Whining sound when lights on

[AZDatsun]

I noticed lately when I start my car it seems like it takes a bit for the RPMs to stabilize and is down to around 500 rpm and my voltage gauge fluctuates a lot when i first start it. so I give it some gas to keep it going until it’s more warmed up. During these first few minutes my lights are also dimmer until I get it up to around 800+ rpm. Also when I turn on the headlights I get a noise coming from the alternator that used to not be there. Do you think it’s time for a new alternator?

 

 

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[AZDatsun]

Any ideas? How do I tell if it’s my battery or my alternator or belt?


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[Patcon]

If the belt has any real wear, replace it. That's cheap. Then check the battery voltage with the car running and report back

Check the battery voltage before starting the car and then after.

 

[AZDatsun]

My belt looks fine and is less than a year old

I went out and got timings

 

There are no accessories on other than the parking brake light on the speedo guage, AEM afr gauge, and the stock clock when I start the car. The clock obviously is always on.

 

13.5 just off trickle charger

12.92 7:22am

12.83 7:59am

12.75 8:47am

12.72 9:26am

12.71 10:24am

Started car and stabilized to 800rpm

13.44 10:26am

13.51 10.27am

13.52 10:28am

13.52 10:30am

13.50 10:31am

13.49 10:32am

13.48 10:33am

13.46 10:33am

13.45 10:34 am

Shut car off and leaving off trickle charger for now

13.42 10:35am

13.16 10:54am

 12.95 11:42am

12.89 11:58am

 

I noticed if I give it throttle above 800rpm the voltage does increase but the steady decrease is worrisome I think.

 

 

 

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[Zed Head]

Is it a reman?  How old?  Might just be bad bearings in the alternator.  The voltage numbers look good.  If it's a reman it probably has a lifetime warranty.  Go get another one and hope.

[AZDatsun]

The alternator is a rock auto bought it in March 2017

ACDELCO 3341558 (334-1558@A23)

Looks like it’s only a 24 month warranty darn!

 

I just did a parasitic draw test (I hope correctly) by unhooking the negative battery cable and connecting one volt meter lead to the negative post and the other lead to the negative battery cable and I set my volt meter to dca 10amp and I got a reading of between 0.01 and 0.02 so I think that means there is no drain going on

 

 

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[Patcon]

I agree the voltage numbers look pretty good. Someone else could probably chime in but the voltage going down, might just be the charge leveling out in the battery. Not my specialty. Since the voltages are good and it doesn't appear the alternator is being worked overly hard, then I would suspect the noise is from the alternator, but it does appear to be working properly.

[AZDatsun]

Keeping on monitoring battery levels drop seems to be leveling out. So maybe it is just getting back to 12.66. Looks like I will be purchasing a new alternator.

Shut car off
13.42 10:35am
13.16 10:54am
12.95 11:42am
12.89 11:58am
12.84 12:20pm
12.76 1:38pm
12.75 2:58pm
12.75 4:38pm


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