a newbie with jag . bad battery drain where to start and what to look for? its a 1989 XJS V-12 32,000 on mileage all and any help iam grateful for.

 

What is indication of drain. How long does it stand. Mine will last 2-3 weeks but then needs a charge. Seems my security system drains it.

 

I use a trickle charger on mine. Same problem, runs flat after a couple of weeks.

 

Batteries last only 3-4 years if the car is not driven much. I always use a battery conditioner tender charger when my vehicles are not driven for a week or more. My batteries tend to last 6 years plus... Sounds like your batteries need replacing.

 

Mine did the same. Drains in time. I installed a battery disconnect switch (marine stye, no spark) and battery hasnt died since.

 

thanks to all battery dis-connect it is . new battery and better tender!!

 

AS nobody has mentioned this to you yet, see if the boot (trunk) light is really turning off when you close the lid. this is the most common cause of drain on our pre facelift cars.

Greg

 

Solve the problem, don't put a band aid on it. Your car is not designed to drain the battery. Take off the negative terminal, put a 12v light between the negative cable and the negative post and push down the trunk light switch. If the light is still lit there is a sizable drain. Pull the trunk light bulbs or rig the switch down and the pull the power antenna lead and see is the light goes out, if it doesn't go in the cab, and pull the fuses one by one till the light goes out. When the light goes out, you've found the culprit. I have a simple tailight bulb and socket with alligator clips on both leads, clip one the the removed negative cable and the other to the post....search away. easy, peazy. Mine was the power antenna shorted.

 

The GF bought me one of these and its one of the most useful pieces of kit I've ever had.

As you can disconnect the battery, while She is in the Garage, or not being used for sometime.

And is also another hurdle for a potential car thief to have to jump over, if you have to leave her parked anywhere.

Rating: 20/10! I wouldn't be without it.

Battery 'Discarnect' Disconnect Switch Isolator Cut-Off Switch+fuselink | eBay

 

I'll be pretty unpopular over this BUT, one, I want my car to work as advertised, no battery drains, it needs to work right and have drain problems fixed. Two, I don't want to have to go in the boot every time I fell like driving and "hook" the battery up and reset the clock etc. Three, I feel sorry for any car thieves out to still an XJS, not exactly on anyones "hit" list.

 

Hi JT

While I agree that the Car should work, without any drain on the battery, if you fit this disconnector, you don't have to turn it off, you can leave it connected in the 'on position' all the time if you want to.

Also this Gadget has a fuseable link, so if you decide to turn the battery off, the clocks will still keep running except this fuse will blow if you try and start her.

You may never need to use it but in my case my Car Alarm/Immobiliser used to drain the battery, so it has been very useful for me, especially during lay up in the Winter.

 

1) I don't turn off battery switch each time I turn off the car. I use it when I dont drive it for a week or two.

2) To test the trunk light. Place cell phone in trunk with video recorder running. Close trunk. Open trunk and watch video.

3) No one wants a battery drain. But these are older cars with crappy wiring and electronics.

 

thanks to all that reply will try and find what the problem is . but a dis-connect with fuse to keep some voltage does peek my thoughts any and all replies are welcomed this is the place and i dont judge anyone i thank you for input ,how you due things make sense to yourself and can help some one like me new to jags

 

My power antenna drain was scary, it smoked a wire running under the console to the boot while I was driving the car and when I found it with the 12v light I was alarmed how hot the unit was. Sorry, I'm personally not going to disguise a problem with a disconnect and chock it up to old and crappy wire ing. When the disconnect is connected you could be asking for trouble. That's why I endorse fixing the problem. I get that there are uses for a disconnect switch for storage etc and one doesn't need to use it everyday. All I'm saying is don't solve the drain problem by using that as the problem may grow into a bigger one when out on the road. Cheers.

 

I agree to find to problems with your battery draw. That is the key. If you have an issue turning off battery is like putting a bandaid on a bullet hole. May stop the blood but doesn't heal he wound. I know how hard that can be with the 5 miles of wire in the car, multiple fuse and relay panels. It can be quite difficult. I'm lucky as I troubleshoot wiring issues as part of my job and find it easier than most.
I use the switch as back up.
If you do buy the disconnect switch make sure it is good qualiy marine application. These dont spark when used. Very important as it sits beside fuel pump, filter, tanks etc.

 

I have been afflicted with the dreaded battery drain problem. Putting an amp meter in series with the battery indicates a 150 mA draw when i make the connection, and it drops to 40 mA after about 10 to 20 seconds. Maybe thats the new fangled radio installed by PO, it's a sudden drop and not like a capacitor charge cycle.

I understand that modern cars have all kinds of electronics and security systems that draw small current, what about our classics? Shouldn't it be zero?

I cant see any lights on in total darkness or hear any fuel pump sounds, so what are some likely culprits so that I can narrow down my drain hunting diagnostics? AC clutch short, antenna, boot light, what else? Probing every single component is going to drive me up the disconnect band aid route, which I'm desperately trying to avoid. Thanks

 

Why not disconnect the radio fuse and then see if the drain stops or not?


Secondly, many anti-theft devices have a drop in current after a X seconds. Have you got one of these fitted?


Greg

 

Your on the right tract; just have to start pulling fuses until the battery drain stops. Then troubleshoot that circuit...Good luck!

 

Will pull the fuses and radio and check as suggested. No security devices on car.

I did more searches and I see that the famed Grant has said that 50ma drain is normal, if thats the case there is something else that may be worth mentioning. Most of the time the car will start fine and hold battery charge even if sitting for a week or two. On rare occasions after i drive somewhere and return to the parking lot after an hour or two, the battery is flat (11 ish volts). If I jump start, all is fine till she wants to embarrass me the next time around.

Can you experts think of likely candidates that would result in this type of intermittent short? The prince of darkness must not win

 

Hi Warlock,


When I was looking at XJS to buy several owners mentioned to me that battery drain after 2 to 3 weeks is fairly common. People mentioned the central locking or leakage through the radio aerial as possible culprits. Not sure if this is correct or not.


I agree with all the posts that the cars should behave as they did when new and we shouldn't have to tinker with the electrics but then in those days most of the cars were probably driven more regularly then they are now.


I have experienced similar intermittent battery issues to you on cars other than jags. I suspect you may have a cell in the battery starting to break down. Might be worth getting someone to check the battery health.


Good luck,
LeeP