For some time now my 96 Disco has been killing a battery in a couple days over a week if I haven't been driving it regularly. I have searched into why it might be doing this, and have tested the battery, and the alternator with a ohm meter, and both checked out as working correctly. I then looked into bad grounds and battery drains, and came across a post on one of the various Discovery forums that said to do a test with a light tester between the negative post on the battery, and the negative cable, and to pull fuses while doing so. When the light goes out then the fault is found. Well I did that and pulled every fuse in the car and nothing changed. It also mentioned to try disconnecting things that didn't have fuses like the alternator, starter, ignition, and instrument console. I went through all of those and still nothing changed and light stayed on. I should mention that the way I tested those was to remove all the wires going to them, except the starter, and that one I just pulled the positive cable off the battery, removed the nut and then just held the small wire that the nut goes on to the positive post on the battery. Then I remembered the large fuses under the hood on the fender wall, and one by one started to remove those, and something happened, but am a bit confused by it. While removing each of the large fuses one by one nothing changed until I got to the W-lift/CDL/Rear Blower fuse, removing it caused the light to dim greatly, and putting it back in caused the light to be bright again. Then I continued and got to the alternator fuse and removed it, and then the light got very dim once again, and I thought ok, so took the previously mentioned W-Lift/etc fuse out thinking it would go out completely, but it just stayed dim. So I am a bit confused as to what might be going on, and hopefully someone might have a slightly better idea. I would appreciate any suggestions as I would really like to get my Disco back on the road now that my back is finally to a point where I can operate the clutch again. I will post the testing procedure below as I know i probably didn't explain it the best.

Method used.
Testing Current Drain

If tests show that the alternator and regulator are operating correctly, but the battery still continually runs down, there may be a short in the electrical system causing a continuous current drain.

To test for the current drain, turn off the ignition switch, the radio, and all lights. Disconnect the clock, if so equipped, by removing its fuse. Turn on the switches for the heated rear window and, if applicable, the air conditioning; this will determine if the load reduction relay is faulty. Disconnect the negative (-) cable from the battery and connect a test light between the cable and the negative post. If the test light comes on, some electrical accessory or a short in the electrical system is draining current from the battery. Isolate the faulty circuit by removing and replacing the fuses one at a time. When the test light goes out, the circuit with the short is located. If no fault is found in this way, a fault may exist in the components without fuses, such as the alternator, the starter motor, the ignition system, and the instrument cluster. Disconnect the items one at a time until the test light goes out.

Low-level current drain may not be detectable with a test light. If the light does not come on, but a current drain is still suspected, repeat the test using an ammeter set to the 0 to 200 mA range.

 

If the alternator fuse feeds the other one, then either one will cause the light to go dim. I would focus on the first fuse that showed results. Maybe leave it off if you can. My '96 battery negative gets disconnected if it is parked for a long time, but can go for a month at least. Water or corrosion on equipment (rear blower motor for example) can cause a path to ground that causes leakage current. The idea of the test is to disconnect power to the offending piece of equipment, then clean it up as time allows.

 

Thanks for the suggestion, I will pull the fuse and give it a test for a couple days to see if it starts to drain. I do know when I got the thing it had a burned out spot on satellite 2 where the fuse for the rear windows as someone tried some rigged wiring and it looks like it burned a bit. The fuse slot was partly melted, and a good deal of the wiring was cooked to bare wire as well. They had rigged up a 10 amp fuse going off the ignition but I pulled the fuse the moment I saw it and never used it. I eventually was able to find and afford a front loom, and ended up pulling the whole dash and everything, and rather than pull the entire loom and replace, I just took the wires I needed and cut, soldered, shrank, and fixed what had been damaged. That was a big job as a lot of other wires got damaged when it cooked, but after that also replaced the window lift ECU as it wasn't working either, but had to fix a couple solder joints on it as they were well, crappy in a couple spots, and if I remember right one or two spots where the legs on the components could wobble/move.

After that it worked fine with no issues, though the windows did work without the key on, and was never sure if that was a normal thing or not, and couldn't ever really find any information about that at the time. Thought I may have accidentally got a solder flow between two points, but couldn't see anything that really stood out to me. Is it possible that could be the issue, as I wouldn't have noticed at the time because it was a daily driver at that point, and for a long time after. It wasn't until I got to have 2 back surgeries in about a year, and then the healing and not being able to really use the clutch even with the spring to make it easier installed. As it would cause my back to get very grouchy, and I didn't want to have a 3rd surgery which also was going to be fusing my spine. So it wasn't until this July when I was really able to get back to using it. Then I ended up having to replace the power steering pump, and the lines to it, and bleed it two different times. Mostly because I forgot to tighten down one of the lines to the steering box to the correct torque and it kinda backed out and drained itself... whoops :P.

