I have a scan guage connected to my OBD port mounted on my shift console. I use it to monitor voltage and water temp.

Normally the voltage says rock solid after intial start at 13.2 to 13.6 volts no matter what is on idle or at speed.

Today while sitting in the car ideling I noticed the voltage drop to 12.2 and slowly go down a little more, my stock voltage guage also indicated A drop in voltage when I rev'ed the motor the voltage comes back up, dropped again at idle, rev'ed again the voltage returned to normal and stayed there. No additional issues for the rest of the drive.

So what happened? Normally I would say this is a voltage regulator issue but not sure.

What do you folks say? Is my battery warning of a pending issue or my voltage regulator?

 

James, Same thing happened to me a couple of weeks ago. A test over at at Autozone showed battery 100%, starter OK. Votage regulator bad This equals a new alternator.

Please get yours tested to be sure, I hope I am wrong. The truth is, the job is not all that hard. If you do need a new altenator, let us know. I'd like to share cost shopping, brand comparisons and one or two installtion tips.

john

 

Hi James

Sounds like a bad diode on the rectifier plate. You have the choice of replacing the complete alternator or, if bearings and brushes are still ok, just replace the rectifier. See also my earlier post:
https://www.jaguarforums.com/forum/x...ed-car-142785/

good luck,
Chris

 

Chris, thanks for the info and sounds like a good fix. I just have one question?..if you have to buy an alternator anyway to get the parts why not just replace the complete assembly?

Is the alternator that difficult to remove?

Also I took the car for a short run to the market today and wafted starting the volts did not come up as usual, stayed around 12.2 until I rev'ed the engine, then the volts when straight to normal and stayed ther, so something is diffinetly about to break.

 

James, I choose that option for two reasons:
1. for the alternator to come out of an XKR you obviously need to remove belts, to remove belts you need to remove the fan assembly, and to remove the fan assembly the radiator hoses need to come off, and I did not want to mess with the cooling fluid back then.
2. SNG Barrat wants 600$ for an original alternator and 210$ for an aftermarket unit, while the Delco back then sold for less than 100 bucks.

The situation with an XK8 is probably different, and just replacing the alternator is probably the easiest way.

Chris

 

James it's a 2 hour job to take out and install. Taking the fan out is 5 or10 minutes of it.

Hint: get hold of a pair of welders pliers (looks like a channel wrench on steriods) to deal with the hose clamp. This is one where a very frustrating job turns into a 5 second Ez job with right tool.

I strongly recommend getting a rebuilt Denson (OEM brand). I went through 3 Duralast brand alternators in 2 weeks last month.

Getting the alternator out of (or into) the bottom mount is time consuming. Just keep rocking back and forth, it will come out despite how it looks/feels. I did squirt lube there to help get new one in don't know if it helped. Just takes time and patience.

John

 

You also have the option of having your original alternator refurbished (assuming you have other vehicles to drive in the meantime). Based upon the stories I've read here on the forum regarding replacement alternator failures in both the XK8 and S-Type sections, that's what I will do if either of our Jaguar alternators bites the dust....

 

John, Having seen your write up, that's the way I'd go next time as it took me a lot longer than that. You do have the benefit of having done it three times, mind

I also got an exchange rebuilt Denso unit. It was much cheaper (~$200) than a new one.

Sorry for going OT, but, out of curiousity, does your car have the 'suppression module' fitted?

Mike

 

Yes my 1998 does have suppression module. This forced me to remove alt through the front and pull it up parallel to radiator.

You made me smile when you said I have the experience of doing it 3 times. Mike i was surebuilding I'd have the job done in 45min the 3rd time (experience right ?). That was a dream , I wasn't even close ��.

Strangely enough the Duralast had a bottom mount much smaller than the gap you fit into. This made it really ez to insert.

The OEM Denson was same size as the gap. I was scared I wouldn't be ever able to get it to fit. But it's one of those 1um at a time jobs. That felt like it took forever.

For the next guy: once you get it started in this mount, eventually the bottom holes will begin to line up. Insert something smaller diameter than the bolt to help keep the holes aligned and to provide a little leverage. Every little bit helps. I suppose a tapered rod would be great here.

As I type I realize one of my punches would have helped a lot. Truth is I wish I thought of that when I was bent over it doing the job!


John

 

Thanks guys, will try the rebuild route when I get to it. There is a very good starter/alternator rebuild shop on aMaui and the Jag is a hobby car so it can sit as needed.