Had not driven the 98 XK8 for 5 days. Started fine but Odometer lights and dash lights were pulsing from dimmer to brighter. Reversed OK but there was a lag in engaging drive, followed by TRANSMISSION FAULT annunciation alternating with STABILITY SYSTEM OFF. ABS warning, check engine lights were on and the Voltmeter was pegged on 17 volts.

Checked the battery connections and the big terminal connections in front of the spare tire. All were tight, as evidenced by the readiness to start, but the ground cable terminal connection was fractured. This was replaced by a new 1 gauge cable, but before doing so, the positive lead was grounded to "reset" the systems. Battery voltage is 12.6 static.

Re-started car and once again pulsing odometer and dash lights although the volt meter was centered at 13 volts throughout with no fluctuation. Engine or transmission also had a pulsing sound. Engaged reverse and the engine smoothed out, engaged drive and the warnings all came back and the voltmeter pegged at 17 volts again even after reverting to Park and my electronic digital voltmeter confirmed 16.99 volts at the battery terminals.

I am hoping that the fundamental problem is the electrical over voltage, which then causes the other systems to shut-down in self-protection and if the over voltage was to be solved, those other problems would not recur.

Any history of symptoms like this and possible cures?

Thanks for all ideas.

Andy

 

Alternator/regulator.

I replaced mine with a Denso rebuilt unit, but be wary of some of the offerings available; there are some recent reports of new faulty:
https://www.jaguarforums.com/forum/x...4/#post1513186

HTH,
Mike

 

Andy, Mike posted my thread from a few months ago. Bottom line - the failing alternator put out enough volts that the battery not charging warning did not display, but not enough to keep her charged. When the battery level reached a low point while driving, all the warnings and dash lights came on.

If you do find it is a falling voltage regulator or alternator, I urge you to find a Denso brand (was OEM).replacement. I had horrible experience with Duralast quality/ performance. Many of us have had similar problems with many other off brand alternators.

Point of reference- I got my rebuilt Denso for $320. While searching for it I came across prices up to $800 for the same unit. None of them were dealer prices.

John

 

You need an alternator! Do not run this car any more till its replaced. 17 volts will damage sensitive electrical components.

 

+1


On reflection, I didn't explain very well.

I had exactly the same symptoms, and found this thread started by Crumble:
https://www.jaguarforums.com/forum/x...90/#post714167

One of the regulator contacts had corroded away, although I opted for a replacement alternator as I didn't want to do the job twice.

John, I linked your thread as a warning on the dubious quality of some rebuilt units, and not that the symptoms were similar. Sorry for the confusion.

Mike

P.S. 'While you're in there' check the bearings on the idler & tensioner pulleys.

 

No problem Mike, it was good advice I agree with you. Unfortunately I didn't listen there first time.

Andy, if you are going to replace the alternator on your 1998, one thing I learned that's not in any of these instructions. The fit for their new alternator is super tight, if I were to install another, I'd have a hole punch (Tool about 3 inches long, working end tapers towards a point) handy to help start and maintain alignment of the front bolt holes for the bottom bolt. You'll see what I mean. John

 

Thanks for the replies and advice, all. The link to Crumble's problem describes precisely what is happening with mine, so as suspected by all, the alternator almost certainly the culprit.

I have to move the car about 15 miles/25 km to be worked on, but do not want to expose anything to 17 volts, so I want to disable the alternator and run on battery alone with reduced loads between here and there. Can anyone indicate if there is a fuse that can be removed to accomplish this and, if so, where it is?

Thanks, all.

Andy

 

Cars operate on the alternator output. The battery is a storage device and enables the starter. Have it towed!

 

Resolved. Alternator replaced and all back to normal, same situation as Crumble!

grantorino: I appreciate your advice but the time, expense and potential risks of a tow outweighed the possible downsides of a short drive on the battery. So I removed the 5A fuse at location 2 in the front left fusebox in the engine compartment to disable the alternator and brought along a spare battery, just in case, but made it fine on the battery alone.

Thanks for all the assistance.

Andy

 

glad it worked out and you are back on the road - have marked this thread as resolved