According to the fellow members of clubxterra.org you can upgrade the Nissan Xterra alternator, which is a measly 85 amps to the 115 amp alternator from the Nissan Quest. (that's a 35% increase for your fellow stat lovers) Depending on which year in the 1989 to 1992 compatible date range, it can be a direct swap or require a minor amount of grinding to get it to fit.
The motivation behind this upgrade stems from the fact that I added a total of six (6) 55 watt Hella 500FF lights, four drivers for the roof rack, and two fogs for the bumper. When I turn on the roof rack lights the engine groans and changes pitch like it has to work twice as hard. When I eventually get some surround lighting or rock crawl lighting or a PA system I’ll tax the alternator even more. So I figure I might as well do this cheap upgrade.
My friends and I took an alternator-hunting trip to Harry’s U-Pull It yard in PA. Out of the thousand or so cars that we canvassed there were only two matches and one of those looked half descent. It ended up costing around $16 plus a $3 core and we scored a bunch of other random bits and pieces of trim that I needed from a 2002 Xterra so the trip was well worth it.
The first step after acquiring my new project alternator was to get it tested at my local auto store. They have a dedicated alternator test cart where they put the alternator in a vise-like apparatus, connect some electrical leads and then attach a drive belt. They run it for a minute or so and determine the average voltage output. Your average alternator should be putting out around 14V (yes cars have 12V electrical systems, but this is directly out of the alternator before it’s reduced/capped) but mine was putting out a whopping 10V. Of course it couldn’t be that easy.
So the next step was to take it apart and see if I, having no experience with alternators, could see an indication of why it wasn’t producing full volts.
Teardown:
1. Remove the bolts holding the two halves of the alternator together. One half includes the coil and is the stator. The other half includes the bearing support for the rotor.
2. Pry the two halves apart. This is much easier said then done. I ended up standing with the stator half down and pulling on the rotor pulley. Needless to say when it came apart I nearly fell over.
3. Remove the two bolts located at 5 and 7 o'clock positions that retain the brush housing.
4. Using a soldering iron melt the solder connecting the two tabs to the rest of the alternator. This was by far the trickiest part. It was a very high temperature solder and I had to hold the soldering iron on for a good 30-60 seconds before there was enough residual heat in the part for the solder to turn liquid. I then had to scrape enough of it away from the tab connection and use a pair of plyers to make sure it remained disconnected as the solder solidified.
5. Remove the brush housing. You can clearly see the broken portion of the brush in this picture.
6. After removing a rubber endcap it exposes the two terminals which the correspond to each of the two brushes.
7. Once again I had to use the soldering iron to melt the solder in order to remove the brush-spring-contact assembly. Interestingly, the brush is formed with a copper wire coming out of it which travels in the center of the spring and connects to the metal tab at the bottom. I guess the spring connection wasn't sufficient (or efficient) enough to conduct the power.
8. Originally my buddy Alex had suggested that I get some graphite (the material the brushes are made out of) stock and cut/shave it down to size to replace the broken brush. But seeing as they have integral wires I don't think that's an option any more. Now I need to figure out where I can get a rebuilt kit or parts for the Quest Alternator... ideas?
