Bad alternator, makes whining noise? - F150online Forums


Bad alternator, makes whining noise?

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  #1  
Old 07-17-2004, 06:43 PM
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Bad alternator, makes whining noise?

I have this whining noise coming from the front of my truck. Im thinking its the alternator since its in that general vicinity. If i give it gas you can hear it in the truck aswell as outside. It sounds just like a psd turbo winding up if go wot. It gets really annoying when your trying to listen to music and it drowns it out while cruising.

Is there any way I can check to see if it's not working properly? When I give it gas to about 4000rpms while in park the lights dim a bit. Is this a tell tale sign that its going?
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Old 07-17-2004, 06:52 PM
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Does the belt seem to be in good condition? What you describe sounds like it's slipping. If so, then you are on the right track with the alternator.

Hunt4Fun
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Old 07-17-2004, 06:58 PM
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Its not the belt. Or it could be. But im going to replace that soon if i do the alternator.
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Old 07-17-2004, 11:09 PM
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could be a pulley (idler) causing the noise. could be the belt slipping.

could be the aftermarket pulley if you've done a modification.

If you have a gatorback belt on, it could also cause the noise.
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Old 07-18-2004, 01:27 AM
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No aftermarket pullies and I do have a gatorback.
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Old 07-18-2004, 02:04 AM
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I dont think its the belt as it didn't make the noise when it was first put on. Didn't really start till went offroading a lil. I hear it no matter what rpm im at.
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Old 07-18-2004, 05:07 PM
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Old 07-18-2004, 05:30 PM
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I've emailed that guy more then 10 times to jusk ask a few question's about that alternator. No answers back at all. So i'de be a bit leary about buying it.
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Old 07-19-2004, 12:37 PM
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If you aren't sure it's the alternator/belt maybe you should check the AC clutch.......does the noise change with your hvac off/on. Just a thought Phil.
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Old 07-21-2004, 12:07 AM
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one way i know if it was the alternator if you can move the pulley up and down cause the only thing in the alternator that could make a noise like that is if the bearing on the shaft through it is out but i would see if i could move the pulley if it moves a lil than you know it is the bearing


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Old 07-30-2004, 10:28 AM
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mine did that too!

ok. if you still need to know if it's the alternator just take off the belt and spin the alternator pulley. if it starts making that noise again (not as loud of course) it's the bearings going out of it. you can trade in the old one for a rebuilt one for about $150. hope this helps.
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Old 07-30-2004, 08:18 PM
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It would've been nice to get some emails saying I got responses. I bought a alternator from a mustang owner. Almost brand new 150amp alt.

Its not the a/c cause it does it when its off too.
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Old 04-20-2012, 03:34 PM
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Same problem

97f150f/s when you figure it out.let me know,,im having the exact same issue..cant do anything about it now cause im offshore,,but im taking it in when i get back...jblanchard29@yahoo.com..send the answer to that email thank you
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Old 04-20-2012, 04:12 PM
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Quote:
Originally Posted by SEACHASER1(FX4) View Post
97f150f/s when you figure it out.let me know,,im having the exact same issue..cant do anything about it now cause im offshore,,but im taking it in when i get back...jblanchard29@yahoo.com..send the answer to that email thank you
This thread is about 8 years old, - -it's a good bet he figured it out.

For the 97/98, -Could be the MEGA Fuse 175amp or the inline mini fuse 15amp. The alts will have a high pitched whine when either fuse goes. BUT, you will get battery light illumination in either case.

Easiest way to check is to fire it up and poke a meter around. If everything is fine there. Remove the belt and fire it up. If you don't hear it, - it's a pulley, - most likely the idler. Could be the tensioner or the alts pulley as well.

NOTE: When you change the belt, - it's recommended to change the complete tensioner at the same time. Personally, I change both tensioner and idler pulley when servicing the belt in these vehicles. Although the idler pulley isn't recommended, - they fail just as much.
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Old 04-21-2012, 01:44 PM
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Tensioner pulley
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