Hello I'm new to the forums and a really enter first time jag owner. My battery drains when parked over night but the battery is new. After researching the form I found that I must test each circuit to find what's staying on. I'm confused by the process of doin this and don't understand how.
I am supossed to disconnect the positive battery lea
d, then pull the first fuse and upon reconnecting the lead to the terminal I will see a normal spark if the fuse/circuit is good, and no spark if its bad? I pull fuses 1by1 till there no spark?
Another thing mentioned this process using a ammeter in the circuit to test.
Once I find the correct cuircuit how do I fix it? Do I simply replace the fuse or must I look at the wiring related to that fuse?
If anyone could help me grasp this concept and explain exactly what I need to do I would be more than grateful.
I really like my new jag and hope to be able to fix this problem over the weekend. After a few more minor fixes I will post pictures.

 

Welcome, your stay will be FUN, your vocabulary will EXPAND, and alcohol as a sedative will be your SANITY.

I have been with Jaguar cars since 1968, and NO sign of changing, waaaaaay too much fun.

I am going to assume from your sig that yours is a 1988 XJ-S, V12????.

Take off the +ve (or -ve, my preference) terminal at the battery, connect a digital volt meter between the removed cable and the battery, remaking the circuit. Ensure you have the meter cables plugged into the correct sockets, and the meter set on "amps dc". Most DVM are a 10amp max, so dont try and run "big ticket items, you wont need these "big" items to find a voltage drain.

If the car has an alarm/imobiliser, unplug it.

Measure the draw with the car "sleeping", and it should be about 00.18amps, or lower, and that will be the radio memory, and trip computer clock (if you got one), and that is about all for a "sleeping car".

If you get a lot higher, then something is draining, you know that already, so then the pulling of fuses, one at a time, will give you an idea of what is going on. Once the culprit is found, then ask again, with your findings, and once the circuit at fault is known a fix will be forthcoming.

If you get an acceptable reading, reconnect the alarm/imobiliser, and see what happens. These protection things are a very common cause of flat batteries.

Something else to check. Is the boot (trunk) light going out when you shut the lid, and, if you got one, is the glove compartment light going out when the lid is shut. Much like the light in the fridge, "does it go out when I shut the door"??.

A bad voltage regulator inside the alternator, can go to earth, but that usually is a very large drain, and would flatten the battery very quickly, and the battery lead would give a fairly large spark as it was disconnected.

Enjoy

 

Welcome to the forum 88wasill.

One point to remember, diagnosing is not always easy and is usually by proccess of elimination.

So follow all steps in the chain and the guys will get you going again.

 

Thanks for the help guys.
Yes my car is a 88 xjs v12 i do have the digital trip meeter. My security lift flashes on the radio but for some reason i don't think my alarm works. Also when i open my trunk there is no light that comes on so i haven't even located the bulbs position yet.
My dad has a volt meeter at his house so i will have a chance to work on this this weekend and then post my findings

 

Thanks for the help guys.
Yes my car is a 88 xjs v12 i do have the digital trip meeter. My security lift flashes on the radio but for some reason i don't think my alarm works. Also when i open my trunk there is no light that comes on so i haven't even located the bulbs position yet.
My dad has a volt meeter at his house so i will have a chance to work on this this weekend and then post my findings

 

Welcome 88 you will quickly learn how to fault find. Just remember the golden rule is to do ONE thing at a time.

I had a similar problem and tried measuring the current at the battery with my Dick Smith DVM (a cheapie) and this was not successful battery in the boot (PIA) and nothing would run through the small meter.

Any way my point is: if it does not work what I did was pull ALL of the fuses and use the DVM on current and plug the leads into the connectors where the fuse came from. With everything off you should only have current draw from the radio and trip comp.

DO NOT connect the DVM across the battery terminals while it is in "amps DC mode" this will blow the fuse in the meter.

