I have to remove the positive cable off the battery when it’s not running or it will drain and ruin my battery.
Then I must replace the positive cable when I want to drive my 2001 XK8 drop top.
Any ideas on what would cause this to happen gentlemen?

 

Hang on for a mod to move post to correct forum (or re-post there).

Or hunt for posts about a current (or power) drain.

 

I've moved your post from General Tech Help to XK8/XKR forum. This is the place to post questions about your model.

Graham

 

Hi Michelle,

This is good, a focused question about a single issue, let's help you out. As I recall you are finding that your battery drains if you don't disconnect the positive cable.

This means something in the car is not shutting off when you remove the key, it is drawing current. Just in case you didn't know, current is measured in amperes, we always shorten the term and call it amps.

Its pretty easy to track down, but unless you're experiencing the key gate issue (described below), I don't know how you can proceed without using a DMM, or digital multi meter. If you don't have one yet, IMO you will have to beg, borrow, or buy one. You can get a perfectly decent one for this job for about $10 in radio Shack. It must be able to measure amps, the one I described does.

Now any XK8 will use a tiny amount of current when turned off, keeps the clock going, radio memory, etc.. as I recall that's about .030 amps.

Normally I would suggest the 1st step be to put the DMM (guess you could call it am ammeter in this case since you're measuring amps) in between the positive cable and battery positive terminal (IOW, one probe on the cable, one probe on the battery terminal). This would force any electricity that the car uses through the meter. But, since you know there is a drain, all this would tell you is how much "extra" current is being used.

Let's do the easiest test first. Look at the slot your ignition key goes into. When the key is removed, a gate that almost covers the opening should spring down. This gate action tells the car that the key is removed, start shutting circuits down. If the gate gets stuck up, it will drain the battery. Take a look and see.

If that's ok: Next we have to figure what circuit is drawing current on you. There are 2 ways to do this. See which you like best.

OPTION 1

1) set your meter to amps (you're going to have to put one of the probe's plug on the meter into a different hole than when you measure voltage or resistance).

2) open the first fuse box. Pull out the first fuse. Put one of the probes into each of the two spring contacts that was holding the fuse.

3) read the amps in the display.

Remember, the car uses .3 amps normally, we are looking for something above that.

4) replace the fuse, move to the next fuse.

Eventually you will find a circuit that's drawing more current than it should.

OPTION 2

The inside of each fuse will actually change resistance depending on how much current it is passing. You can actually infer current by measuring voltage drop across a fuse.

Battery must read at least 12.6 volts.
Look at one of the fuses. On top where it lists the number of amps, look and see that there is a slot cut through the plastic just above each leg of the fuse. This allows you to place a probe in and measure without removing the fuse.
You will be sure the probes are plugged into the meters holes for ground and volts / ohms.
Set the meter to milli volts.
The millivolts reading across the fuse will tell you how much current is being drawn. Different color fuses have different results, there is a chart in the video below.

This video explains it best:

Michelle, I'd vote for the 2nd option, but use whichever feels best for you. Once you determine the circuit that's guilty post here and we will help you get to the bottom of which component is guilty.

Don't forget, as soon as you determine the circuit, you can just pull the fuse and leave the battery connected.

Hope this helps,

John

 

Michelle, I forgot to mention something. You'll see this in the video, but your going to have to fool the car into thinking the door is shut or lights will draw current. Take a big screwdriver and force the striker into closed position for the door you have to open to get to the fuse box. Just pull on the inside handle to reset the strike when you're done AND BEFORE you close that door.

J

 

Michelle,

Sorry to hear about your “ blues” but it’s fixable.

+1 to John’s detailed method above to find the source.

I would do a visual/ear/feel check first as you may be able to find the drain. Could be a number, and/or a combination, of things. A common fault is under the centre console arm rest. If someone has added modifications like a blue tooth receiver or chargers they may have used a wrong permanent power on supply instead of an ignition controlled power supply for the mod.

Check the keyhole behind the steering wheel, as John suggested. Lock yourself in the car and check around. Has the overhead console reading lights turned off? Are the exterior lights on - the rear lights are known to have an electrical fault develop so are they on all the time. Are there any noises still present, listening from the driver’s seat ie heater/AC fans, whirring behind, hissing/buzzing? Could be the radio deck? Is it original or upgraded?

When you turn the key to on, but don’t start the engine, listen to the noises. You should hear the pump on the fuel tank turn on, and relays clicking, airbags charging up etc. One of these could be on all the time.

With the car dead, do the same in the trunk. Remove the right carpet liner to check the rack. This includes the hydraulic pump for the convertible top. Another forum member Ryan B noted his music power amp, here, was on all the time as he could hear the fan inside and the unit was hot.

Good luck and let us know what you find.