Quite some years ago, the X308 exhibited a weird symptom of the headlights and dash lights brightness varying up and down. I thought it was the alternator, which had already been rebuilt just a couple years earlier, but to test, I bought a cheap <$100 Chinese alternator (looks remarkably identical) off the internet. It was cheap and was going to be a lot faster than taking it back to my alternator/starter shop. Threw on there to see if that would fix it and it didn't. But before I could find the cause of the disease, it went into remission..

Fast forward several years and last night it came back, this time with a vengeance. I always visit my dad on Sunday afternoons (he's 89) and decided to drive the XJ8, having just washed it. I made a stop on the way home but as I left the grocery store, the headlight/dash light dimming/brightening started again, this time interspersed with occasional "Battery not Charging messages". I made it home just fine, backed into the garage, and as I shut off the ignition, the car went completely dead, no interior lights, no power trunk release, nothing. After putting away the groceries, maybe about 15 minutes later, I went back out to the garage and tested the battery voltage at the CTEK connector. Battery is about two years old. Voltage was perfect, but the car was still completely dead. Then as I was removing the trunk floor panels to access and check the battery connections and cables, the car comes back to life. My first thought was that the trunk floor/battery cover section must have touched the positive cable and re-established a loose connection. But no. All the connections were solid, tight and clean as a hospital operating room. All it might have done was to "flex" the cable a little bit.

Now, I'm wondering about the braided aluminum battery cable. I once bought a car at a charity auction that had been donated because it wouldn't start. Ultimately I solved the problem by replacing the positive battery cable. Terminals had been cleaned but the copper strands had green corrosion underneath the insulation sheath 3-4 inches from the terminal end. So, to check the X308's positive cable, I removed it from the car, cut and peeled back some of the insulation to inspect, but it looked clean. I know that aluminum wheels can develop a coat of light oxidation on the surface that's not obvious unless they were originally polished to a mirror-like shine and then just kinda look dull. Question: Can that happen to braided aluminum cables and cause the issues that I'm experiencing? How could you test it? If that's not it, anyone else have the same symptoms and found the solution, before I start chasing electrical ghosts again?

 

Also check the 'power-stud' connection at the false bulkhead in the engine compartment!

 

Like Bob said. I would test wich one is missing when the issue is on. Positive or negative. Braided cables can rot out completely. But they show it outside especially when you wiggle them. Some battery terminals have bad habit to rot inside so it is not visible. That can be difficult to diagnose unless mechanic is touching the the terminal wich is hot hot.

 

I have 6 Jaguars (3 convertibles and 3 sedans) that I drive (in rotation) that all use the H8 battery.(the rest are 'parts-cars')
One car had a NO START/DEAD BATTERY situation every once in a while that I have to grab the POSITIVE cable and 'wiggle' to get the car powered up.
I bought a new battery and moved the batteries in some of my cars.
One day I went to start a car that never had a problem and I had to 'wiggle' the positive cable and the car came to life.
I had an AH HA moment that the battery was the one in the car with the problem prior to moving the batteries around.
It was NOT the car or the cable, it was THE BATTERY.
The fault followed the battery from car-to-car.(must have an internal connection fault?)

 

I've seen what Bob is describing above in motorbike batteries, thankfully not in cars yet as bike batteries are cheaper.

I have also had braided earth leads that look perfectly good but just don't work in the past too, that took a bit of working out as they conduct enough to test voltages everywhere & it was something I'd never thought of after checking it's connections weren't corroded.

 

Jaguars have a lot of electrical connections in the battery power circuit between the battery in the boot and the alternator and starter in the engine bay, and corrosion on some or all of these connections causes cumulative resistance that can cause lots of difficult-to-diagnose electrical gremlins. Cleaning all of these connections is something I've learned to do every few years, or if I'm working on something else near any battery power or ground connection, I'll take a few minutes to disassemble and clean that connection. This can help prevent no start, slow cranking, and other faults such as the notorious Gearbox Fault warnings.

After you clean the false bulkhead post Bob (motorcarman) mentioned, I would recommend removing the engine ground strap and cleaning the terminals, bolts, nuts, washers and mounting points with a small brass-bristle brush and zero-residue electronic contact cleaner (I use the CRC brand).

Next, remove the spare tire and the black plastic cover of the High Power Protection Module, which is mounted low on the bulkhead just right of the vehicle center. Take photos of all the connections so you can reassemble the components correctly. Remove the nuts, detach the cables and remove the megafuses. Clean all the eyelet terminals, threaded studs, washers, nuts and megafuse blades with your brush and contact cleaner, allow to dry, then reassemble.

There are plenty of other connections worth cleaning. You can find all the battery power and ground locations in the Electrical Guide, which you can download at the link below, thanks to Bob, who provided the file, and Gus, who hosts the website:

Jaguar X308 Electrical Guide 2000

See the attached document created by Rob (avt007), which will walk you through many of the common electrical gremlins on the X308.

Also, since your most recent malfunction occurred shortly after washing the car, check for water ingress into the Engine Control Module (ECM, located in the right engine bay compartment near the bulkhead/firewall), and Body Processor Module (BPM) located on the bulkhead/firewall behind the glove box.

Cheers,

Don

 

I remember having a battery issue on the Duchess several years ago. I would charge it up
and in just a few days it would be so depleted there was a "no start" scenario. The battery
tested good and the charging system was adequate but there was a constant draw i could
not seem to find. One night, in total darkness, I noticed a glimmer of light which I discovered
was coming from a partially closed Glove Box door. Since that time (knock on wood) she has
not given me any issue. It just goes to show how "little" things can cause big problems.

