Back to Index of all TutorialsIntroduction- You should be able to remove alternator without removing anything else as long as you remove alternator from bottom. You will have to remove the cover that protects bottom of engine if it is still in place. I would say this removing alternator is pretty easy.
Buying alternator:
The best price is likely from a shop that specializes in rebuilding alternators and starters. listed under auto electrical in phone book. There is normally a refundable core charge. you could also try junk yard if you are short of funds. Ebay seems to have very good prices.
Procedure for removing
1. Disconnect the negative battery terminal.( VERY IMPORTANT IN THIS CASE)
2. Disconnect black wire at (labeled m)alternator with 8mm wrench. Disconnect white wire with 10mm wrench(labeled battery). Unplug the main alternator plug.(squeeze to release)
3. Back off the tensioner bolt a bit to give yourself some room. Use 14mm socket and access from the top.
4.Completely remove the bolt that connects tensioner to alternator. Your tensioner will now be dangling a bit.(access from under car)
5.Completely remove the pivot bolt with 14mm socket (access from under car). There is an odd shaped nut at the other end. The bolt only threads into this nut and passes through alternator and alternator bracket without any threads. You will need to use a small locking pliers on bolt and hit with rock to get bolt out. The lower fan shroud will get in the way a bit but you can do this without removing shroud.
6. I used a small rock to bang the alternator off the alternator bracket. The alternator than comes down through the bottom. You have to twist the alternator to steer it out to freedom.
7. Reinstall is reverse of uninstall. Use a screwdriver to help align the hole for pivot bolt. clean pivot bolt so it slides easier.
End of removal instructions
Description of pivot bolt and tensioner:
There is a 14mm bolt at bottom(alternator pivots on this bolt) and the two 14mm bolts associated with tensioner at top. The bottom bolt(pivot bolt) and the bolt that locks tensioner to engine , face front of car. The bolt(long bolt) used to adjust tension is accessed from passenger side of car.
You dont need to pry the alternator to tighten it. Tightening the tensioner will tighten the belt. Once you have tightened the tensioner, the alternator is fixed in place. The pivot bolt and the tensioner locking bolt can be loose and the the alternator will still be fixed in place.
IMPORTANT you have to back off the tensioner and loosen the pivot bolt and tensioner locking bolt before alternator will move to allow removal of belt. Three things to loosen before the alternator is free to move!
Belt deflection specs:
ALTERNATOR:
-belt deflection with engine cold mm(inches)
.....max limit 11 (0.43)
.....adjusting used belt 7-8 (0.28-0.31)
.....new belt 6-7 ( 0.24-0.28)
pivot
top of alt
Alternator bracket. One per car of course. bracket is connected to engine. You can put end of hammer handle on square nut and push the alternator back to tight position and vice versa.
from 1991 factory service manual
Note that there are two types of alternator so confirm which is for your car:
hitachi Alternator
Mitusbishi alternator
Links
alternator testing
http://jgdarden.com/batteryfaq/carfaq5.htm
Modified by vancouverbc at 11:36 PM 2/2/2009
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Modified by vancouverbc at 1:01 AM 3/5/2009
Modified by vancouverbc at 2:15 AM 3/5/2009
1989-1998 240sx TUTORIALS
Factory service manuals 3
Factory service manuals BEST
Factory service manual2
Factory service manual 1989
Old FAQ
INSTALLS
Pictures of parts
I tried to modify the battery connection and the harness plug but it didnt work. 
My battery light turned off but it wasn't charging the battery at all. So i picked a new one up and started all over again. I wanna add a little more for a better understanding on what else is needed for the removal of the alternator while its still in the car. For starters you cant just remove it from the bottom because the sway bar is in the way and if you try to go up and forward your fan and shroud get in the way. So to make it a easier i loosened up the power steering then i removed the intake. I then proceeded to remove the shroud then the clutch fan. Its probably more tedious this way but less stressful for me. Its best now to disconnect the battery and the harness plug and the ground if you haven' t already. Next i started to loosen up the alternators tension bolt then i unbolted the top bolt then the bottom bolt. Once you got them off try to move it to loosen it because chances are that thing is in there tight. Once you've got it loose enough to spin it rotate it counter clockwise so it will spin off the mounting brackets. Now this is where it got a bit tricky for me. Trying to pull it down seemed the likely route but there wasnt enough room to pull it down. So thats where that whole removing the other stuff comes in. If you can try and twist it a little so you can pull it down and towards the right, in front of the engine. If you played you cards right you should be able to pull it up and out after a little maneuvering. Once its out make sure everything looks identical between the two alternators. And to install do steps in reverse. I hope this helped because when i read this the other day it wasnt very clear about certain things. If i left anything out please feel free to add.