Mysterious battery drain on 98 Trooper...

Hi,
I have a 98 Trooper LTD with about 150 000 KM's on the body and a bit less than 50 000 KM's on the engine. For the last 6 months I have experience an intermittent battery drain when the truck sits for a day or more. I had the battery and alternator checked, no problems there. I bought a new Optima gel cell just to be sure, however, the problem has become persistent. I now have a constant drain when the vehicle sits. Once it's boosted, the battery charges and will restart. It's only after sitting for a while. I have pulled all sorts of fuses..disconnected the radio...even pulled the starter relay fuse over night. Nothing works. Is it possible that my starter is draining the battery by not disengaging, or does anyone have further suggestions? I left the truck sitting for the last 2 days and the battery is competely flat. Not even enough juice to turn on the interior light!
Thanks for any suggestions !!
Dave
Crystal Beach, Ontario, Canada

is it possible? anything is possible, but you'd know if the starter weren't disengaging

this is one of those fun detective jobs that is just a stepbylaborious step job to isolate the problem. don't just pull all sorts of fuses, pull them all and go from there if that solved the problem start putting them back in in groups until you find the area and go from there.

in fact follow your hunch about the starter and disconnect it. in fact, disconnect the negative cable and see what happens overnight.

have you done any testing using VOM?

//bc

I just solve one of these crazy mysterious batter drain problems two weeks ago. Mine was caused by a faulty brake light switch that would come off and on by it self. I found it by happening to see my electric trailer brake controller light was saying my brake switch was on. The crazy thing would turn itself on when the outside temperature dropped below 50 degree F with the car just parked in the barn. I do not know if this is your problem but you might check to see if your brake lights are staying on. Brake lights work even when your car is parked without the key on.

Another thing to look far is anything that has been added to your car by anyone other than the factory. Such as radio, gps, cb, driving lights, electric brake controller,alarm system, trailer light plugs, engine meters, ect.. If you are draining down in 2 days it might be a good idea to dissconnect all the after market stuff and see if the problem goes away.

Remember some cars do catch on fire due to electrical wiring problems.

All good ideas, thanks. I don't think my brake lights are coming on, but I will have a look. I have also been told to use a test light on the battery between the negative cable (disconnected) and the positive still connected. If the light comes on, it will show a short somewhere....thus beginning the task of removing fuses one by one till it goes out. My mechanic used a voltmeter at the battery a few months back and detected a drain. He thought it was my radio, but I have eliminated that completely by removing all audio components. Once I have done the test light, I will post my results. Thanks again.

Dave

Better than a test light is an ammeter. Connected in series at the battery + terminal it will tell you how much current is being drawn from the batt.
50-75 mA is norm, stereo memory, alarm, etc. all draw a little all the time.
If it's high, start pulling fuses. Still high, start disconnecting things.

Had a similar problem once in a Maxima. Current draw around an Amp all fuses disconnected. Disconnected the alt output wire and gone.
One of the diodes in the diode-trio was shorted, charged ok when running, drained batt when off.

Thanks, I'm gonna try the meter when I get back from vacation....the test light revealed nothing. I'll post results.

I noticed that since I changed my transmission out the battery does not seem to pull the same arc that it use to. Being my old transmission had shifting problems and the 4l30e automatic transmission is all electrical it could have be drawing down more current than need be. If you would like to dissconnect the two transmission electrical plugs they are located in front of the air cleaner box. You will have to remove the air cleaner box to get to them. This is easy and can be done in less than a half of an hour. It would seem that the transmission would not have any voltage going to it with the key off but I do not know how the transmission computer functions. Remember these eletrical connector have locking tabs that will need to be pressed in to safely pull them a part. I do not know if it is safe to have the battery hooked up with the transmission computer unplugged. Some computers can be damaged if unplugged with the power on or powered up without a load.

Well...I hooked up the ammeter and found no mystery load. The reading was about 20mA, which makes sense since I have removed the radio. I also disconnected the alternator, but no difference. Now my service engine light is on, so I guess off to the garage it goes. The only other time the service engine light has come on for a real engine issue was when one of my coils went, but at that time the truck wouldn't run. Still mystified. I also pulled every fuse in the truck and it had no effect.......

Well, I hate to admit it, but I was looking too hard. I tore out the Optima battery and threw in my old one....and of course the problem was the battery. Thanks for all your input, if I ever have a real electrical issue, I can repeat these steps. Now, to try and get some money back from Walmart for this dud of a battery............