My alternator was bad on my 98 xj8 last December, bought new one from online put it in was charging but light remained on dash saying not charging. Original was rebuilt locally and installed still had issues with lights dimming but light on dash was off. Last weekend charging light came back on and voltage steadily dropped to about 10v and back up to just below 13v. Alternator removed again an tested says diode was bad replaced, and bench tested supplying 12v to signal wire tested fine. Reinstalled in car not charging warning light on but. Signal from computer to alternator 5v dc only not 12v as when bench testing. This is my daily driver and this is the 5th time the alternator has been removed. Any help and guidance is much appreciated.

 

I feel you pain ....Getting the OE rebuilt is normally a very good route ... sounds like it was not properly rebuilt.

Still better vs the units from the big parts places -- I have had them bad out of the box as you.

 

Go to a salvage yard and get a used Alternator. If you think it might need refreshing, take it to a good local starter/alternator repair shop.

I have a REALLY good shop near me and I take the ALT/STARTER to them for repair.
Auto Parts Stores seem to be the worst places for ALT/STARTER replacements.

Many get the units from Mexico or other cheap sources. Sometimes you win, Sometimes???????????????????????????????

bob

 

The problem with anything other than a self or local rebuild is
that the Jaguar alternator of that vintage uses a fairly unique
regulator. Only two pins of the plug are live.

These regulators are not exactly easy to find.

This means what comes in the box may have the right pulley
and be clocked correctly ... but wrong regulator. That's when
the alternator warning light stays on.

 

I bought a brand new denso unit for less than the spare parts... I think it was €155...

Part number is: DAN672

The charge light turns off and I've had no problems since fitting it in February...

 

Denso reman 210-0421 $174 on Amazon. That's the way to go.

 

In the cars current state the not charging light is out but the alternator is not charging at all. I have another alternator on its way but mechanic thinks it is because of the only having 5v signal coming from the computer instead of 12v.

 

That does look to be the OE unit rebuilt at a Denso facility .... that's a fantastic price ... the way to go.

Most of what is available are clones ... or OE units that have been rebuilt with aftermarket parts. They are not really rebuilt .. more like fixed. And not by Denso.


Years ago parts got remanufactured -- now they are checked and fixed .. sent back out with a warranty. Getting one done from Denso is going be of the highest available today with the correct parts -- it still may not have new bearings.


My local guy (rebuilder) -- who was great ....died. His son was just not able to make it work -- they closed. With greater reliability -- and the cheap replacements .. the amount of work available has declined. He did a lot of pool pumps -- people would rather get cheap motors from China vs get the better ones rebuilt for about the same price.

 

With Bob on this: most cities have a couple of guys who rebuild and install alternators and starters as their sole line of business. Rebuild and reinstall for around $200 and they have every known plug and bench test the unit before installing. Did mine in January this year, job finished before my wife and and I could get home in her car. It is that easy when that is what you do for a living. Maybe half the alternators on the road, today, are Denso!