At times he'd lights are dimmed when turned on. Forcing me to drive with high beams on. After a little while lights go full strength.
Recently while driving radio keeps losing power. At the same time RPM goes wild. Moves up and down, at times even getting stuck at the 7K. Even tho it goes high car does't accelerate. just keeps moving up and down while radio shuts off and turns back on. Eventually on longer rides it all turns normal. Anyone has similar issues? Answers? Please...

 

Other then that the car only has 65K miles on it and drives great. My third XJS since 2000.

 

Have you had your battery tested? It could be something is draining it while it's parked and it is able to be charged once you have the car running. Is it difficult to start?

Also check all grounds, connections to vehicle computers, any wire looms you can get your hands on, etc.

 

I haven't checked the battery. It was on low voltage charger all winter and the car starts normal. Wile radio shutting off and the rpm going haywire car drives and windows operate. I believe could be a grounding issue but I have no idea where to start and locate the computers connections. Any advise? thoughts?

 

Cleaning ALL ground points is a good start. In the boot on the RH side of the battery (you will need to remove the battery for good access) are a lot of ground points. Remove all terminals clean the metal with sandpaper and re-attach the terminals. I used seam sealer over the top to prevent moisture from rusting the bare metal.

There are grounds under the bonnet too, one on the firewall and the main engine ground to the subframe.

 

Disclaimer: Never had the pleasure of an XJS. XJ wuzza 6, in the stable.


The tach is a good clue. As I read your description, the car drives normaly but the tach needle swings wildly, up to 7k at times.


So, the engine is not changing RPM's, only the instrument.


Many tach's are distributor driven. Ignition pulses electronicly changed to move the needle.


So, as the pulse is -, the tach has a + supply.


There fore either or both are being intermittently interrupted.


So, as suggested. start with all system grounds. If the main battery -
is sketchy, other grounds will be sought as trhe juice tries to get home. Odd things happen.


OTH, so much on these cars is related to the ignition switch, that it
can go "wonky". Age and a heavy key ring. Been there. A good switch via David Boger fixed a lot of stuff!!!


Carl

 

So,


1. All grounds sound?
2. Loose ignition switch and or connections?


Carl

 

Thank you for the info. Just removed the battery and it seemed wet on the outside. Looks like it's been leaking thus perhaps not producing an even stream of power? That may explain lack of juice for the dim lights or the surge in juice to effect the rpm/radio fiasco. Which by the way was worse driving in the rain last night. I'll replace the battery after I'm done cleaning the ground wires. Will post the results.
Thanks again

 

Before you go replacing the battery what is the battery voltage (with the battery disconnected)? I don't think your problem will be the battery. It's more likely corroded ground connections, these are high resistance and cause voltage drops, which will give you the symptom you are experiencing.

Also the alternator can cause this if the rectifier is bad, so with the battery connected, start the car and measure the DC voltage should be between 13.8-14.4 volts, next switch your meter to AC volts this should be no more than a couple of miliivolts.

 

Sonny:


Warren is on to it. An over charged battery will vent. The
electrolyte is very corrosive. Dilute sulphuric acid!!! Probably
has messed up the nearby grounds, including the one on the battery.
A meter will read alternator volts output. 13, 14 mebbe low 15's OK.
More, nope. Cooks a battery rather fast.


Carl

 

If you change the battery and nothing improves, whether your test numbers are good or not, it may be time to look at your alternator.

I haven't had this problem with any of my Jags yet, but I did get it consistently on old Mitsubishis: The alternator would test fine at idle and/or when cold, but if you drove the car awhile and let everything get warm, the gremlins would come out. The telltale sign were taillights that would seem to oscillate (bulbs would dim-brighten-dim-brighten over and over) with the headlights on. Kind of funny to watch the car sit in a parking lot and "glow" like that; it made it look alive.

A friend of mine who restores cars for clients on a part-time basis had this happen to his Starion, and he finally changed the alternator just because there was nothing left to try. Problem went away immediately.

But with you finding fluid running down the outside of your battery, that's my pick at this point.

Jess

 

Thank you everyone for the input and ideas shared. It was grounding issues caused by a leaking battery. Although I cleaned the ground cables to the side of the battery, I think the issues were caused by the ground of the positive battery cable itself. As soon as I cleaned it and put a buffer from the trunk metal of the car all troubles went away.
I did replace the battery as well since it was under warranty. All's well that ends well. A big thank you to all of you

Warren is on to it. An over charged battery will vent. The
electrolyte is very corrosive. Dilute sulphuric acid!!! Probably
has messed up the nearby grounds, including the one on the battery.
A meter will read alternator volts output. 13, 14 mebbe low 15's OK.
More, nope. Cooks a battery rather fast.


Carl[/QUOTE]

 

throw away that low voltage charger.... it cooked your battery...
cook Pizza not batteries!

 

You are absolutely correct. It was the battery that caused the issues. It's all fixed

 

My alternator belt broke 2 months ago on the way to school. I had to drive the rest of the way and then back home on the battery only.

Halfway home, stuff started acting weird. With fluctuations power anything remotely sensitive started going haywire. Like people said, check ground and battery, check alternator as well. Does the late XJS show voltage? Last time my alternator died, it was my voltage regulator, but that gave a more consistent stalling.