Alternator is Whining...Any Advice?

(elleduke) · (elleduke) **Join Date: Aug 2005** 07-06-2006, 11:06 AM

This last weekend we noticed that a high pitched whining noise was coming from the engine, Indmar TBI. I think it is coming from the alternator but its hard to tell. I know that the specs on the alternator are 25amps at idle and 70amps at 2,000RPM. I recently added a stereo system but nothing too crazy. I know that from the factory Mastercraft doensn't add additional batteries for amps and lights etc. so I figured the output would be fine to run my system. MTX MXA6004 (Tower speakers) and MXA6001 (subs). Any input or similar experiences would help.

(acurtis_ttu) · (acurtis_ttu) **Join Date: May 2004** 07-06-2006, 12:33 PM

I know alot of high amp alt's whine quite a bit under heavy loads...mine whilll, but it's only noticeable with the enige cover up

(newty) · (newty) **Join Date: May 2005** 07-06-2006, 1:12 PM

You sure the whine is coming from the alt or could it be coming through the speakers

(elleduke) · (elleduke) **Join Date: Aug 2005** 07-06-2006, 1:25 PM

Ryan, Definitely not the speakers. As it gets louder when I open up the engine cover. With the engine being as loud as it is it is hard to isolate the noise and determine if it is something other than the alternator.

(acurtis_ttu) · (acurtis_ttu) **Join Date: May 2004** 07-06-2006, 1:47 PM

HAs the noise nto alwasy been there? Could it be the sound of air being sucked in?

(chas) · (chas) **Join Date: Feb 2002** 07-06-2006, 1:55 PM

Get a small hose or a wrench and hold it the spot you think the noise is coming from and put your ear to the other end. Should help narrow it down.

(luchog) · (luchog) **Join Date: Jun 2002** 07-06-2006, 4:02 PM

grease the belt?

(bob) · (bob) **Join Date: Feb 2001** 07-06-2006, 11:55 PM

did he say grease the belt.....

(mobv) · (mobv) **Join Date: Jun 2002** 07-07-2006, 1:24 AM

A whine in the alternator can be a sign of a bearing beginning to fail or a problem with the "electronics" rectifier with components failing, stator (outside windings) or rotor (inside windings). In any case it will eventually quit charging. I would pull it off and take it to a repair shop and have it checked and repaired before getting stranded.

(rourker) · (rourker) **Join Date: Jun 2006** 07-07-2006, 7:02 AM

I'm w/ George. Most likely electronics. Belts squeal and you can spot a bad belt or if your bearing is failing. Check your batteries, too. Bad batteries that aren't taking a charge will wear out an alternator fast!

(rodmcinnis) · (rodmcinnis) **Join Date: Sep 2002** 07-07-2006, 10:56 AM

If the noise comes from the alternator then it is either the bearings making noise or the windings making noise due to the current vibrating the coils.

If the noise is from the electrical section (windings) then it will be a function of the amount of current the alternator is cranking out. I would expect the noise to dramatically drop when the batteries were fully charged and the current drops. The noise means that the coils are vibrating which means that they could fail due to metal fatigue or possibly wear off the enamel insulation and short out. Also, I have never heard winding noise that would be noticable above normal engine noise so I doubt that this is the cause.

Bearing noise is much more likely. In some cases a ball bearing can get fairly noisey and still last a long time. On the other hand, if the fan belt is too tight you could be wearing the bearing out and it will fail soon.

If the alternator is on a belt by itself you can isolate the problem by simply slipping the belt off the alternator seeing if the noise goes away. You can run for quite a while (a few hours) without the alternator if you keep the stereo off.

I have observed a lot of boats that have a high pitched whine that comes from the engine's air intake. Something in the air intake whistles.