Hello All,

The latest quirk with my '99 XJ8L is that I'm only getting a hair over 12V at the battery when the motor is running. As a result, the battery is slowly running down until the car can't start. It takes a period of weeks, but we eventually get there.

The mechanic tells me that the voltage at the alternator is correct and he suspects some sort of wiring problem, but has no idea where that might be, nor do I.

Could this be a grounding issue somewhere? Is this some sort of common problem that those who've already experienced and fixed it can easily recognize? Any guidance would be appreciated.

Submitted by helicoptorman@… on Mon, 02/24/2014 - 22:39

Hey Guys I have a 1999 vdp and had a sim. problem. I found the coupling under the hood, pass. side in fromt of the compartment box. Covered by a black rubber boot. Their is a copper nut assembly that connects from the batt. to the starter. it actualy is through that plastic wall near the shock tower. When I remover that entire cover ( hood pin latch area ) I found the unseen portion was very corroded . The plastic area was a little melted also. I cleaned it up ,reassembled it , greased it and I got all my voltage back.. It cost me a new batt, alt, and starter first but, I found it in the end. FYI

Submitted by vogelbp@gmail.com on Wed, 12/25/2013 - 15:10

Just to complete the story, based on some recommendations I got on Jaguarforums.com I decided to start a methodical check of connections to/from the battery. It didn't take me long to find the culprit, but I was surprised that the car was always so willing to start given what I found.

The negative cable from the battery to the chassis was not attached quite securely at its ground stud. I am presuming this was taken off when the new battery was installed, but I fail to understand why.

You could see clear evidence of arcing on both sides of the connector where it slides over the stud. I took that cable out, cleaned up both ends and gave them a thin coat of No-Ox-Id A-Special conductive grease and put everything back together. As soon as I started the car and checked voltage at the battery the reading came back as a perfectly normal 14.09V.

I am very glad this fix was as easy as it was and that I decided to start looking for loose connections. I would never in a million years have suspected one to have occurred where I found it, but there it was. Problem solved. [That was a wonderful day-before-Christmas present to myself.]

Submitted by NE98-51693 on Mon, 12/23/2013 - 15:49

Not sure about 99 XJ, but on US cars the alternator should be putting out over 14 volts if the battery is low and trickle down to 12.5 volts or so with a fully charged battery. I would run an alternator test as follows: test battery voltage with the car off and no load, it should be perhaps 12.5 volts. Then start the car and test voltage. record the info, should be between 12.5 and 14.5 volts. Then turn on heater blower and lights all with car running. Voltage should still remain above 12.5 volts but may drop from the prior running car reading. If the alternator is not putting out high enough voltage, I would check the belt and if that looks good, I would replace the alternator. Only other thing to check prior to investing in an alternator is to load test the battery, its a cheaper replacement and easier replacement than the alternator. Is the battery and ground connection clean and good?
RyeJag