Hi there I have been reading up on this site on reasons why my battery light is on. I have a brand new alternator installed along with new + battery cables and I cleaned up the ground cable around the terminal and also have replaced the battery. I have seen the alternator charge between 14.5 and 15 volts a couple of times but the rest of the time its between 12.90 and 13.15 volts. The battery light goes off once in a while. Please help getting frustrated.

 

It sounds as though you have a high resistance connection in the charging system. Take the car out for about a 10 ride and then park and lift the bonnet and check the battery terminals for heat. You should be able to touch them with no more heat than normal under the engine compartment. If one of them is to hot to touch then allow it to cool and then polish the terminal and the post and reconnect.

 

Avern1, I have polished and cleaned up all the terminals and none of them heat up, battery light is still on

 

Actually i have same exact problem, i have a scangauge that shows battery voltage when start up engine gives around14.8 to 15.2 v , then after a while (5 to 10 Minutes) drop down to approximately 13.2 to 13.4 in best situation....what is the issue ?!?!
Thanks

 

That may be the smart charger. But use a voltmeter at the battery to be sure and do the job right

 

@ Jordan, voltage you are seeing is normal.

@2002 Could still be a bad negative cable (as you state you replaced positive). Also, as I understand in research, Jaguars are very sensitive to voltage fluctuations (hence battery causing lots of problems) & some members have stated that using a non-Jaguar alternator "alternator will still put out the correct voltage but will be rejected this will not cause a problem but that annoying batter ind. light will be on unless you have the jaguar alternator"

Next questioning the field wire between the ECU and the alternator. If this wire has a break in it, it can be affected by heat and vibrations and cause the voltage to fluctuate between.

Per Thermo to test this =
if you look, you should see an orange/green wire going to the alternator on the 3 wire plug. This is the field lead. To measure this lead, I would say to get a sewing pin and then slide it along the insulation of the wire into the plug. You should feel it hit the pin inside the plug. From there, you can use a set of alligator leads to hold the pin and then with the motor running, push the pin in to get a reading. Under minimal load, you should be seeing in the neighborhood of about 7-8 VDC. If you turn on a lot of electrical stuff (dash fan, headlights, rear defroster), you should see it jump up to about 10 VDC. As you are watching the voltage, if you can have someone else wiggle the wiring harness, if the voltage starts jumping wildly (more than 1.0 VDC), then that part of the harness has an issue with it. If you get 0 VDC out and the dash is reading 12 VDC, then odds are the wire between the generator and the ECU is bad or the ECU is bad. If the wire is up at 12 VDC along with the dash, then your problem is internal to the alternator.

 

The smart charging requires the appropriate kind of alternator. Using a typical one will cause the light to be on.

 

Hi Jagv8,

Does it require also the appropriate Battery ?! If yes what would it be ? I mean CCA, Ah ? Specific brand ..etc please specify. Thanks

 

 

it's aimed only at lead acid. Don't use one that's too puny but otherwise any.

 

Jagv8 is the one I have to puny?

 

Don't know - what does the car need?

 

You say battery light is on, is it the one with a battery symbol????

I have the same problem , if you mean the battery symbol?

It comes on once in a while, checkd voltages both at battery when running.

I just ignore it for now.
Walter

 

I got codes read on the car and its p1146 (Generator C line low input) does anyone know what color that wire is? This is the wire diagram