If you've been following my post
https://www.jaguarforums.com/forum/x...me-help-58004/

You would know my battery light went on!
I just got a voltmeter to test my battery and alternator output and here's the results.

Car off = 12.5 volts
Car running = 14.4 volts

Is this correct for the car?
2005 x type 57k miles

 

Harry, yes, this is a "normal" reading for your car. You may find that after the idle drops a little bit, the voltage will fall to 13.7 VDC or so. The computer controls the output of the alternator and it will artificially raise the output of the alternator to put a quick "recovery charge" on the battery to replace the power used to start the car.

As for the output of the alternator, it is a 160 amp alternator in case you were curious.

I have been following your battery light issue and as I said in the post, make the drive home and be happy.

 

What you need to do is monitor voltage on the instrument pack in test mode. Hold the trip button in and start the car. Continue to hold till it goes to "test" the push repeatedlly till it says "batt and the voltage next to it"
now drive the car. The problem with xtype is the cables get old, get hot from the engine and resitance goes up and voltage no longer stays in the 14v range but starts dropping down into the 12's so youre basicaly running on battery power and no longer the alternator.

 

Thank you for helping me with my alternator problem. Today while I was driving around town the battery light went back on. I quickly pulled over and with the car still running I took a reading off my battery with a voltmeter and got 14v.
I then turned the car off and got 12.4v. I started the car again and put it in test mode to read the battery from the dash. With the light still on it bounces around from 13.5 to 13.7v. If these readings are correct then I have no idea why the battery light would go on. The only thing I can think of is that right now the Northeast is in a major heat wave and somehow this is effecting the system. I'm going to call the dealer tommorrow, but I'm afraid of what they are going to tell me! I have no idea how much an alternator in the states can run for this car.
Any thoughts?


p.s. The battery is the original one from 2005. Could the battery itself trigger the light? Or is that just wishful thinking.

 

This really is a easy diag on an xtype. You need new battery cables. Im putting a set on another xtype right now. But that being said voltage in the 13 range is fine. If the car abd battery doesnt need 14v+ its not gonna charge at a uneeded higher rate which just cooks the battery electrolite. Its when it goes down in the 12.6 12.8v or lower range. Another easy test is to take the temps of the battery clamps on the batt terminals. Useally they start running much higher that underhood temps. And this is the issue. They get hot, resistance goes up and they get even hotter and resistance goes even higher. Ive had them get so hot you cannot touch them. I use a infer red temp gun thats about $60 @harbour frieght
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