ok so first off, hello I am new here my name is Wallace. I drive a 01 s-type 3.0 ok to get this issue started. I got in my car the other day and the gauges all started dropping. while im sitting or driving the will randomly go down to 0 and I mean all gauges. but they also will just back to where they are supposed to be and this is as often as every 10-15 seconds. the battery will eventually drain down to 10v where I will have to charge it. the car acts like it has not elec power as when all the gauges are not working I have no window power and my power steering gets much tougher to use but when the gauges come back on the other things i.e. windows and power steering come back in. the things that I do know are that one the battery tests good and is 100% fully charged when this is happening and that my alternator was replaced yesterday in hopes of fixing this issue with no luck. the battery has 12.8v going to it while car is running which I assume means that the alt is working properly. please help any suggestions! thank you

 

These cars are sensitive to faulty or weak batteries, how old is the battery and I would recommend getting it tested. If it is an OEM unit you can also verify the water levels like the old days. Test voltage while the car is off also

 

If the alternator is working correctly I would be expecting over 14v with the engine on tickover.

 

Voltage of battery is 12.8-12.9 off. Tests good on a battery tester

 

Actuall the alt is putting 13.8 not 12.8 sorry it was a typo

 

The battery is almost 2 years old

 

Faults causing battery drain are reported every now and then. Sometimes it's the key lock on the column, sometimes rear module (RECM) (can be damp in the trunk, remove spare and check), sometimes the light stalk upsetting the GECM, sometimes the wipers not parking properly. And so on.

 

My voltage when running (new alternator also) is right around 13.5V, so I think you're ok.

When you say you lose power steering, that worries me, but also may provide a significant clue. In order for the power steering to work, you accessory belt must be working correctly. With the alternator change, I assume it was still there. But, perhaps the belt is not correct, not correctly routed around the pulleys, or your belt tensioner no longer is holding tension (there is a wear indicator window thingy on the tensioner itself, however, it is tough to see) Intermediate loss of power steering could be from the slipping belt, other items would suffer also such as the alternator (loss of power across the entire care then) and that perhaps is causing your gauges to go also.

Just a theory of mine.

 

The power steering only goes out when the gauges are out. I read the car has something that ups the revs when turning that could be going down with the gauges. There was a good amount of dampness including water in the trunk. I drilled a couple small holes to drain it

 

A drain could easily be due to the dampness. It is very hard to get the trunk fully dried out and even if you do there may be ongoing permanent damage.

You may have a corroded connection (power / ground) so working carefully round those would be worthwhile.

If you're unlucky the RECM or rear fuse box has suffered permanent damage.

The steering looks to be a separate problem unless it is simply that the volts go so low that the PCM just can't figure out to manage to raise the revs.

I'd chase the drain, not the steering.

 

Do u know where the RECM is located?

 

Best to read in JTIS. Proceed with care, though, it's a computer...

Even better - read existing threads about battery drain. They explain at length how to troubleshoot and how hard (sorry) it can be.

 

Thanks to everyone for all your help! I have located and fixed the problem. There's a little black box when ur looking in the trunk that is on the left hand side down by the spare tire. I assume it's for the keyless entry. The wires that go into it come off a harness that has 2 other unused plugs on it. These plugs were dangling down in the bottom of the trunk and were laying in a little puddle of water. U could see on one of them where it had been shorting out. I pulled them out of the puddle dried them n put them up under the paneling in the side of the trunk and all issues are gone. I hope this fix helps someone else when haveing this problem!

 

Excellent.

Can you see writing / numbers on the box so we can try to identify it?

 

The box says XR83-15T850-AA

 

Looks like the Reverse Parking sensor module.

 

now that's a crazy set of symptoms to cure with that particular module. Never saw that coming.

 

I'd say you still have a problem if you're getting water that's creating "puddles" in your trunk. That's just a bad situation all around and will be setting you for other problems down the road.... Best to figure out where that leak is coming from and address it as "puddles in the trunk" is not a design feature on a Jag....

 

^^^ True!

 

Sounds pathomenotic to me!