battery light is on?

[lapisxj]

Here in the past week or so I have noticed the battery idiot light has come on in my 96 XJ. I have had the battery checked (good), I am getting decent output from the alternator (13.6 ish), I just cleaned the connectors and all that jazz. So what triggers this and what else am I overlooking?

 

[Ivan]

I'm not sure if this would apply to yours (check your owners manual), but later model XJ's have a battery temperature sensor located in the battery tray.

From my FSM: "This sensor is used to monitor battery temperature. This temperature data, along with date from montitored line voltage is used by the PCM to vary the battery charging rate. This is done by cycling the ground path to control the strength fo the rotor magnetic field. The PCM then compensates and regulates generator current output accordingly."

Maybe this will shed some light on your problem.....

Ivan

 

[lapisxj]

Can anyone confirm this? I have a 96 model and I didn't see anything in the manual or coming off the tray. It is still acting up.

 

[Joe R.]

If 13.6 is all you are getting from the alternator then that is not that good... sounds like the alternator is getting tired. You should be getting around 14.6V. A quick check for the battery condition would be to turn your headlights on and start the engine. If the headlights get dimmer, it is time for a battery. But if you say the battery has been load tested, then this shouldnt be the problem. Also look for loose battery connections. Sounds to me like the voltage regulator might be going bad in the alternator. If you have access to a Vat 40, or similar load testing device, have the car running and load the battery down to 12 Volts, Then read the amps of output. This is an easy way to tell if the alternator isnt putting out what it is supposed to.
~Joe~
See, college is paying off.... hehe