Alternator Noise/Question
Thread Starter
Burning Brakes
Joined: Nov 2000
Posts: 948
Likes: 0
From: Johnston Iowa
Alternator Noise/Question
I have a PowerMaster alternator in my car that has not been used for a couple of years now. I just got the car going again and I noticed it is making a whining noise when the car is running? The noise is like an electrical whine that goes up and down as you rev the motor. I checked it and its putting out 14.4 volts and I also made sure my battery is good and charged. I went ahead and took it to Napa and had them spin it up and it tests good and did not whine at all. Any ideas of what might be causing it to whine when its in the car and the car is running? Thanks.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
If it is putting out a constant 14.4 volts...and not dropping to about 13.5 volts when the battery gets fully charged...your voltage regulator is not functioning properly. If you don't have a separate regulator box, then the regulator is built into the alternator and your alternator would need to be rebuilt with another regulator module or by exchanging the alternator assembly.
P.S. You might try removing the electrical connector on the alternator and cleaning the connector contacts and the pins in the alternator, then trying it again. That connector has a 'feedback' circuit which uses the battery voltage to set the regulator voltage. If the contacts are corroded/dirty and the 'feedback' signal is not getting to the alternator, the same problem can occur.
P.S. You might try removing the electrical connector on the alternator and cleaning the connector contacts and the pins in the alternator, then trying it again. That connector has a 'feedback' circuit which uses the battery voltage to set the regulator voltage. If the contacts are corroded/dirty and the 'feedback' signal is not getting to the alternator, the same problem can occur.
Last edited by 7T1vette; Jul 30, 2010 at 11:25 AM.
Thread Starter
Burning Brakes
Joined: Nov 2000
Posts: 948
Likes: 0
From: Johnston Iowa
So I have it wired where I shoot the main power wire out of the alternator to a junction point. Off that point I have my 2 spal fans and electric fuel pump wired. One Spal fan is toggled and the other is connected to a sending unit to turn the fan off/on. I checked the voltage at the alternator and the junction point and they both read the same voltage. I did not check it for period of time to see if it was going up or down. The alternator tested good at Napa and did not whine on their machine which makes me wonder why it does in the car??? On yeah and it's an internally regulated alternator.
Thread Starter
Burning Brakes
Joined: Nov 2000
Posts: 948
Likes: 0
From: Johnston Iowa
Tonight I thought I might try disconnecting the heavy output wire off the back of the alternator and see what it sounds like. I ran this same setup for a number of years with no issue but I do have a Optima Yellow Top deep cycle battery that is starting to get kind of old. The battery still takes a solid charge and seems to be working fine. Could the battery be puttin a hurtin on my alternator?
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
Tonight I thought I might try disconnecting the heavy output wire off the back of the alternator and see what it sounds like. I ran this same setup for a number of years with no issue but I do have a Optima Yellow Top deep cycle battery that is starting to get kind of old. The battery still takes a solid charge and seems to be working fine. Could the battery be puttin a hurtin on my alternator?
Thread Starter
Burning Brakes
Joined: Nov 2000
Posts: 948
Likes: 0
From: Johnston Iowa
Reason I went with the yellow top deep cycle was to allow for my single fan to continue run after shutting the car off to continue to keep air moving across the motor and vent all of the heat out from under the hood. Once things cooled down the sending unit then automatically turns that fan off. The yellow top handled the power consumption of the single Spal fan with no problems at all and I always had plenty of battery to crank it back up. I ran this battery and setup for a number of years with no issues at all. I hope to get back out in the garage and take a look at it again tomorrow.
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Safety Car
Joined: Jun 2004
Posts: 4,364
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From: Beecher Illinois
I had a whine under the hood of my black79, thought it was the AIR pump going out.
Turned out to be the alternator FAN.
I had found a correct no./date alternator. Didn't like the condition of the fan so ordered what should have been a 'correct' fan. It wasn't. Was 10 blade 5 1/2" diameter. Figured I'd go with it.
Then I came across a correct NOS 11 blade 5 1/4" dia and swapped it out.
No more whine. Noticed the fan blade angle was quite different between the two.
Turned out to be the alternator FAN.
I had found a correct no./date alternator. Didn't like the condition of the fan so ordered what should have been a 'correct' fan. It wasn't. Was 10 blade 5 1/2" diameter. Figured I'd go with it.
Then I came across a correct NOS 11 blade 5 1/4" dia and swapped it out.
No more whine. Noticed the fan blade angle was quite different between the two.
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