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Tips
Tips

battery drain

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Sopwith_Camel

Sopwith_Camel

Jedi Knight
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ok my xj x300 drains its batter in hours how do i fine the leak??
steve
 
Remove the positive lead from the battery.
Place a multimeter set on ohms between the positive lead and the earth lead.
Then you can start checking things to see what is pulling the battery down.
Pull fuses one at a time, if the resistance changes dramatically then you will know which circuit the drain is on.
Disconnect the alternator, i have known them to drain a battery in a very short space of time,
In an ideal world the ohms reading should be as close to zero as possible, but on a modern car there will always be something
drawing from the battery.
 
thank you.
yes I replaced the Alternator. and its been back to the shop to check.
 
Other than an electric clock running 24/7? Until you find the problem, put on a battery disconnect. Something like:

disconnect.jpg
 
yes all my MGs have that. but the issue with the XJ is that the battery is in the trunk and the key has a chip that needs electricity
 
Sopwith_Camel said:
yes all my MGs have that. but the issue with the XJ is that the battery is in the trunk and the key has a chip that needs electricity
Click to expand...
Which model xj do you have sopwith, I have the xf and that also needs battery to open the boot, but there is still a key lock also up under the chrome trim. probably need to stand on your head to see it
 
this is a 95 XJ its my one modern.
I have rewired a spridget and a B but they are alot simpler.
 
Be aware that many computerized cars do not shut down completely for up to 45 minutes. If you are measuring draw, keep it in mind, Also some cars do not shut down if the bonnet is open, Us extension leads so you can shut the boot/bonnet.
 
My jag has that but it was left for a month while we were on holiday, started first press when we came back
 
mezy said:
Remove the positive lead from the battery.
Place a multimeter set on ohms between the positive lead and the earth lead.
Then you can start checking things to see what is pulling the battery down.
Pull fuses one at a time, if the resistance changes dramatically then you will know which circuit the drain is on.
Disconnect the alternator, i have known them to drain a battery in a very short space of time,
In an ideal world the ohms reading should be as close to zero as possible, but on a modern car there will always be something
drawing from the battery.
Click to expand...
ok finaly going to try this, dose it have to be the postive lead? do i need the key ON ?
 
hail, so im back in, i have the multimeter on 200 om and its stedy on 1 as i have poped the fuses, half way through.
steve
 
When I have been looking for a drain I do the same test but the meter is set on DCA 200m.
 
ok i will try that i have now pulled each of the Fuses one by one. in the 5 fuse boxes.
do i need to pull the relays?
i could be useing it wrong it is reading 1 with 200 om before i connect it to the battriy. I though i had change on the right front fuse box but it did not replicate.. weather is much better. but i need to finish my grading.
 
What I see wrong from the way I have checked for a drain. #1 meter leads between the battery post and the wire you remove. #2 meter is not set to ohms but to DCA Ma 20m or 200m.
 
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