alternator & charging questions
Thread Starter
Instructor
Joined: Jan 2006
Posts: 240
Likes: 0
From: San Antonio TEXAS
alternator & charging questions
My 99 FRC's alternator was making a high pitched whistle so I had it checked out and new bearings installed just cause. Sound is still there and the shop indicates that it sounds like it's dealing with a heavy draw.
I'm showing about 14.5 amps at the alternator at idle and slightly less at the battery. Stays pretty much the same as rpms go up. I also
noticed a 1.5 to 2 amp draw between the battery and the disconnected ground cable with the ign. off. Sounds high to me. Any info appreciated as usual
Interesting in that a stethoscope shows the sound is from the alternator but a plastic tube in the ear shows that it is centered right at the front on the shaft and nut of the pulley.
I'm showing about 14.5 amps at the alternator at idle and slightly less at the battery. Stays pretty much the same as rpms go up. I also
noticed a 1.5 to 2 amp draw between the battery and the disconnected ground cable with the ign. off. Sounds high to me. Any info appreciated as usual
Interesting in that a stethoscope shows the sound is from the alternator but a plastic tube in the ear shows that it is centered right at the front on the shaft and nut of the pulley.
Tech Contributor
Joined: Jan 2007
Posts: 19,471
Likes: 1,171
From: Dyer, IN
My 99 FRC's alternator was making a high pitched whistle so I had it checked out and new bearings installed just cause. Sound is still there and the shop indicates that it sounds like it's dealing with a heavy draw.
I'm showing about 14.5 amps at the alternator at idle and slightly less at the battery. Stays pretty much the same as rpms go up. I also
noticed a 1.5 to 2 amp draw between the battery and the disconnected ground cable with the ign. off. Sounds high to me. Any info appreciated as usual
Interesting in that a stethoscope shows the sound is from the alternator but a plastic tube in the ear shows that it is centered right at the front on the shaft and nut of the pulley.
I'm showing about 14.5 amps at the alternator at idle and slightly less at the battery. Stays pretty much the same as rpms go up. I also
noticed a 1.5 to 2 amp draw between the battery and the disconnected ground cable with the ign. off. Sounds high to me. Any info appreciated as usual
Interesting in that a stethoscope shows the sound is from the alternator but a plastic tube in the ear shows that it is centered right at the front on the shaft and nut of the pulley.
Thread Starter
Instructor
Joined: Jan 2006
Posts: 240
Likes: 0
From: San Antonio TEXAS
Volts, not amps.
Haven't tried it without a belt but will as soon as I get to it tonite.
Also, make that 14.5 VOLTs at the alternator. The amperage draw is correct, actually higher than that initially.
Also, make that 14.5 VOLTs at the alternator. The amperage draw is correct, actually higher than that initially.
Tech Contributor
Joined: Jan 2007
Posts: 19,471
Likes: 1,171
From: Dyer, IN
http://forums.corvetteforum.com/1567522286-post590.html
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 244
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Unless you allow the BCM to enter sleep mode, you will have a draw....higher than milliamps.
http://forums.corvetteforum.com/1567522286-post590.html
http://forums.corvetteforum.com/1567522286-post590.html
Based on Bill's measurements, s/b approx 15-25 ma at "rest", or "sleep" mode. 
Instructor
Joined: Oct 2010
Posts: 240
Likes: 2
From: Yangpyeong Gyeonggi-Do
Sorry, been around allot of solid state electronic devices over the years and have never known them to make noise based on the load applied. I would favor the mechanical reason. As suggested above pull the belt and see what happens. Would not be the first time I was proven wrong though. Let us know what you find as the cause. Interested now...
Safety Car
Joined: Dec 2004
Posts: 3,526
Likes: 20
From: Santa Fe TX
My suggestion would be to have them check the voltage regulator on the alternator. I pulled mine off thinking the bearings were making noise and while they were fine, the shop that tested it said the voltage regulator was bad.
This assumes you have isolated the issue to the alternator and it's not one of the pulleys / tensioners / belts.
I can't remember if the Regulator made a difference in noise on mine, but it made a world of difference in idle quality (before the voltage would drop every so often and you could hear the noisy fuel pump reset when idling at a red light). It does seem like there was a whine that was fixed, but I've slept since then...
This assumes you have isolated the issue to the alternator and it's not one of the pulleys / tensioners / belts.
I can't remember if the Regulator made a difference in noise on mine, but it made a world of difference in idle quality (before the voltage would drop every so often and you could hear the noisy fuel pump reset when idling at a red light). It does seem like there was a whine that was fixed, but I've slept since then...
Racer
Joined: Feb 2003
Posts: 418
Likes: 28
From: Evansville IN
Unless you allow the BCM to enter sleep mode, you will have a draw....higher than milliamps.
http://forums.corvetteforum.com/1567522286-post590.html
http://forums.corvetteforum.com/1567522286-post590.html
To the OP. That's about what my truck was showing when running the other day. Actually it was 11-13 amps charging rate on a good battery but that sounds in line with the norm to me.
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Intermediate
Joined: Mar 2011
Posts: 41
Likes: 1
From: Perth Western Australia
I have a similar whine from my alternator. The unit was removed, stripped down on a bench, reassembled and bench tested..It is charging correctly, and the auto electrician said that these alternators have an air gap tolerance between the armature and housing, and if that tolerance is a little bigger than design, it makes that whining noise. I am only repeating his words, does any one else know of this issue? Other than than that, it charges and runs ok. Also have a whine back through front speakers at idle, cant hear it at normal driving speeds, or with the volume turned up a little.
Chees, Eric
Chees, Eric
Burning Brakes
Joined: Oct 2004
Posts: 931
Likes: 35
From: Rowlett, Texas
I have a rebuilt Bosch on the wife's old Mercedes that has always whined like the devil when the draw increases - turning on the lights will definitely increase the noise. Unplugging the unit will render it insta ntly totally quiet.
It's been that way for 10 years. The local alternator repair shop said it's electrical whine, due probably to a bad diode. He wants $100 to go through it, but I've just put it off, since it works fine.
I also notice that the Vette alternator whines a little bit upon first starting after sitting and discharging for a week or so.
I'm not well-versed on the subject, so I won't comment as to the exact source of this electrical noise, I'll only say I don't think it's a mechanical flaw.
DG
It's been that way for 10 years. The local alternator repair shop said it's electrical whine, due probably to a bad diode. He wants $100 to go through it, but I've just put it off, since it works fine.
I also notice that the Vette alternator whines a little bit upon first starting after sitting and discharging for a week or so.
I'm not well-versed on the subject, so I won't comment as to the exact source of this electrical noise, I'll only say I don't think it's a mechanical flaw.
DG
Le Mans Master
Joined: May 2006
Posts: 7,875
Likes: 254
From: Hillsboro OR
Sorry, been around allot of solid state electronic devices over the years and have never known them to make noise based on the load applied. I would favor the mechanical reason. As suggested above pull the belt and see what happens. Would not be the first time I was proven wrong though. Let us know what you find as the cause. Interested now...
Pro
Joined: Aug 2010
Posts: 545
Likes: 4
From: Calgary Alberta
I'd also support the diode theory. Had a similar problem just recently with my Ford Escape. I'm an electronics technician/master electrician so when the alternator went I felt the need to diagnose the failure. Turned out several diodes were bad. This would lead to a situation where parts of the stator end up carrying more load then they were designed for. Simple to test if you know how to use a multimeter. There is a 3 phase bridge rectifier inside the alternator. You need to check all the diodes for shorts or more likely in your case open. Often they will be physically broken and easy to see.
