Alternator Replacement?

[Vikas]

I am hearing a faint whining noise at idle and noise increases with load on the alternator. I do not think I had heard that before. On the other hand, I don't think anybody else would hear it either. The 99 Honda Odyssey has 191K miles on. Looking at ebay, used alternators are being sold which come out of donor vehicle with as high as 240K miles! I can also get the brushes on ebay for $10. I was looking for youtube to see if there is any video posted of alternator replacement on Odyssey but no luck. I put the voltmeter on it and it maintains at least 13.6V with full load at warm idle of 750 rpm. So objectively, there is nothing wrong with it yet. Having had to replace alternator on my Maxima at around 150K miles, I am somewhat familiar with end of life alternator and this one is not exhibiting those symptoms yet.

A good OEM quality Densor remanufactured is quite expensive. I am thinking of just buying cheapest from the junkyard with lowest miles and then put the new brushes in it and wait for mine to die. If you guys know any good ones at reasonable price, let me know. I do NOT think putting cheap one from parts store is the way to go especially if mine is still running.

Replacement looks straightforward although there is not much room to get the hand behind it to unhook electrical connectors. I have also head the bracket breaking off on this van. There were at least two such incident reported.

I will try to post the sound but I do not think iPhone will pick it up.

 

[The_Jeff]

sure it's an alt whine not a belt whine?

 

[JAM25]

Originally Posted By: eljefino
sure it's an alt whine not a belt whine?


+1 i had that issue with my Galant. When i would accelerate the noise increased. Double check on the problem, it may be an easy fix

 

[cat843]

You need to go to a rebuild shop. It could be bearing noise in the alternator. A rebuild shop can either swap yours for a rebuilt or rebuild yours. There may be more than brushes to replace.

And AOHS it could be a belt noise or idler noise or tensioner noise.

If the belt is not new I might try that anyway. If it does not fix it, hey you have a new belt and they wear out anyway.

 

[Kool1]

I would rub a candle on the belt first to determine if the belt is the problem.

 

[Dave Sherman]

Alternator whine can be the stator laminations making noise, too. My Saturn started doing that, just a faint high-pitched whine that got more high pitched as the engine revved up. Increasing electrical load made it louder. Long term prognosis was that the laminations could vibrate more and start shorting windings in the stator if they managed to wear through the winding insulation. New alternator fixed it.

 

[KrisZ]

Since you're not in a panic mode yet, I would simply look for a reputable place to rebuild your OEM unit. It will most likely be much better than cheap, Chinese labor rebuilt alternators found in auto parts stores.

If it were me I would get a good quality rebuild kit and do it myself.

 

[cat843]

Originally Posted By: KrisZ
Since you're not in a panic mode yet, I would simply look for a reputable place to rebuild your OEM unit. It will most likely be much better than cheap, Chinese labor rebuilt alternators found in auto parts stores.

If it were me I would get a good quality rebuild kit and do it myself.


Except that the area the brushes rub against may need to be machined on a lathe.

 

[KrisZ]

Unless the commutator is really badly worn out, light sanding with fine sand paper or even emery cloth or scotch-brite should be plenty enough to clean up the surface.

 

[Chris142]

A bad diode can make it whine but still put out the correct voltage but less amps

 

[cat843]

Originally Posted By: Chris142
A bad diode can make it whine but still put out the correct voltage but less amps


That can be seen on an oscillosope.

 

[punisher]

Originally Posted By: cat843
Originally Posted By: Chris142
A bad diode can make it whine but still put out the correct voltage but less amps


That can be seen on an oscillosope.


....or a DVOM set on "AC".

 

[Wolf359]

I think you're making it too complicated. Just how much is too expensive? Rockauto has a Denso listed for $170 with a $34 core charge. A no name one from AAP is about $173 with a $24 core charge and there's various coupons out there for $40 or $50 off per $100 order, but it still has a lifetime warranty.

I got a run of the mill alternator from the parts store when mine started to make noise. Just didn't want to get stranded with a bad alternator. 80k later it's still running fine. How much are you really saving running around to various junkyards looking for the right part and taking things apart and rebuilding them?

 

[JHZR2]

You're not bad yet...

I'm diagnosing the alternator on the inlaws 02 accord with 58k. It lets the voltage drop to around 12.2v at idle with all loads, though it puts out >14V normally. I looked into the rebuilds at AAP - beware. Their online price with coupon was within $1.50 of the regular store price!!

 

[Smoky14]

Originally Posted By: JHZR2
You're not bad yet...

I'm diagnosing the alternator on the inlaws 02 accord with 58k. It lets the voltage drop to around 12.2v at idle with all loads, though it puts out >14V normally. I looked into the rebuilds at AAP - beware. Their online price with coupon was within $1.50 of the regular store price!!


Sounds about normal.

 

[Donald]

Originally Posted By: punisher
Originally Posted By: cat843
Originally Posted By: Chris142
A bad diode can make it whine but still put out the correct voltage but less amps


That can be seen on an oscillosope.


....or a DVOM set on "AC".


Yes, but when people see your oscilloscope and see you know how to use it they will be impressed. Everyone has a DVM.

 

[Vikas]

The tensioner pointer is at the right location. The belt has about 40K miles on it. The faint whine is between 750-1000 rpm. The alternator has 8 diodes in it. I will check the ripple using DVOM.

 

[Donald]

Originally Posted By: Vikas
The tensioner pointer is at the right location. The belt has about 40K miles on it. The faint whine is between 750-1000 rpm. The alternator has 8 diodes in it. I will check the ripple using DVOM.


The output inside the alternator is 3 phase AC and it uses a 6 diode bridge to convert it to AC. The other 2 diodes may be part of the regulator.

The AC ripple voltage should be under 90 mV. If its over that then you do need a scope.

 

[Vikas]

Honda/Denso put diodes in the center neutral too.

I definitely "want" an oscilloscope! What kind of wallet damage are we talking here? HFT still does not sell one

 

[SubLGT]

Originally Posted By: Vikas
................ I will check the ripple using DVOM.


Unless your alternator manufacturer provides a specification for allowable ripple at a specified current, this test is useless.

http://www.venselenterprises.com/techtipsfromdick_files/updatingyourripplevoltagetutorial.pdf