ftpiercecracker1 Posted March 17, 2013 Share Posted March 17, 2013 Just tonight I noticed a humming or buzzing sound coming from the alternator, engine off and key out. Unplugging the alt makes the noise go away. I have done some preliminary research and have heard something about an 'exciter' wire, what ever that is. Or something has been left on in the cab, which there isnt. ftpiercecracker Link to comment Share on other sites More sharing options...
jimoshel Posted March 17, 2013 Share Posted March 17, 2013 Isolator diode going bad letting current leak thru to the exciter winding. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 17, 2013 Author Share Posted March 17, 2013 Isolator diode going bad letting current leak thru to the exciter winding. Exactly, just as i thought. . . . now, what the heck is that thing again? Link to comment Share on other sites More sharing options...
Geonovast Posted March 17, 2013 Share Posted March 17, 2013 Not sure exactly what an exciter winding is, but a diode is basically a one way valve for electrical current. If it's shorted, it'll let power flow the wrong way when the alternator isn't turning. Could easily be the source of the humming sound. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 18, 2013 Author Share Posted March 18, 2013 To revive this topic, does this mean my alternator is bus, can it be repaired? I have tested it with my multimeter and its still putting out plenty of juice. Soo :dunno: Link to comment Share on other sites More sharing options...
Geonovast Posted March 19, 2013 Share Posted March 19, 2013 It'll probably still function as usual, but could drain the battery if it's leaking current when the truck's off. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 19, 2013 Author Share Posted March 19, 2013 It'll probably still function as usual, but could drain the battery if it's leaking current when the truck's off. With the truck running the battery reads a steady 14 or so volts, but that darn humming is going to drive me insane. :fs1: Link to comment Share on other sites More sharing options...
Geonovast Posted March 19, 2013 Share Posted March 19, 2013 I would replace it. If it's simply a matter of that diode being shorted, you'll charge fine, but it'll hum and drain the battery when it's off. But if that failed component becomes open, you're screwed. I have no idea if the diode itself can be replaced or not, but to be safe, I would replace the entire unit. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 19, 2013 Author Share Posted March 19, 2013 I would replace it. If it's simply a matter of that diode being shorted, you'll charge fine, but it'll hum and drain the battery when it's off. But if that failed component becomes open, you're screwed. I have no idea if the diode itself can be replaced or not, but to be safe, I would replace the entire unit. I am assuming that when that particular component does become open the alternator will no longer charge at all? Link to comment Share on other sites More sharing options...
Geonovast Posted March 19, 2013 Share Posted March 19, 2013 Yup, there would no longer be a connection between the alt and the battery. Link to comment Share on other sites More sharing options...
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