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How to test for defective diodes

PostPosted: Sun Mar 16, 2014 8:15 am
by Hippo
I have one of your 4023 alternator. Recently, the alternator emitted a strong "burnt plastic" smell that's characteristic of a burnt diode. However, the alternator is still working. I wonder if only one diode may have gone bad while the others remain OK. Is there a simple test that I could do to confirm this?

Re: How to test for defective diodes

PostPosted: Sun Mar 16, 2014 11:56 am
by Coulomb
A diode failure will reduce full output by about 1/3. You can do a full field test with a low battery to check full output.

Re: How to test for defective diodes

PostPosted: Tue Mar 18, 2014 6:07 am
by Hippo
Thank you for your reply. Is there a danger/problem (for the batteries or...) using the alternator with a bad diode? Can a bad diode be replaced by itself or must all 3 be replaced at the same time? Where would I find the RPM vs. Amps chart for the 4023?

Re: How to test for defective diodes

PostPosted: Wed Mar 19, 2014 12:03 pm
by Coulomb
Diode failures are usually associated with a high voltage transient, such as those which occur with battery selector switches. If one diode has failed, it would be prudent to change all diodes.

With an inoperative diode the battery is subjected to increase ripple and will warm up more during a charge and not charge as efficiently.

Find the RPM versus output chart here: http://www.amplepower.com/products/alternators/index.html