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70 or 90 amp alternator?

12K views 12 replies 7 participants last post by  MudMagnetYJ 
#1 ·
Auto parts store couldn't advise regarding which alternator was correct, 70 or 90 Amp. 92 Wrangler, 2.5 4 cyl w/o air cond. advice?
 
#2 ·
Your wiring should be plenty good for the 90 amp, that's what I would choose. They came with both, the 90 amp being part of the towing package. I went with s 136 amp, but had to upgrade the wiring to handle it.
 
#3 ·
if it fits as in bolts up and plugs in as stock one did etc then it should be fine to go with the bigger one or smaller. in fact may be a better choice to get the larger one if you have off road lights or goodies to power. higher amps shouldnt hurt anything as electrical items will only draw what they need. if needing more juice isnt a factor id say which ones the best cost would be my pick.
 
#4 ·
higher amps shouldnt hurt anything as electrical items will only draw what they need.
This is true for something that draws amps, but an alternator is transferring amps to the battery. Your power wire from alternator to battery needs to be sufficient gage to handle the amps, and your battery ground to block must be at least the same gage wire as the alternator to battery positive.
The 90 amp alternator should be fine with the stock wire, but it's worth checking out first.
 
#5 ·
For your info:
6 awg can handle 120 amps continues ( I believe this is the stock wire gage from alternator to battery)
4 awg 160
2 awg 210
1 awg 245
 
#7 ·
I would take my old alternator to the parts store along with some way to measure the mounting areas.
If the 90A. alternator will fit, that is what I would buy. On a similar post, one poster found the larger alternator interfered with removing the passenger side motor mount bolt. He suggested switching the motor mount bolt direction prior to installing the larger alternator.
Good Luck, L.M.
 
#8 ·
It's probably too late, but check this out. Tell them '98 Grand Cherokee with a 5.9L Limited. You'll get 136 amps instead of 75 or 90. Mine was a 75 according to my build sheet (get one from Jeep, they will reply in a day or so; you know you are an accomplished Jeep owner when the majority of things on there are no longer on your Jeep), but I put in the better alternator. It's just a bolt in with the exception of the pulley.

From Advance Auto Parts, it's part #13742A.

I had a post on it here.
 
#9 ·
i just got the 98 grand cherokee one all i had to change was the black wire boot on the back the pull also worked it is made for a wider belt just slide your belt all the way toward the alternator i have had no problems had it on for about a week now
 
#10 ·
It would be a good idea to upgrade your wiring with that alternator. I would go with 2awg from alternator to battery+ and from battery- to block ground.
 
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