Sorry to keep bugging everyone about this, but I just don't know.77 dodge van 318. On startup ammeter needle swings from fullcharge to midrange. Loud squealing when ammeter needle swings to fullcharge. Noise goes away after engine warms up. I think I triedtightening the belt long time ago and made no difference. Visualinspection of belt appears ok. It is one of those kind that is serratedon the pulley side, but no glazing or obvious wear. Looking at a shop diagnostic report sheet from long ago it is somewhatillegible but says, under "Alternator Output: Bad Dode stator" which Iguess legibly written means: Bad Diode Stator? Would this cause thenoise? The belt looks ok and I brought the alternator down to Autozonefor them to test on their machine. Test said it was ok, but Mgr.there said it was probably a bad diode in the alternator.Should I buy a new alternator and see if the noise disappears?

==============Informative diagnostic post....good for you.....Addressing your LAST question in the post........NO!!!!!!!!!!!!!!!!not yet.The needle should raise on ANY vehicle, momentarilyafter startup as the generator recharges the battery.(fact, not fiction)I would not condem the altenator yet, as long as thecharging system seems to be doing it's primary job,and your main symptom is the noise.Keep your money in your pocket for now.now ..as to the topic, and your main concerns... being a tech....i would'nt suspect the statormaking the noise, but that doesn't eliminatethe FACT that it still could be the altenatormaking the noise, or the stator for that matter.Quite frankly....i don't know.I defer to higher minds, which will be with youshortly if you're patient.On closing..... You should be informed that I AM NOT.....a fan of AutoZonedOut parts.....especiallyelectrical anything!!with that said.......:)still..... jest to see........ you could ALWAYS....carry it back ifthe...

The way regular belts grip the pulleys is on the sides of the the sides of the belt (pulleys too) with sand paper and seeif that makes any difference.cuhulin

Bad Diode Stator means?

Aug 04, 2007 21 Replies

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cuhulin 18 years ago

The way regular belts grip the pulleys is on the sides of the belts.Scuff the sides of the belt (pulleys too) with sand paper and see if that makes any difference. cuhulin

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Mike Romain 18 years ago

That 'only' works as a diagnostic tool to ID the noise.

The test is easy. Can you make the alternator pulley slip by hand. If so the belt is done in.

Face it, you need a new belt.

Worst case you can get a harmonic balancer puller and remove the crank pulley to get the new one in because that noise is going to really hurt your sale price.

Mike

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