Alternator started whirring...

[DAYTA]

The alternator on my 97 NSX (~70k miles) started whirring really badly today, so it sounds like I have 2 main options:

1. Purchase a new OEM unit
2. Have my existing one rebuilt

Per other threads I've read, it sounds like sourcing a new unit has been very difficult for folks recently so I'm not even sure that's a viable option. This leaves having my existing one rebuilt, but I'm not sure where to find a reputable shop who can do the work (I live in CT).

Is the NSX alternator specific to our cars? I am hoping not in which case we could utilize a new unit from another Honda/Acura model of the same era (vs rebuilding an old unit).

 

[Old Guy]

I believe that the NSX alternator is specific to the NSX which is why both new and rebuilds are close to un obtanium; but, I also believe that there are other alternators that can be made to fit.

If the only issue is whining that is likely bearings and that is not a difficult repair. However, while I am in there I would probably do the brushes also. This is not high precision surgery, particularly a bearing replacement. An internet search will get you lots of vendors claiming to do repairs close to you. However, check out the 1991 service manual starting on page 23-107. No special tools required other than perhaps an impact wrench. You don't even need to separate the pulley from the alternator if it is the rear bearing. A little scrounging with Mr. Google will get you a couple of reputable vendors selling bearings, brushes ... if you want to do this yourself.

 

[docjohn]

I'm not interested in DIY for such things, so If you don't want to take it on, ask your parts/service managers If they know of someone in your area that does. I got a list of guys that do that on the side, but I got a very low mile one from another primer. The other interesting tidbit, If you know anyone with a comptech supercharger they may still have their old one lying around as the blower required the opposite rotation.

 

[drew]

Rebuilding is an easy DIY. I have thread on parts interchange.

My whirring was the diodes and quality CN replacement is < $20 and takes an hour to install. Bearings are a few dollars for OEM.

It will take you less time than finding a shop.

 

[DannySX]

Rebuilding is an easy DIY. I have thread on parts interchange.

My whirring was the diodes and quality CN replacement is < $20 and takes an hour to install. Bearings are a few dollars for OEM.

It will take you less time than finding a shop.

It would be cool to see some DIY write-ups and videos of that.

 

[drew]

Almost any Nippon Denso alternator rebuild video will work

NSX Health Check Service - Page 39

Hi, all. Addition to my NSX Climate Control Unit (CCU) service, I have been offering the NSX Health Check Service for some of the members here. As I received similar questions on this, I would like to share some of the information of the service and the maintenance works carried out...

www.nsxcb.co.uk

Post in thread 'Has anyone rebuilt an NSX Alternator?'

14 August 2023

To replace bearings: just need a small 2-jaw puller to get the small bearing side apart. The puller gracefully separates the casing halves.

I tried to use hand tools to remove the pulley and failed. The shaft hex and nut are difficult to get access too. So I used a impact gun and the nut loosened without issue. I also used the impact wrench to tighen the nut, so hopefully I didn't make more difficult for my future self.

I was trying to fix a whine, the existing bearings felt good, but went for the bearing change because I had them. Didn't fix, but everything is much cleaner now and the...

• drew

• 

this one looks very close to the NSX using basic tools

 

[DannySX]

Almost any Nippon Denso alternator rebuild video will work

NSX Health Check Service - Page 39

Hi, all. Addition to my NSX Climate Control Unit (CCU) service, I have been offering the NSX Health Check Service for some of the members here. As I received similar questions on this, I would like to share some of the information of the service and the maintenance works carried out...

www.nsxcb.co.uk

Post in thread 'Has anyone rebuilt an NSX Alternator?'

14 August 2023

To replace bearings: just need a small 2-jaw puller to get the small bearing side apart. The puller gracefully separates the casing halves.

I tried to use hand tools to remove the pulley and failed. The shaft hex and nut are difficult to get access too. So I used a impact gun and the nut loosened without issue. I also used the impact wrench to tighen the nut, so hopefully I didn't make more difficult for my future self.

I was trying to fix a whine, the existing bearings felt good, but went for the bearing change because I had them. Didn't fix, but everything is much cleaner now and the...

• drew

• 

this one looks very close to the NSX using basic tools

Thank you for sharing.

 

[Spoolinfool]

Dc power has our application and its brand new with 180amps.

 

[Jerry@Mobile]

I agree with the diode failing. It happened to mine in my 2000. I took it to a local alt./starter shop and he tested it in front of me. There are different diodes that correspond to different RPMs of the alt. Mine would drop out below 2K engine RPM. It also had the tell tale whine like a bad bearing. It was the diodes. While in there, the bearings were changed out as well. Jerry

 

[nis350]

Rebuilding is an easy DIY. I have thread on parts interchange.

My whirring was the diodes and quality CN replacement is < $20 and takes an hour to install. Bearings are a few dollars for OEM.

It will take you less time than finding a shop.

Do you happen to have the part list and where to obtain them if I were to refresh the oem alternator (NA 3.0)? Thanks.

 

[DAYTA]

Outside of basic maintenance stuff like oil/fluid changes, I'm admittedly not that mechanically inclined/confident like many of you guys to tackle a DIY alternator rebuild.

I did call SOS who advised to remove the alternator belt to determine if the whirring/whining went away to isolate the source of the issue. Fast forward to me unable to get enough leverage to loosen the bolts/tensioner so I could remove the belt...

However, when I turned the car back on the whirring/whining was strangely almost entirely gone - not sure what this means? If it was the bearing, I would have expected the noise to remain consistent. But now that the noise is not there, I'm wondering if there is still an issue with the alternator or if it was just an anomaly.

To confirm, I have not experienced any electrical issues yet - I just noticed the whirring/whining noise previously coming from that side of the engine.

 

[drew]

You're gonna need to get the belt off to better diagnose.

FWIW the symptoms sounds like the rectifier.

....

The complete parts list and interchange is in the "Has anyone rebuilt..." link.

Parts are going NLA so secondary suppliers, Amazon, AliExpress, and eBay are required.

Some NA2 alternator parts are available and work just well in the NA1.

 

[DAYTA]

Coordinated with Chris @ SOS and they actually had one rebuilt alternator in stock for the 95-05 (they have 3 in stock for 91-94 as of today).

Order placed and the unit should arrive next week - easiest and most complete solution as everything will be rebuilt (per SOS website):

• Tear down, cleaning, and bead blasting the case and end plate.
• Replacement of the rectifier, regulator, bearings, and brush holder.
• Cleaning and testing of the rotor and stator.
• Cleaning and machining of the slip rings.

 

[drew]

Ask SOS for your old regulator back. The regulator is NLA, expensive, and is probably OK.

You might consider requesting the Denso sticker stay in place and not get removed during bead blasting.