I recently purchased a 1999 XK 8 convertible from California. It has 89000 miles and no rust. I have already dealt with the control module for the stability control and the purge valve replacement. Then the battery and alternator both died. Replaced both and have 14.5 volts at the battery. The gauge reads 14 volts, however the red light on the dash and the gauge are still lit and the error message of battery not charging is coming up. The gry/wht wire from the alternator does not have any power. But even adding power to it does not cancel the red lights. Any ideas as I am stumped.

 

Aftermarket alternators often function properly but unfortunately tend to keep the warning light on the dash illuminated. You are always better off having your factory alternator refurbished. That is what I did more than five years ago. Works for me....

 

Ignore the dash gauge its a computer driven fake gauge.
After 40 years as an auto electrician I have never heard of warning lights problems with after market alternators.
The "ignition warning light " goes between ignition switched live and live on the alternator when it is generating. so 14v each side of the bulb it goes out.
14.5v sounds a little high as they today usually go to about 14.3. as the battery gasses at 14.5v +.
All alternator diode faults show up with warning light abnormalities ,usually they still charge but often dont regulate properly.
I suspect your alternator is faulty ..send it back

 

^^ You apparently have not read the threads on this forum over the years regarding some aftermarket alternators tending to light up the dashboard warning lights even though they are charging properly. It does indeed happen....

 

The regulator needs to be a proper replacement. The rebuilder I trust uses DENSO (Toyota parts) to repair the alternators I take to them.

Some regulators do not 'play nice' with Jaguar electronics.

 

The warning light is run off the diode pack not the regulator

 

However it is derived internally, the 'I'm charging' signal does come from the regulator on the slate/white wire to the IC (4.0L cars). The EG shows it as B+ when active, ground when inactive. I can't decide whether 'active' means the alternator is charging, or that the fault light should be lit.

For the OP, I'd expect the light to extinguish with the slate/white in one state or the other, depending on which way up the logic is.

 

The bulb lights if there is a difference in voltage between the B+ and the warning light wire and goes out when there is 14v on both ends of the bulb. One side of the bulb goes to the main diodes and the other to the Field diodes .
There are alternators where the voltage regulation is done by the ECU but not on our cars which have an internal regulator.
Its not a fault light but an ignition warning light dating from 1900s to tell you you can crank the engine with a handle to start it. With the advent of the alternator it is true that all diode faults show up as a glowing ign warning light dependent on which of the 9 diodes is faulty open or short circuit.
Its faulty take it back.

 

Hello Everyone. Please be patient with me as I try to use the forum. I have an early 1997 Jag XK8 Coupe. I am trying to install a new Alternator. I bought LNC1800AA rebuilt Denso. The new Alternator has three terminals at the plug. My plug which cracked to bits upon removal has ONLY two wires a Green (at top) and a white under it. Then a small harness has a stray Red wire, not connected at all, with a black wire going to the small nut on the Alt. .Can I use this alternator ??? Where can I get a new plug connector? Please help if you can. This job turned UGLY quick. Please HELP if you can. Thanks! Ben

 

This alternator can be used in two wire mode (called Machine sensed) or in 3 wire mode ( called battery sensed) The wire on the nut is battery live and it just goes along to the starter to pick up the battery connection. I have purchased new plugs on ebay or go to an auto electrician in your town to buy one. Search "Denso Alternator plug " it brought up at least 6 at about $10. Its refered to as denso oval. Also fits toyota.
Just wire it up as original in two wire mode.( ford being cheap)