Hello i am new to jaguar ownership, and have just brought a 2.7td s type year 2005
It has an intermittent fault . I can drive the car for 200 miles ok, but then just after starting up and maybe doing a mile, the red battery warning light comes on, and will stay on for a mile or two and then go out

When the light is on and the engine running, I get between 13.7 and 13.8 volts at the battery If I check it as soon as the light goes off, I get about 14.20volts
At rest the battery has given anything from 12.45 to 12.8 volts
An obd2 reader has been used and I have no fault codes.
Also on two occasions when the light has come on I have had gearbox fault and the gearbox has locked. Starting the car again clears the gearbox fault.
Once the handbrake warning light also came on saying the handbrake would not engage.
Any ideas on where to start?

 

should say its an auto gearbox

 

Read the codes.

 

The problem is that the obd2 reader shows no codes.
Ran it twice today.
So no codes, but still have an issue???

 

Never heard of one with gearbox fault and no codes. Bad tool?

 

Hmm...

How old is your battery? These cars are notoriously tough on batteries. A marginal one will still let the car start, but will cause some of the faults you are seeing. The red battery light is fairly rare, though, and may be a separate issue.

At the very minimum, I'd charge it overnight on an automatic charger. For charging system troubleshooting, always begin with a fully charged battery. If the battery is more than 5 years old, I wouldn't even mess with it. Just replace it as a precaution to be sure.

After that, see if the red battery light returns. Jaguar has a fairly sophisticated charging system. The alternator puts out a high charging rate at first, and then settles down after a few minutes. I'm not 100% sure, but if the battery is wonky, that could affect the charging operation and cause the red light to illuminate.

The battery light has more to it than a simple low voltage warning found on most vehicles. The circuit for the light is an extension of the voltage regulator module inside the alternator. The module actually has to be healthy enough to say it's not feeling well. In some cases, if the module dies completely, it can't even tell you, so the light stays off as the battery slowly dies. It's kind of a long shot, but it could be the module is intermittently failing, but not able to tell you. Once it does come back to life somewhat, it turns on the light to alert you. The light going away does not necessarily mean all is well, so be careful with that. But before worrying about that too much, I'd get that battery sorted out first and go from there.

Another thing to check is the drive belt tension. If the belt is slipping, that would reduce alternator output and possibly give you the battery light.

Also, be aware the voltage regulator module is a Jaguar-specific part. If you should need to replace the alternator, hang on to the existing one for the time being. Unless you get a genuine Jaguar part, most aftermarket alternators will give you the red light all the time even though they are charging just fine. Some folks have swapped over the module to the new alternator to put out the red light.

 

Thanks. As to the code reader, it says it connects, and works ok on other cars. It picks up the jag, and knows its VIN number etc.
The only thing is that I have tried reading it after the warning lights have gone out.
next time I have warning lights I will try and plug in before they go out.

 

Thats interesting, and falls within my thoughts.
The car is new to me in the last 3 weeks and I have no idea how old the battery is. maybe I should buy a new one and go from there to see if that clears up the problem first.
My worry is that when the battery light comes on, I find that volts to the battery with the engine on are lower than 14v , but every time I check it with the light off I get over 14.2v. Does the module on the alternator regulate voltage to the battery? if so what are its parameters? All other alternators I have checked on other cars either produce over 14.2v or show nothing when they expire.
Do you think it might be a poor earth?
your replies are very useful,

 

The cars have a smart recharge system. The PCM switches the alt's volts when it decides to do so, such as a cold start. Described in the free download workshop manual.

Maybe a (power/ground) poor connection - usually at the battery.

 

Update put in an almost new battery which had been on a rover 75 CDT. also leaned all the earth connections near the battery.
Two days fine, but then this afternoon having parked, turned the car arround, and went 300m and the red battery light came on, and stayed on for about 1km, then went out.
Car drove as normal. Will go and see if any error codes have been stored. Any other ideas.

 

Above should read cleaned not leaned!
Plugged in obd2 reader, got full connection and vin plate of the car, but no stored memory codes. Which helps not at all.
Ideas?

 

A battery drain usually does not set codes - plenty of threads about drains...

 

Thanks for humoring me with another battery. The red battery light could be as simple as a failing alternator. Might even be as simple as worn brushes.

Also, don't forget to check the tension on the drive belt.

Do a good visual inspection on the electrical harness at the alternator, too. With such high output alternators, you sometimes find burnt wires there, especially on the main output wire.

 

So that may explain why before I took out the old battery, it read 12.4 volts with the engine off. However when I took a reading when out of the car i got 12.8v?? Could a drain effect the battery that much by taking out 0.4v with the engine off? It could have been I had the door open?

 

Ok will try putting on my two post left on Monday, and have a look at the alternator. I assume with the undertray off its easy access to the wires?

 

The 12.4 you read with the engine off and door open sounds perfectly normal to me. In addition to the interior lights, the various control modules stay awake for around 45 minutes, if I remember correctly, so that means a light load was present. It also makes sense that it recovered slightly to 12.8 once disconnected.

 

Couldn't tell you about the access.

I went back to reread your first post. You had some other faults, but I'd suggest concentrating on the red battery light first. Those other faults could be a byproduct of a charging problem. If not, they can be revisited at a later date.

It's good you were able to take some voltage readings with the red light on and off. Something is definitely happening there. The most likely culprit is the alternator itself. Not cheap for a unit with the correct Jaguar regulator, so be forewarned. As previously mentioned, I think you can swap over the regulator module so the red light isn't always on like with some aftermarket brands, but I'm not 100% positive on this.

 

Can you use your code reader to check the voltage output of the alternator. If you go to jagrepair.com you can get a copy of the manual.

 

An ordinary OBD tool can give you voltage(s) but not that.

The reported values above look OK as far as the alt. goes, I think.

 

That is why I asked if his can. Mine does let me look at the alternator voltage.