Anyone out there ever DIY an alternator replacement on an F-Type? Looks like doing it from underneath the car would be easiest. True? Any other tips?

 

I haven't done it personally, but looking at the service manual it seems easy enough. Attached is a PDF export.
-Disconnect battery
-Remove undertray
-Remove serpentine
-Remove alternator

 

No big deal, but do it on a lift.

 

Thank you.

 

To ensure the correct functioning of the system, have the alternator in the vehicle overhauled by a competent automotive electrical specialist rather than getting one off a shelf at a parts house.

 

What makes you thi k your alternator is bad

 

After driving for an hour or so battery voltage gets low - ~12.2 V. Charging voltage with engine running should be at least 13.5 to 14.5 V. With engine running stays at battery voltage and only briefly jumps into proper charging range every 2 to 5 minutes for about 30 seconds then goes back to battery voltage and keeps falling when I drive.

Note I keep the car on a CTEk all the time. Just put a new battery in the car about two or three months ago.

 

Could be a bad BCM module on the battery too, incorrectly fluctuating the alternator output.

 

I believe that's normal. Nearly all modern cars do this to improve MPG and prolong battery life. The charging is computer controlled. Are you getting a charging system warning?

 

Mine always shows above battery voltage when the engine's running. Sounds like the OP has a fault, either with the alternator or the charging circuitry.

Or could just be a dodgy earth - I had a company car decades ago and after every service the battery went flat after 4 days. I eventually traced it to an earthing strap that was bolted to the fan belt tensioning arm, which the tech managed to break (every time!) when they adjusted the belt tension. D'oh!

 

Did you do a BCM reset after replacing the battery? Mine had very similar symptoms after a battery replacement, but a simple reset fixed it. At the very least I would check for any error codes before starting to replace components.

 

How do you reset the BCM?

 

No charging system warning.

 

I used my iCarsoft LR code reader, but I'm guessing any Jaguar mechanic can also do it for you.