

I won't disagree with any of this, but it doesn't take into account current spikes that can show up under a hard start/low battery scenario. These generally don't last long, but it can be a crapshoot as to how well the gauge withstands them. The type of gauge matters too; an inductive type with no physical wire connection (the wire goes through a metal loop, not to two terminals) is best as the worst-case is you kill the gauge but otherwise there's no meaningful smoke let out. It's the type with wire terminals that cause the problems...

 

The only inductive ammeter I’ve seen were in the old Fords, but just a 30 amp I think. Did anyone make a 60-etc?

 

Ford used those at least into the early '60s and did actually use them with alternators on the '63-64 full-size Mercurys. But I don't know how big those alternators were, so I can't say what their 'rating' is. They're not all that accurate...

I believe Ford made a wholesale switch to shunt-type ammeters (when used) in '65, which have their own issues.

 

Find an aftermarket voltmeter that has 12 volts at the top center of the dial. Take the case apart and figure out how to mount it behind the stock glass of the ammeter. After hooking it up, any time the needle is toward the charge side it is more than 12 volts, so it's charging. If the needle goes to the left of center or toward the D side something is wrong if the engine is running.

 

I will buy a Voltmeter, I was hoping their is a other SAFE way. The cluster on a 59 Buick is not easy to remove

 

I'm in the same boat - converted the 41 Chevy to 12V/alternator, and was asking myself the same question regarding the ammeter.

I'm pretty new to that concept of a "shunt" - actually had to look it up (as a German anyway) - but not sure if I understand it right - I found this on a Ford forum:



So a shunt is basically just a kind of "bypass wire" that takes most of the load from my ammeter - and I guess the difference of the cable diameter/gauge is in some sort of relation how much load is taken over. Does that make any sense?
If I use a 10 gauge wire from my alternator to the starter, I should be good?

P.S. the car has basically just lights/ignition and a radio - so nothing fancy or power hungry.

Thanks, Frank

 

The sixties big Pontiacs had the best amp meter. It worked like a amp probe. It said, "Battery".

 

Well... A current shunt is basically just a resistor, usually with a very small resistance. When current goes through something with a resistance you get a voltage drop proportional to the current, according to ohms law:
Volts=ohms*amps
If the resistance was 1 ohm and the measured voltage drop was 1V, the current has to be 1A. Now, 1V loss is far too big to be acceptable, but something more like 1 milliohm could be used, that would give you 1mV for every amp, and a relatively low voltage loss even at hundreds of amps. If great accuracy isn't necessary you can simply measure the voltage drop over a suitable length of wire, instead of using a dedicated ballast resistor.

There may be other ways to use shunts with old automotive amp gauges, you never know what someone may have dreamed up through the years, but this is the common way to use a shunt to measure current - run the current through a small resistance and measure the voltage across it, then do the math to figure out what the voltage says.