i am running out of ideas what to do. My problem began when the temperatures began getting hot. I took it to autozone, they said alternator and battery were fine. i talked to the jag dealership that I bought it off of and they said the positive battery cable was a common problem so I changed that. I drive it some more and it still comes on when it gets warm. I then decide to take it back to Autozone when the light is actually on. The guy was bragging about his 4,000 dollar tool and didn't really seem to know what he was doing but he did say it showed that that voltage regular in the alternator had a problem. I then replaced the alternator, just hoping that tool was right. Still not fixed after replacing alternator, so I found on the internet a post of a guy that had been a Jag technician for 12 years and he was talking about checking voltage on cluster so I did that and followed what he said if it was below the amount he stated it could be the negative battery cable or wiring to alternator. I have changed the negative cable now too. The alternator I got is a aftermarket one i purchased through autopartswarehouse and after the alternator has been in, light has been constant, but after replacing negative cable the voltage was in the 13.5 volts or alittle higher. I just don't know what to try, any ideas? If I need to check the wires to the alternator, what do I need to look for? Your help is greatly appreciated. Thanks.

 

Can anyone tell me what this wire is that goes from the battery box to the fuse box?

 

nobody that can help me with either question? I'm missing my Jag.

 

JagMan I was having a problem with the battery light too. I was going on and off. One time i would start the car and no battery light. The next time i started the car battery light. I didn't think much about this as the car worked fine. About a week later my car acted like it had a dying battery, lights and radio worked but didn't have enough juice to crank the car over. I replaced both sets of battery cables with the advice some members here on the forum. I got the cables from Nalley Jaguar, a vendor here on the forum. A friend of mine was a Jaguar mechanic and a friend of the family was a Jaguar mechanic both said that electronic stuff on Jaguars are tempermental. They recommended using all Jaguar parts with anything electronic. With that said you might want to change the aftermarket alternator back to a Jaguar part. The little cable from the battery box to the fuse box, does it have two wire green and green/blue? I'm trying to figure out where it goes. Does it plug into something on the battery box? If so I must not have that piece anymore....

 

yeah bad thing is the one part I do replace with an aftermarket one is the hardest one to change. I do have my old one because I really don't think it was bad. All the cables I got were Jaguar brand but I thought my alternator was bad and jaguar's alternators are a crazy price. I will have to check out that wire in more detail tonight and get back to you. My dad and me just thought it was wierd because all it looks like it goes into is plastic of the battery box.

 

Had the exact same problem, you could even look at my thread which probably isn't too far down.
Mine tuned out to be the battery cables and the battery itself. Cost me $600 but they fixed it in a couple of hours. Heat apparently makes the cables more resistant to electric flow.

 

yeah i am beginning to wonder if its the battery itself, even though it tested out fine the first time I had the car put on a machine after the light came on. I am just trying to get peoples opinions, I appreciate every one that has posted so far.

 

Jagman, do you have access to a multimeter? If so, I have a few checks that you can do to eliminate stuff. doing the checks will be easier if you have either a second person or alligator clip leads. Odds are, you are looking at either bad battery leads or a bad battery, but that is just a guess.

 

that would be great Thermo, I think I can get access to one, if you can let me know what I need to do to test things maybe I can get something figured out and I would be super happy to have my car back. After putting in the new parts I haven't drove it because I would hate to burn up the new parts. My dad and me are the ones working on it so i will have 2 people. Thanks.

 

myjaghasspark, yes it is a blue/green wire that I was talking about. It goes into one of those plastic protective covers from the plastic on the battery box to the front of the fuse box.

 

jagman, first, we are going to do a load test of your battery. This is easier than you think. All you do is you put the red lead of the multimeter (set to VDC) on the battery positive and the black lead on the battery negative. Try to put the probes on the battery lead posts themselves, not stuck into the little gaps of the terminals unless you are 100% sure the posts are not the issue. Now, the battery should read 12.6 VDC (anything less says that the battery is not at 100% charge). Start the car while watching the multimeter. While the engine was cranking, did the voltage drop to below 11.0 VDC? If yes, your battery is on its way out. At this point, disconnect the multimeter, close the hood and take it for a drive to get everything up to temperature. Park the car, open the hood and connect the multimeter with the red lead on the metal part of the engine (any bare metal will work) and put the black lead on the lead post of the battery negative. Start the engine again. Did the multimeter jump above 1 VDC? If yes, you have a bad negative battery cable. Replace the cable. Personally, if you are seeing over 0.5 VDC, that is a sign the cable is starting to go.