Sorry got a little off topic, but recently I got it all good and then discovered the week battery drain, well a week to 8 days or so, but found that and started digging into why, and doing some testing of the grounds under the hood with a multi meter. One thing I am unsure of is if it has rear A/C as it does have AC, but not sure where the rear motor might be, or is that the same motor that runs the fan for the front? As honestly that thing has been a pain since day 1. No matter the heater controls I have used as I bought a second because the first I thought the fan speed control might have been broke, the fan between 3 and 4 doesn't always like to engage, and will only work if you move it back and forth between 3 and 4 and eventually it will click on to 4. Thank you once again, and please let me know what you think on the window ECU part, and the rear blower motor parts, and will check, and update Thursday with if pulling the fuse changed any of the drain.

 

So small update here, went up and decided to start it up and let it run for a bit since it has been quite a while. Sounded noisy as it has been down into the 40s at night, and am running 15w40 Rotella T in it, but odd thing was that the blower motor even though being on 0 kept acting like it was trying to turn itself on, unless I fiddled with the speed control a little then it would stop. It did this a couple times, and not quite sure why, but thought I should mention it. Anyway will update again in a couple days of letting it sit to see if it drains the battery down badly like before. Until then I get to try to figure out where on the steering box it's leaking, since discovered that while it was idling, but at least none of the P/S stuff I replaced leaks so that is good.

 

So it has been a few days since I last went out and started it up, and figured it would be a good day to try. Also doesn't hurt that I remembered I probably should, otherwise might have forgot, but I went up and when I first turned the key to start nothing happened. No click, no nothing. Waited for a second or two and heard some regular interval clicking, and tried again, and it started right up with no weak sounding crank or anything. So I am guessing that the drain is somewhere in the W-Lift/CDL/Rear Blower since I still have the fuse out for that. So could it be possible that when I did the soldering fix I accidentally got a little extra solder/flow between two points, and that is the reason for the windows working with the key off and out of the ignition, and could that be where the battery drain is coming from? Let me know what you all think, and can go from there. Considering both the window lift ECU and blower motor are a pain to remove, hopefully won't have to do both :P. Have a great weekend all, and thank you in advance for any suggestions/thoughts.

 

Good detective work, putting clues together. Definitely check your soldering work, better than 50/50 that's it.

 

I have been thinking it's a bit odd to have the windows work when car was off, but it was kinda cool at the same time. Will go up and pull it out and take a look, probably just got a bit too much somewhere, as I am not bad at soldering, but wouldn't say I am a pro at it.

 

So little bit of a late update, as this weekend was a bit hectic. Took a good look at the window lift ECU, and noticed a couple spots that had been redone, and looked like perhaps a little extra solder got on it. Got those fixed, but thanks to the weekend being hectic, and today being nothing but rain and more rain am unable to get out and test it. Hopefully tomorrow will give me at least a few minutes to test and see.

 

So I dug a bit more into it after checking out the WLift ECU soldering and testing where I had someone better at soldering than me (my Mom) fix the parts that looked iffy. Put the board back in, hooked up power and the windows didn't work. Then I turned the key on and windows all worked as they should, turn key off, and took it out, but windows still worked even with the doors open and no key in ignition. That confused me quite a bit actually as it didn't work when power was first restored, but then went back to working with key off. So I went over and grabbed the one out of my Mom's 95 V8i, and hooked power up once again, it acted the same, worked with all windows with key on. Turn key off and take key out, doors open, and windows don't go down or up with switches, as they shouldn't.

So I got to thinking perhaps something is a bit off on the board I have, so I took them both and compared them. Other than the obvious differences with parts on the board, the two white blocks rather than 4 smaller black ones, and colors and lengths on some of the resistors I honestly couldn't see a huge difference or what it might be. So any help would be greatly appreciated, or if you might not know, perhaps could direct someone or direct me to someone who possibly could. I am at a loss here, and rather confused. Also don't have a part # for the WLift ECU from my mom's as weather didn't permit me to pull the whole group that the WLift ECU is a part of, just allowed me to pull the board out of it's housing. Left pictures big so that details in difference might be easier to spot. Have a great weekend.

Top of WLift ECU from my 96 SD

Bottom of WLift ECU from my 96 SD

Top of WLift ECU from my mom's 95 V8i

Bottom of WLift ECU from my mom's 95 V8i

 

Modern cars have a feature that the windows can be operated after the key is turned off for some time until the timer times out or a door is opened. Maybe the door open feature was added at some point. These design details are always being tweaked. Gives engineers something to do. Maybe see if the windows stop working after some time.