Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
New alternator installed has a whining noise. Sounds to me like there is a draw already on the alternator. There are three wires going to the alternator. One red going to the back of the alternator and a red and brown going to the side of the alternator in a black connector. If I unplug this black connector amp draw/whining goes away. What could be causing this whining sound? It basically sounds as if there is a draw on the alternator already.
tims auto repair :
Hi, is the battery good?
Yes tested good
Ok, are you getting the alternators in the same place?
Yes, they are brand new units not rebuilds. Replaced alternator 3 times
See I am an auto mechanic in engine repairs not electrical, so feels funny asking questions but this has me puzzled
Ok..you need to load test the battery with the car not running. Then load test the charging system with the engine running
Did a load test on battery with a hand held load tester and checks out good
Does the battery run down after it sits?
Battery holds about a 12.62 charge
No just sitting, not started
I mean when you put a load on the battery with the load tester, most testers will put a 100amp load on the battery
If I use the load tester that goes right to battery terminals it pulls down to about 11.2 -11.4 and it is a 50amp load tester
Ok, does it start well?
Yes, strong starter. Sounds healthy. Powerful start
See it is not like a bad bearing sound. It is a whining electrical sound
How about when you load it for 2 seconds with it running?
Honestly did not try that
Can you try that?
The alternator sounds as if AC, rear defroster, wipers, headlights and all accessories are on
I can. If you give me about 3 minutes I can try that and let you know
Ok, don't hold a load too long
Ok here are the results
13.8 in drive and I even did in gear and that is 12.6
No accessories on either, except hood light
It seems to be operating correctly. How many volts running with no load?
Yes it seems to be doing everything right except the whining sound is horrible
How many volts with no load?
Around 14.4 - 14.6
Maybe even 14.8
Ok, when you unplug the regulator plug the whine completely stops?
Ok...I think this may be a bad batch of alternators. Sounds as if the front bearings are bad. There would be no reason for this
The brown wire from regulator goes to fan fuse relay and the red goes down around to starter
Even under a load
It is no bad bearing
The red is supposed to go to the switch
I did a test with an ear probe and there is no noise; barely with the regulator wire unplugged. Just only while plugged in like it is under a load
The brown to the charge light
I don't have a light gauge
Camaro rs 305 engine tbi
Red goes to what switch? According to wiring diagram it goes to starter. Here is the diagram
Let me switch to a different format, I will send you a diagram
I have a diagram
The bearing has no pressure on it when it is unplugged and not charging
So how can it be a bearing
Well, under load the electromagnets pull on the ohmeter putting pressure on the bearing
It is an electrical whine, not a bearing noise
After you start the car, even if nothing is on, the alternator will be under a load until the battery is fully charged from starting
Yes, but the noise is there always even after driving vehicle for 2 hours. See it never did this before, just started recently and I only heard the noise if say defroster headlights and rear defroster and wipers are on
Charging System Wiring Circuit (VIN E)
But now I hear it with everything off
Let us try an alternator from a different place
Well I recently paid 120.00 for this one and they are brand new, not rebuilt ones and all three from three different stores, but same store name
I think its a bearing