Originally Posted by wisteriaaa
So i did the test, and sure enough the voltage gauge bounced back and the lights/heat got much brighter and blower motor was faster. Should I just get a replacement 90A alternator? I've seen lots of people here talking about getting grand cherokee or wrangler sahara 120A alternators and installing the with no problem. I have the 4.0L engine.
Now, before you go ripping out and upgrading your alternator the next big question is; What condition are your battery cables and cable ends? Just because they look OK means nothing. If they are original I would toss them out and replace them all.
They are probably loaded with green corrosion under the insulation. That sets up high resistance. This high resistance can reduce the amperage output of an alternator and causes dimming lights and large swings in the amp gauge readings plus
premature death of your alternator.
Think of corrosion as if it was a choke hold, cutting off the free flow of the electrons along the copper wire surfaces
right where the corrosion resides.
Disconnect both battery cables and lock onto each battery post connector with a pair of vise grips. Now twist each wire at least one full turn in each direction three or four times and then hook them back up. Now run the same field test I mentioned earlier.
Did you see any improvement? if you did then your wires are all crappy inside and need replacing. And your alternator may be alright after all!