Bad Alternator???

Hey guys,

Newbie here looking for some help with what I think MAY be a bad alternator. I have a '99 Cherokee Sport 4wd Auto, 4.0L. This is my wife's daily driver and has right around 157K on it. For the past week or so the voltage on the dash gauge will drop to around 9 and the check gauges light will come on. Turn the vehicle off and restart and it's back around 11 or so and will stay there for a few minutes and then drop back to 9. I pulled the alternator and took it to the parts store and they tested it and it was putting out 15 amps on the machine. Brought it back, bolted it up and it was sitting on 14 on the dash, running about 13 on the handheld voltmeter with the radio, lights, and A/C on. She comes home today and says the lights on again. I start it, 14 on the dash. After letting it idle for about 10 minutes the light was on and this is what I got with the handheld at the battery:

w/ A/C on 7.4-9.9
A/C off 8.9
with the car off 11.7 at battery
@ restart 11.4
after 30sec 8.8

Is this thing going bad or should I look elsewhere? Thanks for any help and experience you can share!

-BDHershey

It's probably failing, maybe internal corrosion or dirt on the brushes

abc20abc said:

Instead of making a thread I figure why not just ask it here first... Why won't a <91 alternator fit a >91? is it because HO?

Click to expand...

More info. a 91 fit a 91 ho is this your question???


Nick

abc20abc said:

Instead of making a thread I figure why not just ask it here first... Why won't a <91 alternator fit a >91? is it because HO?

Click to expand...

RENIX engines use Delco alternators, HO engines use Nippon-Denso

abc20abc said:

Instead of making a thread I figure why not just ask it here first... Why won't a <91 alternator fit a >91? is it because HO?

Click to expand...

Pre-91 is a conventional alternator with a built-in voltage regulator. 91-up has no internal regulator. The regulator is part of the engine computer.

This is me as well...What happens is it will hover around 11-12 and after a minute or so of driving, will hit 9 and the Check Gauges will light up. Also, I sometimes, more now anyways, get a squeal when I start her up in the morning. Once that stops, it often go to 14 and stays that way.

I put a new AC comp on a few months ago and replaced the belt at that time. Seems like I started getting this problem after I did that...

Help!

copper_blue said:

This is me as well...What happens is it will hover around 11-12 and after a minute or so of driving, will hit 9 and the Check Gauges will light up. Also, I sometimes, more now anyways, get a squeal when I start her up in the morning. Once that stops, it often go to 14 and stays that way.

I put a new AC comp on a few months ago and replaced the belt at that time. Seems like I started getting this problem after I did that...

Help!

Click to expand...

Check to make sure your belt is tight enough. I just went through something similar a couple of weeks ago. I got my Jeep back from the body shop, and they had the belt off to inspect some things and didn't put it back on tight enough (you'd be surprised how freakin tight the belt needs to be!). My voltmeter was slow to come up to 14 when I cranked it up, and the belt would often squeal like crazy. I was going to get a new belt anyways, but to last me the rest of that week I just snugged it down some more, and everything worked good.

Hey Thanks! I'll give that a go tomorrow!

Oh, by the way it did turn out to be the alternator was bad. I'd died on the side of the road two days later. Swapped out the alternator and replaced the belt and all is good to go. I though the A/C compressor might have been going too as the wife was complaining the air was intermittent, but it must have been a voltage issue, cause it works fine now. And the belt did have to be really tight!

-BDHershey

This morning was the worst so far. It squealed really bad for most of the trip to work. squeal sounded more mechanical, but still had that high pitch as I pressed on the accelerator.

I bet the neigbors are pissed at me!

Anyways..Do you recommend getting a JY replacement or shoud I spend the money on a reman from Advance/ Auto Zone/ Murray's ?

copper_blue said:

This morning was the worst so far. It squealed really bad for most of the trip to work. squeal sounded more mechanical, but still had that high pitch as I pressed on the accelerator.

I bet the neigbors are pissed at me!

Anyways..Do you recommend getting a JY replacement or shoud I spend the money on a reman from Advance/ Auto Zone/ Murray's ?

Click to expand...

Are you sure your belt is on tight enough? I changed mine, and thought it was on tight enough. Not even close. I had to really crank that sucker down.

It's not floppy, but it's not military bed tight...I can push it down a little bit with my index finger...

If I were in your shoes, I'd try tightening the belt down just a little bit more. I know I was surprised how tight it needed to be; I felt like it was too much.