 

Yes! That left side latch sometimes does not pop out correctly and a good slam will get the box to stay closed! I've seen that happen on a couple of my cars with attendant battery problems too. Never could find an very effective way to lubricate it.

 

The Battery Bus Protection Module stud connections in the trunk

Never over tighten the battery positive post bolt , splits nut underneith

In theory once the engine started ( with good Alt ) the car will run forever with no battery

 

Didn't seem to be any parasitic drain. When car came back to life on its own, it started up no problem. Only thing I've had time to do so far is visually inspect the already mentioned terminals and nothing is obviously wrong.



Thanks for all the pointers. Will go through the rest of the list of checks probably on Sunday.

 

Late to the thread, but still may be helpful....

Here's directions on checking the braided line (you may find some similarity that I had) and how to rebuild yours... https://www.jaguarforums.com/forum/x...-strap-286910/ ...be sure to scroll all the way down as nilanium posts about using a used X300 strap. But if you want to keep the X308 look and have a new cable, then the rebuild is your friend.

Not knowing how long your car sits, I have said this at least a hundred times on these forums, use a Battery Tender (the brand I use) of your choice if your Jag is going to sit more than 10-14 days. Here's how I setup my tender, go to post #31... https://www.jaguarforums.com/forum/x...-240156/page2/ ...at the beginning of that thread we discuss AGM batteries as well. I see yours is only 2 yrs old, ...future reference is all.

 

I checked for voltage drops across everything like in the troubleshooting guide on Sunday and found none. And of course, the problem has once again resolved itself on its own before I was able to discover a cause. How many years will it last this time or will it reappear in days? Who knows. The only thing I really "did" though in the form of remedy, was during the process of checking, I thoroughly massaged each cable, flexing it this way and that, watching for any fluctuations of the needle, which theoretically could have re-established internal contacts between strands of wire inside each cable. But its probably something else and I'll just have to take my chances and wait for it to fail completely in order to diagnose it.

 

Haven't had a chance to post again till now but finally got it up on the lift last weekend and inspected the braided ground strap from the bellhousing to the body. I had replaced both valve cover gaskets for the umpteenth time a couple of months ago because it was leaking on the driver side. Didn't think at that time to check or clean the ground strap on the passenger side but found it was pretty well soaked in oil. Appeared to be leaking about where the cam position sensor is, running down the back of the engine and bellhousing and right onto the ground strap. Cleaned it with brake cleaner. Replaced the passenger side valve cover gasket again for the bazillionth time plus I threw on a new cam position sensor with a new o-ring just in case that was the actual source of the leak (the tab on the old one broke into little crumbles of plastic while trying to remove it). Don't know if that had anything to do with it or not, but its not out of the realm of possibilities I suppose. I really can't imagine since there's wires and connectors inside the transmission that are constantly submerged in transmission fluid and they aren't affected by oil. At least another leak is fixed (for the moment).

 

Did you detach the ground strap at both ends and clean the terminals, bolts, washers and mounting points? Just cleaning oil that has dripped onto the outside of the mounting bolts won't clean the critical surfaces that electricity passes through...

 

Absolutely. Even hit the contact surfaces with a scotch disk.

 

Hi Phil,

I've just scanned your thread again, and one thought that occurs to me is that an intermittently failing relay could explain your symptoms. Some of the critical relays include the ignition positive relays, EMS control relay, and auxiliary positive relay(s). The Electrical Guide shows their locations. It might be worth swapping some nearby less-important relays in for the critical ones to see if things improve.

In my X308 and X100s I have replaced all these critical relays with new Bosch relays, which seems to have reduced the number of odd electrical gremlins exhibited by each vehicle.

Cheers,

Don

 

Hmmmmmmmmm..... That's an interesting thought. Will have to study on that to figure out which one.

 

Fastest diagnostic approach is to swap all the ones I mentioned with similar relays from nearby in the same fusebox. Off the top of my head, these relays are in two of the engine bay boxes, at least one of the heelboard boxes, and in the trunk box.

 

One of my X308 sedans is affected by this TSB.
Just a heads up and it might have already been addressed?

 

There is 1 secret fuse to generate power with the alternator , takes power to make power ( alternator field winding excitation by way of the powered voltage regulator ) , fuse # 2 / 5 amp Engine Compartment fuse box

For a whole car power distribution test there is one I developed for the similar inline 6 X300 model and your X308 is very similar , this test does not include the path for the alternator to the battery charging / heavy battery cables

The same part # ignition switch provides a ground path to close a " king " relay located in most of the fuse boxes to get power on through to the some but not all fuses ( fuse 10 , 12 , 14 , 16 on all fuse boxes in the X300 case so your X308............ )

With the ignition key in run remove relay Engine Compartment / IG positive then LH Heelboard / IG positive then Engine Management / ECM relay then Trunk / Auxiliary positive relay and you should feel them click in your fingertip back to open

This can be seen on page 93 of your 2000 wiring guide

X300 00/E COVER

This test the IG switch , the relay can be bad / compromised power contacts but still click and there should be a swapping option

The pin 5 is a car frame ground and this connector under the steering column can be contaminated from coffee and such , my pin 5 was green with corrosion , working under the dash can disturb the ground wire / stud

If needed the IG switch can be changed with no new key needed , IG switch removes from key barrel in this pic but not needed for troubleshooting , there is a trick to removing IG switch from car , super wide and not length screwdriver slot