5. How to replace the voltage regulator in the 1979-1987 XJ6.
Jaguar Parts Technical Information
From underneath the car, loosen the alternator belt adjuster trunion, remove the belt from the alternator and unbolt the adjuster trunion from the alternator body. Now the alternator can swing away from the engine, allowing you to remove the upper mounting bolt (it's tight, but you can do it). Unplug everything from the back of the alternator, and rotate the alternator so the black plastic cover is pointed toward the ground. You can't pull the alternator out through the bottom of the car, as the sway bar gets in the way, so everything else is done from underneath with the alternator sitting in the car.
Using a nutdriver set, remove the electrical connections and the two small back screws holding the plastic cover on. Take care to remember (or write down) where everything goes back. Remove the black cover and you'll see the regulator. Take it out, replace it with the new part. Assembly is the reverse of disassembly. This will save you an hour or more of work, plus a bunch of frustration with the lower mounting bolts on the A/C compressor (they're a PAIN).
See our Jaguar Parts Store Catalog to order parts.