 

88wasill, I will offer and alternative to what Grant posted above. This process is a lot like his, but can also be a bit more informative. First, obtain a diagram of the fuse box(es) noting what size fuse goes into each slot. If you need to, make your own drawing. Note which spots are blank and what size fuse is used where there are fuses. Now, remove all the fuses for the car. This should remove any drain that you have that is killing the battery. Next, disconnect one of the battery posts and install a multimeter between the battery post and the battery connector. Ensure the lose ends are kept away from any metal parts of the vehicle. ENsure the multimeter is set to the DC amps setting (highest range you have). Note the current at this point. It should be under 0.020 amps. If not, your problem lies in the harness of the car. Now, install the fuses one at a time, checking the multimeter after each fuse. If the multimeter remains under 0.020 amps, install the next fuse. If the meter jumps above 0.020 amps, remove that fuse, make a note of which number fuse it is and then continue on installing all the other fuses. You may have a few fuses that are left out once all is said and done.

Let us know which fuses are left out once you are done and we can figure out what is wrong at that point. Hopefully you will be left with just a single fuse which should make troubleshooting very easy.

 

As already said by me and others, the only add on I had in my head today, this XJC V12 is causing some brain strain, I will win, trust me.

Once the fuses for all the circuits are checked, and IF, and I mean IF you still have issues, it may be a diode inside the alternator that is "leaking" to earth. The alternator is NOT fused, at least on the diode side. To isolate the diodes, remove 1 of the battery cables, reach down to the alternator and undo the nut holding the battery wires to the stud, DONT DROP THAT NUT, remove those wires and INSULATE them (they are LIVE as soon as the battery is connected), and then do your amp test. If nothing changes with this test then the diodes are deemed OK. This failure is NOT common, but at least you can isolate them whilst you are testing the rest of the car.

 

Had a bit to work on the car today. I tested all the fuses under the steering wheel except for three which I couldnt get out. I also tested all the fuses in the two small boxes under the hood. All fuses i tested didn't change the reading. The battery gives a reading of 11.98 on the DVM while the car is "sleeping".
When the car is running i can hear a hissing electrical sound coming from, or under the battery. I also noticed a few wire plug connectings in the trunk hanging and not plugged into anything.
I can post pictures or even upload a video of the trunk noise.

 

I dont think you have quite grasped the concept of the amp draw test.

11.98v is a tad low, so a depleted battery may be all that is causing that, so a charge will retore it to 12.5v as I would expect.

The "electrical hissing:" noise you hear is the fuel pump, it is normal, rest easy, and without that "hiss" you go nowhere.

Take your meter, plug the "black" lead into the "common" socket, plug the "red" lead into the "amps" socket, it is usually seperate from the other socket used to test volts/ohms/etc. Each meter is different, and not knowing what you got I have no idea, but most have 3 sockets to choose from. Now turn the dial to "amps DC" and the highest scale available, usually 10amps. The meter is now set.

You will have to disconnect the earth lead from the battery, now connect the "black" lead of the meter to that battery lead, wrap it in a cloth so it dont short on some metal thing in the boot (trunk, whatever), now connect the "red" lead of the meter to the empty battery terminal. Now read the "amps" on the screen, whatever you see is the "sleeping car draw", NOT the 11.98v that you have reported, that is the battery voltage, important, yes, but NOT what we want to try and find your battery drain.

If the sleeping amps is higher than suggested, you will need to remove the fuse to your stereo system, look again at the screen, what is the number??. If it is still too high, step by step remove fuses one at a time and record what happens to the readings until you get to 0.00amps or real close.

Apart from faults, the only items drawing power whilst sleeping is the stereo memory and the trip computer clock.

Stereos and aftermarket alarms etc are the most common causes of flat batteries in any car, not just Jaguar, so again, IF you got an aftermarket alarm fitted, unplug the power supply, and see what the meter reads. I had one here years ago that was drawing 4amps, and with the alarm unplugged the sleeping car was 0.015amps, which is spot on spec.

 

Hey thanks for sticking with me. I set my meter to the correct settings for sure this time (lol). When I complete the circuit it. initially shows a reading of 0.05 then it drops imediatly to 0.00 and rests. So it apears to be good.

 

So the overnight flat battery is caused by?

 

11.98V is way too low. A car battery is deemed 0% charge when the open terminal voltage (this is with the battery disconnected) is 11.8V.

