Hello Forum
I have not been in for long period of time my 04 is running well.
I replaced the Alternator and the Battery light stays on.
It shuts off at startup then come on and stays, Is there a way to reset this, resetting the computer has not worked.
Here's the kicker. scan tool has 14.2 volts all the time drops to 13.9 maybe.
Food for thought.

Smity

 

Sounds like an incompatible alternator. There are other posts, I suspect, about this.

 

Sorry; as I said have not signed in for a while.
3.0, Auto, 120 amp alt.
I will know need to know what makes it incompatible.

 

If the alternator is not an OEM one (like cheaper internet buys) it does not have the ability to do the 3 charging levels. Just because it's 120 amp does not indicate it's a Jaguar OEM.

DefaultVehicles With 2.0L, 2.5L or 3.0L Engines

The charging system consists of a 120 amp output generator and regulator assembly which generates current to supply the vehicle electrical system with electricity when the engine is running and maintain the battery in a charged condition.The generator is belt driven by the accessory drive belt.

When the engine is started, the generator begins to generate alternating current (AC) which is converted to direct current (DC) internally. The DC current and voltage is controlled by the voltage regulator, (located inside the generator), and then supplied to the battery through the main battery positive cable.

The generator is solidly mounted to the engine timing cover and is driven at 2.8 times the engine speed.Vehicles fitted with manual transmission have a one way clutch fitted to the drive pulley, which prevents torsional vibrations from the engine being transmitted to the generator.

The engine control module (ECM) can switch the voltage regulator between two voltages to optimize the charging of the battery.The low voltage regulator setting is 13.6 volts and the high voltage regulator setting is 15.3 volts, measured with the generator at 25°C (77°F) and charging at a rate of 5 amps. These values decrease with a rise in temperature or current flow.

The ECM determines the voltage setting of the voltage regulator. The high voltage setting is always selected by the ECM once the vehicle has started. The ECM determines the period of time that the high voltage setting is selected for.There are three different time periods selected by the ECM which is dependent upon the vehicle conditions when the vehicle is started:

The longest time period is selected if the ECM determines that the vehicle has been 'soaking' for sufficient time to allow the engine coolant temperature (ECT) and the intake air temperature (IAT) to fall within 3°C (37°F) of each other.

The intermediate time period is selected when the ECT and the IAT are below 5°C (41°F).

The shortest time period is the default time and is used to provide a short period of boost charge.

At the end of these time periods the voltage is always set to the low voltage setting to prevent the battery from being overcharged.The time periods are variable depending upon the temperature and the battery voltage.

The target voltage of the battery varies between 14 volts and 15 volts depending upon the ambient temperature and the vehicle operating conditions. Once this target voltage has been achieved, providing the vehicle has been operating for at least the shortest time period, the ECM will reduce the voltage regulator to the minimum setting of 13.6 volts.