Now, move the multimeter over to have the red lead on the battery positive lead post and the black lead on the large terminal of the alternator. Start the car again. Did you see the multimeter jump above 1.0 VDC? If yes, your positive battery cable is bad. Replace (again, the 0.5 VDC difference is what I tend to use, but 1.0 VDC is the standard).

Finally, with the engine running, turn on everything electrical that you can (rear defroster, defroster on high, high beams on, that should be enough). Connect the red lead to the battery positive lead post and the black lead to one of the metal tabs on the top of fuse F27 in the engine bay fuse box (either side, doesn't matter). Do you see more than 1.0 VDC? If yes, your positive battery cable is bad. Replace.

If you have any questions, let me know. All I am really doing is using the starter as a big load. The starter normally pulls around 100 amps, so, any sort of wire problem will show its head.

 

I am going to be unable to run Thermo's tests till probably Saturday but I had a question that might be something to do with it and may not. I have read about other people having this problem but have never seen an answer. After I turn my car off, and have the key out of the ignition, and my headlights aren't turned on, it makes a chiming noise and won't let me lock my doors. It only does this sometimes though and not all the time. Does anyone know anything about this problem? Also how would I be able to find a Jaguar Part Number, I have no idea what the part is. I am trying to figure out what that wire is that "myjaghasspark" and myself are trying to figure out what it is. I have tried most of the numbers on the Jaguar sticker that goes around the protective plastic the wire goes into, but no luck finding out what it is.

 

JagMan, i read on another thread that that wire/connector was used to help keep the battery in great condition while in shipment. It is useless after it has been delivered to the dealer.

 

hmm that is really wierd, doesn't seem like it would do anything, but at least I guess we know now.

 

Thermo, my dad was just curious how those test are any different than the reading you get from the instrument cluster like the voltage. We replaced both negative and positive battery cables but I guess they could have sent me a bad one. They were both Genuine Jaguar cables. Just trying to understand a little better I guess.

 

Jagman, by measuring the "in" and "out" of a cable, you are looking for a high resistance connection or a bad spot in the wire. Like you mentioned, we are simply looking for a problem. Even new items can fail. I am just trying not to "assume". As for the instrument cluster voltage, is it taking the same return path as what you are testing? if you look at the ground cable, it actually has 2 wires coming off of it. One of the ground wires feeds the engine block, the other feeds the body of the car. All the power that your alternator is generating needs to come back to the engine block. So, you are using different wires. Again, I am simply trying to prove something bad.

The other checks that we can do is involving the wiring to the alternator itself and seeing what the computer is doing. This is a little more tricky as you have to access the alternator and past experience has shown that most of the "alternator" problems with the car are actually cable problems.

One thing that I should probably be a little more clear about when doing the cable checks, try to go from the bolt holding the cable to the item to the battery post. That way you are also checking the physical connection of the eye and battery post clamp. Keep in mind that even something as simple as a 0.01 ohm connection resistance can be significant when you are handling 100 amps (can lead to the 1.0 VDC drop). if the resistance is more, the likelihood of getting a bigger voltage drop is even higher. Most multimeters are not capable of measuring that sensitive. Hence why I use a large current to get to something that can be accurately measured.

 

I think I should change the wire from the alternator to the battery cos am still getting the battery flash from time to time and I don't want the cat to die on me. What is the colour of the wire so I can look for it. Again is it an easy thing to do or I need an expert. Do I need to remove the alternator or any other thing in its way to find this wire? Any help pls..

 

I recently replaced my battery cables both positive and negative. The positive cable runs from the battery to the starter and over to the alternator. You can do this yourself. I recommend removing the battery and the battery box so you can get to the starter a bit easier. You will then have to loosen you Air Intake box that is bolted to the manifold. Once you loosen the intake you can raise it out of the way so you can see the positive cable running across the front of the engine. I had to jack my front left end off the ground so I could get under the car and reach the bolt that secures the cable to the altenator. Once you get that hard to reach bolt off that is where i would start replacing the cable. Connect the Altenator, then run the cable across the front of the engine and back to the starter. After connecting the starter back up then run the cable to your battery. Tighten back down the Air intake making sure your snouts connect up to the intake box properly. put the battery box back in, put the battery back in, and reconnect your cables.

 

Thermo, I am not the mechanic but here is what my friend with the volt meter and my dad figured out. We found out that f27 fuse has no power to it. Also the positive cable to fuse box didn't come with the new cable, could this be an issue? I'm hoping this is enough issue to maybe help you out. Please let me know if you have any ideas. Thanks.

 

Jagman, let me look at my diagrams when I get home and I will tell you what to do from there. It may be something very simple as tweaking the connector inside the fuse box. Otherwise it can be something more difficult. I will see what I can come up with and give you some checks to do.