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Please call me Mike
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I want to check the Diodes in my alternator. You can do this by setting the multi-meter to AC and looking at the voltage. I was wanting to know what the upper acceptable limit is.

I haven't been able to find an exact number other than zero. All 3 of my cars have some voltage, all are less than 1/2 volt.

thanks
 

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Your answer means you have to understand the electrical function of a diode. In a circuit a diode is essentially a one-way bridge. The amount of voltage you see will vary with RPM but if it's there the diode is working.
 

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A diode is an electrical check valve. This assumes you know what a check valve is.
An alternator is a poly phase generator. The World operates on 3-phase power. Automotive alternators have more than 3-phases, i.e. poly phase. The diodes convert the AC to DC with a lot of ripple. The battery smooths out the ripple. Never run the engine without a battery. Electronics don't like AC ripple.

3G has 4 diodes.

 
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