Does anyone know if really oily and dirty ground straps could
cause issues with charging? I found both the 3/4 inch braided ground straps on the driver's side were really oily and dirty,
The car was working fine one evening after I drove it 180 kilometers
then the next day the battery light came on.
I had filled my radiator up and coolant had leaked under the hood, and I was wondering if I could have shorted something out? I found out that the the wrong PSI cap was on the engine coolant fill spot so it was leaking.
i cleaned the ground wires and put in bigger screws to mount the wires on top where the rad is, as the holes were corroded and not making good contact.
I traced on wire from the alternator through the fire wall to a connection in the foot well, and since I had a passenger in the car
I was wondering if a wire got broken in the footwell.
How that is connected is the weirdest thing I have ever seen, is it also grounded in the footwelfootwelln alternator just quit like that?
I did notice that when I start the car up now that it runs alot longer before running the battety down.
Before I did some cleaning of the contacts if the grounding wiress I can run the car for 20 mins before the battery dies, but could only run it 10 mins before the battery went dead.
The alternator is not that old and doesnt have alot of miles on it so I am puzzled as to why it died suddenly.
There is some kind of power draw that kills my battery if I don't remove the cables to the battery, it takes about a week to drain the battery if I didnt start the car every second day before the alternator problem I am having right now.
Which is the best alternator, for this old XJS, the 75 amp, or the 115 amp?
Thanks guys, sorry I have been away so long,been having alot of
health issues related to a herniated disc in my back. It is from an old injury from years ago that finally went south on me.
i will post a pic of the thing connection in the foot well later today, and maybe somebody can help me make sense of it.

 

The XJS Tech Section is probably better than in here, but never mind for now.

YES, grubby/corroded/loose/ whatever, ground straps, wires etc will reek havoc.

YES, the same applies to the Power (+ve) connectors/wires/etc.

I always run a dedicated Battery style earth cable, engine to chassis, and forget that stupid braided stuff.

An alternator can go bad in 10 seconds if earth connectors are crappy, OR, the battery is sulphated up, etc etc.

NOTHING in the footwell to cause this that I have ever seen in any of mine.

You need a plan.

Start with a volt reading, engine running, AT the battery, looking for 14.2 +/-. If you have that, the alternator is basically working.

If NO, then you need to spend a weekend, and dismantle ALL the +ve connectors, paying attention to the battery size connectors IN the engine bay, one each side of the engine, ON the firewall.

Battery cable size connector ON the starter solenoid, with a B+ feed to the alternator, via the steel tube running behind the exhaust manifold.

Earths, alongside the battery, engine (as you know) rad support panel, etc etc, ALL need attention, or you be chasing your tail.

THEN

Is the alternator belt still there??, sounds stupid, its NOT.

MAYBE the alternator needs to come off and be professionally tested, thus eliminating it from the "to do list".

1988, mmmmm, about the time Jaguar started fitting a "Load Dump Module" to the alternator circuit. They go hissy, most owners remove them, and move on, no more silly lights and charging issues. NO idea as all mine were older than that.

Again, there will be heaps more in the XJS Tech Section.

Good luck.