Thread: B15 SE Alternator vs G20 Alternator - Why can't you swap them?

My girls 2000 Sentra SE ABS light kept coming on randomly so I took it out for a drive. The radio would shut off the same time the abs light would come on. After awhile the battery, ABS, and brake light started turning on and off. So I took it home and put a meter on it. Sure enough it is the alternator was going high. Runs 14.5v idle and 15.5v at 2000 rpm and keeps going.

I tried 2 different 1999-2002 G20 90A alternators and they seem to work but the battery light stays on. Has anyone got one of the G20 alternators to work and how? Guess I'm going to look in the FSM's and see if wiring is different. The Sentra 100A has the same connector but the frame is slightly different. It all hooks up fine just the annoying battery light for some reason when I use the 90A

Also going to hit the junkyard and pull another 100a.

100a out of what, a quest?
Iirc, the regs are 80a b13/14, 90a b15/g20, 100a quest

B15 SE - 2000-2001 2.0L SR20. The SE came with a 100A alternator, and the 90A doesn't seem to work in place of it. The original alternator shows 100A and rockauto shows the same.



ACDELCO 3341370 {#19134363} Professional; Remanufactured; 100 Amp
0050A; 334-1370; 6Y1; Amps: 100; Clock: 12:30; Internal Fan; Pulley: 6S; Internal Regulator; Unit Mfr: Hitachi

REMY 12266 {#231004M800} Premium Remanufactured
100 Amps


Edit: That's really where I'm going with this, I thought the B15 SE cars were pretty much the same RR drivetrain and components to the 2000-2002 G20 RR cars. But am finding there are a few differences like Alternator and EGR stepper motor so far...

You may have a wiring fault, and not a problem with the alternator. First, make sure that the ground wire is attached to the alternator, there should have been a separate wire that attached to a small bolt on the alternator frame, likely going to the chassis or a motor mount. This needs to be in place, or you can see a higher than normal voltage being output.

If that's in place, you will need to take a volt meter and check for battery voltage on the 2 wire connector plugged into the alternator, wire might be yellow, may be different on your year, I don't have a manual handy. This is a battery sense line, and tells the alternator what voltage the battery is seeing when charging, this line regulates the output of the alternator. If the voltage level on this line is too low (less than 14v, give or take), the alternator will try to put out a higher voltage to keep the battery charged.

The other wire on that 2 wire connector is what would light the Battery light on your dash, you should only see voltage on this one with the car running, so be careful measuring that. This wire should be around 14.4v (give or take) with the car running. This line is only important for the idiot light on the dash, and would not be part of your problem, I'm just including this here to be complete.

Nissan has grounded the alternator via a separate wire on many cars, maybe there isn't sufficient grounding via the engine block, I don't know. But our cars have had grounding issues in other areas, so this probably isn't any different. For fun, take a volt meter, and check voltage between the alternator case, and battery negative. If you see more than about .1v, then you've got a bad ground to the alternator that needs fixed.

Good advice.

The 00-01 SE doesn't have a grounding wire. Just the standard 2 pin plug and 1 wire output. Should get to testing the alternators tonight. Pretty sure the regulator just went bad but we will see.

I also picked up 3 more alternators out of the yard today. A 00' SE just like mine (100a), a 00' B15 1.8L (100a) and a 00' Altima 2.4l (100a) the B15 1.8l and the Altima are close if not identical to each other but mounting is clocked different. So they carry a different front and rear case but same regulator on all 3. They are also the newer type alternators unlike the 99-02 Infiniti G20 90A which are an older type of alternator that is different in quite a few ways.

OK, they must have finally eliminated the separate ground connection, you've obviously seen a few of these lately if you've pulled them off of cars in the salvage yard. I'd still run a voltage drop test between the alternator and battery negative just to check.

If the battery light is on, as you reported originally after changing alternators, then the alternator is outputting (via the 2 pin connector) little or no voltage, causing the light to stay on. I'm not sure at what voltage level the light goes off, but once the alternator is close to 12v, then the light should go out as the voltage difference won't be enough for the light to stay on.

I'd stick with the SE alternator to match what you had originally, and see how that works. It's entirely possible that another alternator from another model may fit, but the wiring on that connector may be reversed, meaning that your battery light would always be on, and the alternator wouldn't have its battery sense input, and would constantly output higher than expected voltage. Without comparing wiring diagrams for those specific models, I can't be sure.

Perhaps adding a grounding strap won't hurt. The reman alternator I got from rock auto came with the little bolt to ground it. Defnately need to perform a voltage test though. I suspect it's not just the alternator, a 90a should have worked just fine as the light goes by voltage and not amperage, and the alternator is regulated. Pull fsm and look up charging.

Http://www.nicoclub.com/FSM/Sentra/2002/sc.pdf

A strap probably wouldn't be a bad idea.

The other night I installed 2 different G20 90a alternators and they both seemed to work but the battery light stayed on. I went to the junkyard and grabbed 3 different LR1100 100a to test. Well I got home tonight and started thinking what Jimbo SE-r was saying about the wiring may be reversed and thought I would check before I removed the 90a. Wiring is exactly the same between the G20 and B15 SE. Started the car to put it in the garage and the battery light wasn't on... So I just put everything back together and drove it around and kept checking the voltage. So far so good. I'm guessing either the 2 pin plug had bad contact or the ground had bad contact. So the 90a and 100a seem to be compatible. I'll just keep running the 90a until I have a problem. Maybe I'll check the other 100a alternators out in the G20's and see how they work out.