Hello everyone! I was driving the Jag home today, everything seemed normal until five or so minutes into the drive, here's what happened in order:

The AC flow decreases dramaticlly ( Not all the way off, but close. )
The ABS light comes on.
The ASC/Trac not available messages come on.

This goes on for three seconds or so then all of those lights turn off and the ac goes back to mode I had it on. The same exact problem happened again, three minutes later, and then returned to normal after the three seconds. What is going on here? I also noticed I tried to lock the Jag and nothing would lock, I had to hit the unlock button and then lock again then it worked.

I may be wrong here, but the temp today has been 104 degrees / 40 c and maybe that has something to do with it?

The Jag does have very minor electrical glitches every so often, but nothing like this before. Should I be worried?

Thanks everyone!

- Pilotman

 

You may want to check that your battery voltage is 12.6V or higher. If it is less than 12.6V the ABS/trac messages will come on. Had the same problem last night and I charged up the battery. It went away this morning. If the battery is above 12.6V and you still get the message, then clean the ABS sensors at each wheel. Most likely it is the rear wheel sensor that is the problem and start with those first. All it takes is a piece of metal the size of a staple stuck to the magnetic sensor that will cause the messages. I have to pull out the sensors and clean them once or twice a year.

As to the AC fan, it is a drop in voltage, so check to see if your alternator is charging. Fast way to do that is to disconnect the battery when the engine is running and see if the engine dies. If it does, your alternator or voltage regulator went bad.

Good luck!

 

I do agree that it sounds like something is causing your system voltage to drop.

BUT - although I have done exactly what Piloit recommended for testing the alternator, and in full disclosure I would admit to probably having done so on a Jag, I WOULD NOT RECOMMEND THAT. The voltage coming from an unloaded alternator has spikes upward of 40 volts or more. If you do not believe that, have a look with an oscilloscope. The modules have circuitry to protect themselves from these kind of spikes, but the circuits involve capacitors that degrade over time and remember, the modules are 15 years old or so.

The better poor man's way to see if your alternator is charging is to turn on the high beam headlights and the AC with the engine running and make sure you have a little higher than 12 volts on the battery. An easy way to check system voltage is with your OBD scanner monitoring the voltage parameter. You do have one of them, right?

In the same vein, you should check the battery and engine grounds and the battery cable connections along with the "false bulkhead" connections under the hood.

 

Thanks for the help XJR Pilot and Spark! Today when I drove the Jag home, nothing at all happened. No glitches, nothing. Which makes me wonder if the temp could have been to blame. Should I still test the battery / alternator with a mulitmeter then? If so, I'll go ahead and buy a multimeter and I'll test those asap. Thanks!

- Pilotman

 

Pilotman11-
If you are going to keep an older Jag running, then yes, you need a multimeter. The one at Harbor Freight is less than $10.00 and is plenty accurate. One feature you do want,, though is the ability to test up to 10 amps DC.

A "self healing" failure mode related to heat that matches your symptoms doesn't come to mind.

BTW, you should also have an OBDII scanner to keep one of these beasts on the road. If you use an Android phone, consider a ELM 327 interface ($25.00) and the "Torque" app ($6.95?).

 

Will do, Spark! I was already thinking I probably should buy one, but now I purchased one last night on Amazon, ( Got a good deal on there ) should arrive within 2 days. I'll post what I find out about the batt / alternator with the multimeter here soon. Thanks again.

- Pilotman

 

Keep in mind the cleaning of the ground and power connections. You will need to do this eventually. They seem to cause all sorts of issues and sometimes much aggravation to the uninitiated. ;^)

 

I've also noticed now that the radio seems to reset everytime I start the Jag. When the Jag starts, it's off and not to mention I have to change the frequency back to my news station every time.

About the multimeter testing: I received my multimeter in the mail but today was a little tiring, and by the time I got back home, I didn't have a whole lot of time and sunlight to do the multimeter test; not to mention it looked like it was going to rain and I have no garage. I'll do that tomorrow, if the conditions look stable.

 

Check voltages and if OK at battery then at the radio. If not OK there, then figure where between the two there's a bad connection (often a ground).

 

Well today about to go home from school, the Jag would not start! No clicks, no sounds, nothing. Two minutes later, the system check message came on and the Jag started. Tomorrow I'm taking the Jag to a mechanic shop; on the phone they told me it could be a short, bad connections, alternator, battery. I'll post updates as they come.

 

I predict underhood false bulkhead connection or battery ground strap. But that is just a wild guess!

 

+1 sparkenzap, bad ground or battery. I have attached a great guide for troubleshooting one of our forum members put together. follow it and i am sure you will resolve the isssue

 

Ground strap happened to me. Same type of thing, just dead. Touched the ground post and it was very hot. I had the wife coming with the jumper cables when a wiggle got it to start. It didn't look bad, but the crimp on the braided cable wasn't making a good connection.

 

Thanks everyone for your replies. I got the Jag back from the shop and they found nothing wrong with the Jag. They checked the battery, alternator, everything checked out. Which makes me wonder; where's that ground strap located? The false bulkhead connector seemed fine. Not sure what else.

 

Ground straps are from the negative battery post to the side of the trunk and from the engine to the frame at the right rear of the engine. In my experience, electrical things that fix themselves are soon back to broken!

 

I am convinced that there could be some environmental temperature-related electrical issues on these cars. When I bought mine some years ago, I discovered that first 100 degree day in the summer it would not turn over on the first turn of the key after work, having sat all day in the sunshine and leaving work at the hottest part of the day. I would have to turn the key off and on again before the instrument cluster would even come to life. Never a problem in the morning, in the garage at home or even after driving in the heat. It appeared only after sitting in the sun. After about a month of this, pouring over these forums for an answer and spending many weekends of diagnostics, replacing grounds, etc. to no avail, I thought, "Uh oh, I've bought one of those troublesome Jaguars."

However, figuring it must be temperature related, I put a reflective shade in the windshield, tilted the sunroof and left the windows cracked half an inch. Voila! Following this procedure, its started first time every time for three summers, the old Jag has been very reliable and I've come to love the car. Luckily, we've got secure parking at work even tho its not covered. The downside is if I need to leave my car parked in an unsecured area and will need to start it when the cabin temperature is going to be very hot, then I will drive my Honduh instead. Same thing if its supposed to rain during the day, but then that's what Honduhs are for anyway.

 

In addition to the ground straps on the battery and engine there is also one on the right side between the chassis and body approximately 18 inches or so in the back of the passenger front tire. About halfway between the door and the wheel arch.
It was the one creating my glitches.