I would suspect the battery if your quiescent current draw is less than 10mA (0.01A).

Disconnect the battery and measure the terminal voltage if it is lower than 12.6V the battery needs to be charged. The problem might be in the charging circuit of your alternator. It may not be providing the battery with a full charge, if this is the case your battery will go flat very quickly even with a current draw of less than 50mA.

If you have a mains battery charger put the battery on charge over night. In the morning disconnect the battery and measure the voltage it should be over 12.6V. If it is not buy a new battery.

Running a lead acid car battery flat will cause damage to the plates inside and prevent the battery from holding a charge.

If you do not have a charger. Take the car to a battery specialist. They have equipment that can test the battery and your charging circuit.

let us know how you go cheers Warren

 

Yep, with that reading your battery is NOT seeing any draw whilst snoozing, impossible, unless you got no stereo or trip computor, od they are unplugged??.

I reckon you still got issues with the meter, or connection, or scale selected on the meter. If it showa 0.05 and instantly drops to 0.300, then either the scale chosen is too low for what is actually going on and the meter drops to "automatic overload", as some do. Its a protection thing. When you put that meter between the cable and the battery terminal make real sure that the ignition etc is all OFF.

That sudden 0.50 flash tells me you got something serious drawing current, and you will need to make sure the meter is on the correct scale, the leads are in the correct sockets, and IF so, there is something sinister in the car, but until a steady reading is obtained we are all in the dark.

As an example the fuel pump draws 6+amps, the fans inside trhe car draw approx 5+ amps EACH on low, so if anything is switched ON the meter is going to "overload".

A side note to calculate the amps draw, "take the wattage, divide it by the volts used = amps", so a single stop light bulb at 21watt divided by the 12v used = 1.75amps, so it is easy to see how things add up in total over a whole car.

If you are still in the dark/confused, photo your meter showiing the scale you are using, and the sockets the leads are actually plugged into and send them PM to me, and I will assist sorting IF something is astray. Dont take this the wrong way, but if that meter is not connected corectly the readings will be of no use to any of us to try and help solve your issue.

Do not rule out a "bad" battery, it does happen. Dis-connect the battery, take the voltage reading (11.98v you had before), check it again in the morning, next 2-3 days and see if it drops further, it should NOT. Being dis-connected there is nothing draining it, unless it is shorting itself internally as they do.

 

With the battery out of car and a voltage of 11.98 the battery is flat less than 20% charge.

Before you mess around with measuring current I would check the charging. With the battery connected and the engine running you should have at least 13V across the battery.

There is no point in measuring current until you know
1) the car is charging the battery correctly (if the alt is stuffed it could be your prob)
2) you have a good fully charged battery to start with.

 

I tested the battery today its fully charged at 12.7 volts.
As far as the amp test i have taken a picture of my dvm on the settings I am using.
http://www.flickr.com/photos/48164469@N07/4994514286/


Here's a pic of my car
http://www.flickr.com/photos/48164469@N07/4994507300

 

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OK no help with the battery, I'll leave that to the experts.

But the car looks drop dead gorgeous, more pics please.

 

OK, the meter looks fine, the leads etc are correct for amp draw testing.

When you connect it as said previously and get that 0.050, then drop to 0.00, it may be the meter unable to read in "reverse", some do that, dunno why. So reverse the connections. Meaning that if you connected it "red to battery post, and black to battery lead", and the reading above is the result, go the other way "black to battery post and red to battery lead".

You are looking for a constant reading on the meter to try and establish just what amps you car is consuming whilst sleeping.

Just to clarify the charging is getting done correctly, put the "red" lead into the other socket in the meter, and turn the dial to "volts DC 20", and put the meter across the battery, in the car, connected correctly, engine running. You should see 13.8v or thereabouts. If the readings are less than 12.7, the charging circuit is not working, as said before, and the alternator could be your issue, firstly by not charging the battery, and then a possible diode leak to earth, which drains the battery whilst sleeping.

 

Attachment 5101 Our XJ-S, well hers mainly now. Had it for 17 years.

Just looked at you car, SWEET, but NO leaper, whats going on here.