for the record it ran fine and then when it got to 20-30 degrees this hapend
ill go in order of what happend
1. battery dies
2.jump car battery works
3.drive jeep to have it shut off 2 miles down the road.
4.jump jeep,let battery charge,dies
5.leave jumper cables on car let it charge for 20 min drive home
6.replace alternator with BRAND NEW 1
7.jump car....dies....
8.replace all 4 power relays...dies
seems like it well run with the power that the battery has but once its draind it dies
its a 1989 4.0 with nothin on it. its been through some puddles but nothing it couldnt handle.

weve checked the wires leading to the alternator and there connected,and it has nothing to do with the battery because once we start it and take the battery cables off it dies, once its under its own power the alternator should kick in...
All help is appreciated and walking from fort dix to mcguire air force base is a ***** when its 20 degrees thanks alot
A1C delpha

 

I went through this Goat Rope with my son's 87 Renix XJ. We replaced starter, alternator and battery only to realize we had the problem, still. Have you checked the condition of your battery cables? I don't mean just at the battery and the starter. Check both the positive and negative cables starting at the battery and trace them both through their entire length looking for nicks, cuts, crimps and shorts. Or if you're sure this will fix it, Just replace both of the battery cables. Judging by what you have already done, i believe this will fix your problem. Hope this helps.

 

but once the jeep is started the alternator should keep the jeep running,even with the battery being unplugged correct?

 

Try cleaning the connections for the cables as well. When you get your jeep started take a volt meeter and see how many volts the alt. is putting out at idle then at 1500 or so rpms. I would also hook the voltmeter to the battery to see if its getting the charge as well. Another thing to do is have someone try to start the rig when you have the tester on the battery to see if it drops allot, like to 8 volts or so when you turn your ignition key.

 

sounds like it isnt charging....you need to put a meter on the back of the alt at this point..if you find no voltage i would be looking into your stator signal going to the alt...Most of the time they come from the key switch.....

 

Yep. I would test the alternator. Or take it back n have whoever you bought it from test it. Just cuz its new doesn't mean it works. I've had that happen plenty of times with plenty of parts

 

could be a bad ground

 

x2 on just cause its new dosent make it good i have had to return many of rebuilt parts to napa macays and the zone as a mater of fact when i took the alt back to the zone both they had on the shelf where bad also

 

1) Check grounds - particularly the cylinder head-firewall ground. That one often causes trouble on 1987-1990 rigs.

2) Please, for the love of Gawd, stop "testing" your alternator by pulling the battery cables while the engine is running! That was fine on old Chevvies and such, but there are enough electronics in vehicle since 1975 or so that doing that sort of thing is a stonking bad idea. When you pull the battery cable, it generates a transient spike in the system - which can blow out solid-state electronics! This is an example of a valid test that is no longer valid, and you should stop doing it.

3) If you look at your positive battery cable, you'll see two cables exiting the clamp. One is a large cable that runs down to the starter motor, and the other is a slightly smaller wire that runs to the starter motor relay screwpost. At that point, the electricity gets branched off (vy way of fusible links) for primary distribution.

I bring that up becuse some time ago, I had a similar problem with my 1987. Turned out to be corrosion at the clamp for this small-gage lead, and it wasn't making effective contact all the time. This would result in random stalls, and it was a pain to locate. I finally found it by "wiggling wires" - the corrosion was all under the wire jacket, and couldn't be seen easily.

So, I made a set of cables, and that took care of that. It was that set of cables that got me started with WiP, as I recall...

 

thanks all...ill have results at 5pm hopefully
HAVE A GREAT WEEKEND!!

 

And don't forget you can run a car all day long, alternators have to be above a certain RPM to actually reach an output that will run the car and charge the battery...Usually around 1000-1200RPM is when it will kick in...

 

I agree with 5-90, Bro. I grew up with old chevies and my dad showed me that pull the battery cable trick to test the alternator. I had a 1980 Toyletta truck and gave that little trick a try. It took out the alternator, solid state regulator and ignition module. It was a VERY costly lesson learned. Your new alternator probably was good until you pulled the battery cable. Take it back to the store and have them test it. If it's bad just play the part of it being bad from the store....and DITTO DON"T DISCONNECT THE BATTERY TO TEST ALTERNATOR OUTPUT!!!!!

 

around 12.8V-13.5 Volts at idle is healthy its the amperage that increases with the RPMS........

 

well as promised(although late)the update is that napa is ordering me another 1...if this one doesnt work(cuz they cant test it) then i must have a wire loose or broken someplace

 

Do like I said above. It will let you know if its bad or not without removing it unless you have already.