Alternator Help

Ok heres the deal, my G/F drives a 95 Dodge Neon. It started making some funny noises coming from the alternator I tested the alternator and found there to be excessive diode ripple. Fine enough, so i go and buy another alternator, which costs huge $ for this stupid car, and then a couple hours of fighting with it, I have it all replaced, newly remanufactured alternator is in, I start it up, all is good for a minute and then here comes the same noise again that the old alt was making. It sounds like it is whistleing, like an electric motor that is struggling. So I go and replace the ground straps with thick welding cable. I thought that there might be a short in the feed wire for the alt. So I took it off and ran a Jumper cable to the alt. directly to the battery Same deal. The noise gets louder and you can kind of hear the alt. struggling when you turn on all the loads. I tested the alternator and battery, and all my connections and they all test good. The alt is definately what is making the noise and I am 100% positive that it is not the belt. Does anyone have any ideas of what else I can check?

did you swap the old pulley to the new alt? if its a "new" noise to the vehicle i dont see why the new alt would make the same noise as the old one... any new electronics inthe car??

mike

Nope the new alt came with a pulley already on it. I just pulled out the new alt and am taking it back hoping that by some odd coincidence that perhpas I recieved a defective remanufactured one. What a bastard it is to change tho.

I´d start pulling fuses and see if you havn´t got some kind of line loss. I´ve had good alternators put out high voltage and heat up the battery because of line loss. A splice that is partially grounding, through moisture, if it´s been loosing juice through moisture for any amount of time, usually oxidizes and turns green. If you have a battery thats not maintenance free, have a look inside and see it it´s boiling (with safety glasses on and cigarette in your mouth).
High voltage or excessive amps, is a sign of an unhealthy electrical system. Windshield motors that fail to return to park position, rear window defrosters that don´t turn off. Even ignition coils, that have an internal short. Often won´t pop a fuse, but use a lot of juice.
If you have a meter that tests for Alternating voltage it´s worth a shot, excessive RF or or any odd frequency (A/C) can load things up.
The only way to be absolutly sure of a battery is a load/Amp test. Though a specific gravity check, often tells a story also.

There is the possibility that the "new" alt has funky diodes too.. if the noise is coming from the alt, it is stator whine caused from the windings actually vibrating from magnetic field collapse...could come from excessive load such as a low charged battery, or the regulator running wild...FYI...most chainstore rebuilds actually have very little "new" in them beyond bearings and brushes..they can sell them with "lifetime" warranties because there is little investment in the rebuilding. There is nothing inherently wrong with used parts, but the testing used by most rebuilders is at times iffy...especially the go/no-go indicator light diode testers...

Ok problem solved! I tested the alt, with several types of testers and it still tested good but sounded like a powersteering pump gone bad, so I finnaly sucked it up and removed it and exchanged it for another reman. and the noise was gone. It just sucks, this Alt. is no picnic to change it took several hours to do, damn defective NAPA remans, I never usually use them but they had one in stock and delivered it in a couple minmutes, but in the end ended up causing few days of work. Thanks for all the advise tho.