I have a 99 xj... Parked it at school today and went to start it and no electronics at all... Jumped it, ran it for a while drove home and same thing happened. I have optima red top. Any ideas? My horn has been weak the past month or so If that helps at all...
Thanks david

 

you made it all the way home and it died? or you got home, shut it off and it wouldnt start again?

 

sounds like an alt. problem.

 

easy way to test the altenator. start the jeep. let it run for a second. while running disconnect the battery. if it stays running its not the altenator its the battery.

 

I would start by cleaning all the connections check all cables and then take the battery out and testing it first. Sounds like you have a quality battery but youy never know you could have a faulty cell or something. If no luck after all of that you might need to pull the alt and have it tested.

Start with the easy stuff!

 

Made it home and tried to restart it with no luck at all

 

I have been told numerous times that doing this could burn the alternator up.

I have never tried so I cant say from firsthand experience. Anyone else?

 

Battery bad, ive already had one optima bat go bad. I have had several batteries be fine, park and gio to leave and wont start. if a battery gets a dead cell its done.. I just had one 3 years old go bad 2 days ago. Put a voltmeter on it see what you get and try and start it and see what it drops to

 

it can yes, but only if you leave it running forever. i dont want the guy to drive around just unhook it. if it runs for more then 10-15 seconds then its the battery for sure.


just by the symptoms it sounds like battery 100%

 

sounds like batt to me

 

Its a bad battery and optima batteries are free replacement s for three years but mine hasn't been marked when I bought it so idk what I should do... What optima would you guys recommend red or yellow

 

Pull the alt. and have it checked, if it is bad it isn't putting out enough to charge the battery. If your battery is a good one it will hold a charge that will run your engine for a long time but not have enough juice to power the starter. So have the alt. checked first.

 

I'll replace the battery first since its free and if that doesn't work then ill try the alternator

 

Glad you figured out which it was. My 99 had the exact same thing a few weeks ago with my Yellow Top. As far as which to get, it depends on your needs. If you have (or are planning on having) aux lights, a winch, sound system, etc, I'd go Yellow Top. If you do a lot of short runs and you constantly turning your XJ on and off, I'd go Red Top.

 

The practice of disconnecting the battery while the engine is running is very bad and can cause a voltage spike and fry the PCM.

Sounds like a bad battery, if you jumped it and it stayed running after you took the cables off, the alternator is charging.