Paul Waterloo

I too have a Nissan alternator in my 951....it wasn't properly modified to be in alignment with the main pulley so the belt/alternator would make noise. I bought a replacement belt for a STOCK 951 from Pelican, took the alternator off, modified the mounts, and noticed that it appeared that the belt on the car was smaller than the STOCK size belt.

Does anybody know what the size is of the belt that should be used with the Nissan alternator? I'm thinking that the centerline of the pulley (as seen from the front) changes relative to the stock alternator, moving it towards the main pulley, hence the reason for the smaller belt.

TIA

mahoney944

I use a stock belt but I have a larger diameter pulley installed on my Nissan alt. So as the housing is closer, the pulley is still the same

Campbelljj

I'm having a similar problem. After installing the Nissan alternator I saw 12v on the gauge as the car ran sitting on stands. On the first drive the gauge jumped to over 14. On second test run the gauge jumped to just below the red mark on the gauge. I measured voltage on battery terminals and it varied from 13.5 at idle to 15 when revved. On the drve to work yesterday (15 mi) as I got closer to work the gauge dropped from just below red line to about 13.7. Again this was on the gauge. The car sat for 3 months while I did a bunch of work on it. I assumed battery was low and the new alternator was sensing this and charging as needed. Thought all was good. When I started the car to head home the voltage gauge did not move. The needle stayed at rest (10v). Put the meter on the battery when I got home and got 10.2v. Alternator not charging. I think I may have a bad alternator. I plan to measure output from the alternator itself but didn't get around to that yesterday. Any other ideas.

Tom M'Guinn

+1

I used the 6-rib pulley supplied by the eBay seller who sells the Nissan alternator. With that pulley, the stock belt worked fine -- nice and tight.

Glad you got yours fixed. Thinking maybe I should pick up a spare alternator for parts...

mahoney944

For how cheap they are I did. But its probably just a waste. The casing is the only part that's unique because of the mods you do in fitment. All the other parts inside and out can be bought separately for cheap. And they seem to be a solid alternator. I had to fix mine once after it got soaked with water when I was detailing in a hurry. Lesson learned but great part otherwise

Tom M'Guinn

Is that why the voltage regulator failed -- it got wet?

lejams

I installed this alternator mod back in August and have put less than 1500 miles on the car. My experience personally was it was a bit of a bitch. Wrapped it up good and worked together with a machinist to assure that the pulleys were aligned perfectly. The result, it does allow more space for the MAF, so it seemed worth it.

Everything has been good until already last week the headlights were getting dimmer and readings showed less than 12 volts and slowly dropping. I suspected the Alt had gone out, so I emailed the eBay seller telling him what appeared to have taken place. He told me this unit is so heavy duty that in the 15 years he's been selling them, he's never had one problem with them. I think that's a little hard to believe.

He instructed me to check all connections, fuses, and relays, which I did and all are working correctly. I pulled the Alt today and had it tested DOA. He said if it was bad, to send it back at my expense along with $12 for shipping a replacement. Not a good business practice in my opinion for something that should perform longer than this.

Rather than modding another housing and waiting the time in shipping to send it back and receive a replacement, (about two weeks), I prefer to fix this the same way you did. What I don't know and sort of doubt is that since they are internal parts, whether they are available separately.

I just sent him another email to see if he will tell me if I can buy the brushes and/or regulator locally so I can do myself. We'll see what he says.

lejams

Are there any identifiable part numbers on the the ones you pulled from your alternator?

lejams

OEM stock belt worked for me.

lejams

I overlooked your post about buying the parts separately. Can you give a lead on them? When I had the alternator at NAPA for testing today, they could not properly identify this 125 amp version.

mahoney944

You're better off buying a new one from the eBay seller and using it to fix your already modded one. Plus what you dont use will be spare parts for the future.... The voltage regulator/ brushes are all one piece. And with a little bit of tinkering to figure out how it comes out, its fairly simple.

lejams

Thanks, on Wednesday I found a good electric shop. They said it was the regulator and replaced it for $40 while I waited, which was very reasonable I thought. I'll install it tomorrow and hope everything is okay. I'm concerned with what toasted the regulator and whether there is something else going...

Alan 91 C2

Some things to keep in mind about alternators, is there is a stated maximum amperage, say 125A. But this is a peak value, not continuous. And they generally fail due to overheating conditions, in the short run. Long term failures are from brush wear, bearing failure... at 100-150+ K miles.

So for our turbo cars, there is a lot of ambient heat, from the turbo, for the alternator. Porsche installed the air duct to help cool the alternators.

Large power loads in your car, of any kind, create heat within the alternator. Drawing down the battery when the engine is not running, will produce a large current load when the engine starts, and can over-temp the alternator.

So you drive the car, get the engine hot, then run the radio with power amps for an hour. The engine will start, but the alternator is hot, and pushing high amps will take out the alternator.

There are two pieces to making the alternator work:
1. Field current for the rotor
2. Rectifiers for the output current
The most temperature sensitive will fail first, from temperature.