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340 U Alt.

A

Anonymous-0

Well-known Member
When I checked my alt. with an ohmeter I went from big batt. terminal to alt. case and there is continuity. Does that sound like a bad diode in the alt.or something else? Alt. charges OK but batt. runs down when not running.Thanks for your help.
 
A good alternator will show continuity with the ohmmeter probes connected one way, but no continuity when the probes are reversed.

----

If your meter has a DC current setting do this: Set the meter to read DC current, disconnect the wire from the alternator BAT post, then connect one meter probe to the wire end and touch the other probe to the BAT post. A good alternator will draw no current or just a few milliamps of leakage current.

Or simply disconnect the wire at the BAT post when you shut down (tape the wire terminal for safety!). If the battery now stays up the problem is the alternator.
 
Do exactly what Bob M indicates. If your meter has no Amp setings, do this.
use a test light (or a 12 volt small light bulb) and see if it will light if placed with the side against the big terminal of the alt. and the removed big wire on the scnter terminal. if it lights, there is a bad diode in the alternator. JimN
 
I checked with test light did not light it up. I haven't had a chance to unhook bat. wire at the alt. yet. Got a brand new grandaughter. Wife says priority list #1 grandaughter #101 340 Utility.Thanks for the help. And thanks for reminding me about taping hot wire. Al W
 
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