DIY folks; if your S-Type alternator fails; resist the temptation to buy a $120“rebuilt” from O'Reilly, Napa or AutoZone..........The voltage regulator inthose rebuilt alternators does not interface correctly with the ECM and the chargelight (red battery) comes on.

To resolve this I bought an alternator from a junk yard. I then exchanged the rebuiltalternator’s regulator with the one from the junk yard.......no light.

The other option is to buy an alternator from a Jaguar Dealer.

 

Kinda like this guy it seems:

https://www.jaguarforums.com/forum/s...-ripple-95727/

 

But on the + side, if the li'l red batt light doesn't bother you, no harm is done. Ran an AutoZone alternator on the 03 S-Type 3.0L for 2+ yrs with the constant red Batt light. Since it is the daughter's car and she is some distance away at college, I thought 2 yrs was enough for her to ignore a red warning light, and eventually snagged a replacement from the wrecking yard.
Great idea swapping the regulators. I hid the Autozoner somewhere in the shop...may try the regulator swap if my wrecking yard one plays out.

 

The question here is.... Is the regulator what fails on the original?

Or can it be swapped over as part of the $120 "rebuilt" one. FWIW, most of the box parts store alternators are Ford spec, which doesn't have the interface to the Jag PCM. Hence the problem you are all experiencing.

Take care,

George

 

Another remedy is to have the alternator overhauled by a local automotive electrical shop so the correct parts are used such as the voltage regulator.

 

Sealed for life?

runs ---->