Electrical faults are a wonderful thing to keep you busy. Here's my story about my S Type model 2000, 3.0.

Car has a substantial power drain. Battery goes flat in a couple of days. First reading was 4 amps. Rear roof lights didn't dim out when car was locked, and there's an issue with the light switch, so I pulled the related fuse in the rear distribution box. I see this as a small issue, and not the main electrical fault.

So I started pulling fuse by fuse in the car and found #20 located in the passenger footwell fusebox is the cause of the drain. Also the four switched relays in the rear power distribution box, located in the trunk draws current, about 1-2 Amps.

To add to the story is I did have the trunk lid open, without securing the trunk open latch in the inner most position. And as I was pulling fuses from the passenger footwell box, the driver's door was open.

Could anyone point me in a direction? Is there a common current draw issue related to fuse #20? Where do I start?

I found a service bulleting detailing a cable cause battery drain between the front passenger footwell and main junction box. That would be one place to start for me.

My S Type will kill a battery in 2-3 days. I installed a battery

Would be happy for any inputs, since electrical faults finding is a time consuming process, starting from the level of no previous experience on the specific model.

Background info:
There is an issue with the heating, I can only get heating and no cold air, same for both sides. So I've read it can relate to the AC control circuit (I don't have navigation) being burned by a defective heater valve. So wonder if that is common to cause a battery drain?

Also the previous owner had installed say 20 LED ramps all over the car, front, back, inside. Have removed all I have found so far. Remains is some connection inside the car. Sure, those are hot candidates to be parasitic drawing, but would prefer to start with standard current draw issues. I have a whole bag of cables. The previous owner mixed soldering, matching small and big leads together, connecting to tail lights, installing lights in the windshield washers, you name it, was a rolling christmas tree once.

Thanks!

//Daniel

 

I think you should re-test but with the various door/etc switches fooled (or doors etc shut), and refer to the Electrical Guide - free download in workshop manual. It also has detailed help for testing.

Be sure to read about what happens before things shut down (i.e. they take time) and you're looking for a final value well under 100mA.

 

Thanks JagV8 for your reply. I have a feeling the service bulletin-related issue is what is going on with my car, but you can never know for sure.

Testing the drain again would narrow things down a bit, I feel confident the culprit circuit is still related to fuse 20 in the passenger footwell fuse box.

I'll keep you posted. Perhaps I get time to look at it tomorrow after work.

 

Hi Daniel,
Those things are surely like looking for the needle in the haystack. Search out Brutal's posts on the ignition switch leading to battery drain.

Did the heat issue precede all of your fuse-pulling? It takes electrical power to close the heater valve, so if you have pulled a fuse that powers the valve, you will have heat regardless of what the control is trying to do with it.