Alternator/Charging 200: New Developments II

Mike Arman Armanmik at
Thu Dec 13 07:39:58 PST 2007

> a) does anyone know how to test a diode? I'm assuming its a resistance
> measure?

Unsolder one end of the diode (take it out of circuit).

Use an ohmmeter, measure resistance one way, then reverse leads, measure 

Only acceptable result, zero one direction, infinity the other.

Zero-zero is shorted, infinity-infinity is open. Sounds like yours may 
be open.

> b) does anyone know what type of diode I'd be looking for if I wanted to
> replace it?

Radio Shack - anything rated at 50 volts PIV (peak inverse voltage) or 
more, plus probably 10 amps or more. These are cheap, come in a two or 
three pack for a couple of bucks. I'd go for 200 PIV, 10 amps. Check 
polarity!!!! White band is cathode end, match the orientation of the 
existing diode.

Symbol for a diode is --->|---, power flows the direction of the arrow, 
but not backwards.

Best Regards,

Mike Arman

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