Battery or Alt?

[Mudshack]

Help me diagnose this gang. The XJ seems to run the battery level gauge at the 12amp (amps?) level lately. Then all of a sudden it will drop to just below 9 (bottom of the gauge) and then the XJ dies a slow death in about 5 min. I jump it with my truck and the battery gauge goes back up to 12 again for a while. Then out of the blue, with no indication of anything changing (no clicks, no pops, no jerks, etc) the guage just falls to 9 again and the red indicator "Check Guages" lights up. Only to have the XJ die a slow death in the next 5 min.

I am inclined to think that this is the lack of a working Alternator in the XJ and not the battery. What do you guys think?

 

[old_man]

Personally it sounds like definately an alternator and most likely it took the battery with it, but get them both tested before you blow you money.

 

[Mudshack]

Tested? How?

 

[old_man]

Take them to Autozone. They will test both for free.

 

[Mudshack]

Drive it there as is? Or pull alt and bat. In other words, do they need the alt in the vehicle to test it?

 

[CharlesS]

You would need to drive the Jeep to the local Autozone assuming you think you could make it there....

 

[Mudshack]

I can charge it off of my truck. Then drive there. Hope I can charge it there to drive back home. Lol.

 

[CharlesS]

Before you go to Autozone or what ever the equivalent is.... if I were you I would check the wires that are attached to the back of the alternator towards the bottom.
They are the field signal and source which ECM senses and controls the charging rate of the alternator.
If they are loose or dirty; they can cause the symptoms you are having....

 

[Mudshack]

CharlesS,
I have wiggled and jiggled those wires. Doesn't seem to make a difference. Sure wish you could see where those wires connected without having to take out the alternator. My first problem is having to order a belt tensioner from my local Auto Stealer. I snapped mine off last summer when I was tightening it in stead of loosening it. Come to think of it....I wonder if there is just enough play in the system that it might not be tight enough around the alternator to actually spin it. hmmmmmm

 

[old_man]

To test the alternator, they are going to want it off the car.

 

[techno1154]

If the belt was not tight enough you would hear it slipping when you rev the engine.

 

[Mudshack]

Ah.

 

[Mudshack]

O'Reilly's doesn't have a preference in testing the Alt. So I will charge it up with my truck, then have my wife follow me over there. Hope to get both the battery and Alt testing this afternoon.

Thanks gang. I will tell you what I find.

 

[Mudshack]

Well, she started up and the gauge went right up to 14volts. Stayed there all the way over, even with me turning on CD's, heat, A/C, lights, wipers and turn signals. Started it up for the guy to run the tests, and it only went up to 12volts. The tests showed that the regulator was going out on the Alternator. Then he tested the battery, and it read "Bad Battery."

I started it up and limped home with it barely having enough juice to pull into the driveway.

I have just undone both connections, cleaned out some buildup from the lower connections and reattached everything. Now it is out getting charged up off of my truck. Praying that the build up on the lower connection was the issue.

 

[Mudshack]

Pic of when I know it is not charging fulling.

Pic of when it is dying

 

[ehall]

My jeep used to look like the top pic all the time until I cleaned the terminals on the wire

 

[xcm]

sounds like both the alternator and battery are dead/dying?

sounds like a good time to upgrade battery cables too.

 

[Mudshack]

Well I cleanned both terminals. Charged it and drove it. At start up it goes to 12v and then slowly goes up o 14v. stopped and started it many time over about a 15min drive each time, the same thing. it ends uo pausing at 12v before going up to 14v. i am letting it sit for a whike then will try again if same thing, i will take it to o'rielly's sgain to test it again.

 

[xjbubba]

What year XJ? After 90-91(??), the regulator for the alternator is part of the PCM. Just replacing the alternator may not fix the problem, if, in fact the regulator is the culprit.

 

[Mudshack]

It is a 99 with the 4.0L