Something draining the battery

[jremington59]

I recently purchased a used 97 explorer with a 5.0. Shorly thereafter I noticed the battery was dying, so I purchased a new one as the other one was outdated.

The last three mornings I have had to use a booster to start it. I fully charged the new one prior to installing it and it reads good. I'm not a wiring guru at all and have no idea how to diagnose the problem.

Can someone help?

 

[marragtop]

Have you tested the alternator? If you do suspect a battery drain, try this:
- take out the hood light bulb and make sure all doors are shut
- unhook the negative battery cable
- using a mutilmeter measure the voltage between the negative terminal and the cable you unhooked
- if the reading is high, start pulling fuses until you find the circuit that is causing the drain.

This will put you closer to determining the problem.

 

[jremington59]

I just got finished running a test light between the neg terminal and the battery post with the terminal off. On fuse 29 not only did the test light go out, but the wrning chime that goes off when you leave the key in or the lights on went off momentarily.

My book says this is the audio system. But with the battery connected there is no radio or lights to the radio.

 

[marragtop]

That could be the fuse that keeps the memory set for your radio stations, so it should have a constant minor draw. Do you have a multimeter so you can quantify the draw?

 

[jremington59]

No I don't. But I may have to buy one.

I noticed last night when I was driving that the radio light and the light at the headliner that displays the temp would occasionaly get bright and then go back to dim.

 

[marragtop]

Did the brightness vary with the engine RPMS? If so, you may have a bad alternator. Have you measured how many volts the alternator is putting out?

 

[jremington59]

The brightness doesn't vary. Just occasionaly with the radio and outside temp lights.

When I put the tester on the battery and pull the fuse for the audio, at first there is a glow and then it goes to nothing.

I was thinking of pulling the radio out and looking at the wiring. Also if I were to leave the fuse out tonight and the battery isn't dead in the morning then that would show it's in that circuit.

Oh, and thanks for the help.

 

[jremington59]

Tonight I went for a ride and watched the clock and the light would go bright and then it would dim again after I hit a bump. When I got home I hit the dash above the radio and the light would get bright and then dim if I kept hitting it so there must be a short somwhere in one of the wires, or in the radio itself.

Why is the radio on the audio fuse when there is a seperate radio fuse?

 

[marragtop]

Are all your dash lights and radio dimming when you hit a bump? If so, the problem could be in the dimmer switch.

 

[jremington59]

The only lights I could see dimming were the radio and the outside temperature display.

I pulled the fuse that I thought was the problem but this morning the battery was dead again. Go figure, lol.

Is there any other tests I can do with just a test light?

 

[jremington59]

I had a friend stop by today and do a couple tests.

He pulled the fuse that powers the memory and the clock and got no voltage reading back to ground. We also tested the alternator and it was putting out over 13 volts.

With no power comong back to ground I haven't a clue where to look from there. The only thing I'm wondering is if the previous owner hooked something up directly and not through the fuse box, but I can't find anything.

Anyone with any other ideas?

 

[jremington59]

There's deffinately a problem. I went and read it again, and with the neg terminal removed I got a reading between the neg terminal and the negative post a reading of 9 volts. I pulled fuses one at a time and none of them pulled dropped the voltage.

 

[marragtop]

9 volts is a big drain and would explain why it's dying overnight. Have your tried pulling fuses from the power distribution box under the hood?

 

[jremington59]

No I haven't. I will do that next.

Can the voltage regulator go bad and cause a draw like that?

 

[jremington59]

I pulled every fuse in the distribution box and the voltage didn't drop.

With all of them checked, wouldn't that mean there has to be a short in something directly related to the positive cable?

 

[robertoa1a]

That test light isn't that useful here. Since the fuse box is in the door jam then the light button in the door needs to be pushed in. If your alternator isn't charging the battery then you are getting all your power from your battery alone.

You need a gadget that measures amp draw. A parts store should be able to let you use one. Milliamps aren't going to cause much of a problem but look for amperage in the .1 or above range. The gadget you use may give you info on a pass fail basis.

 

[robertoa1a]

Do you have an amp or power inverter running all the time? Any after market electronics?

 

[jremington59]

There's no amp in it and I don't think there's any after market electronics.

For the heck of it I put the battery from the other exp that I know is good in this one. I measured the volts and it's 12 so I will let it sit a while and see if it drops. I suppose it's possible to buy a new battery thats no good.... But I'd never be that lucky, lol...

 

[robertoa1a]

I know everyone here is sick of me talking about Harbor Freight tools but they sell a trouble shooting tool. You can view it on the web.

 

[jremington59]

I'm going to check that tool out.

I believe I may have accidently found the problem. My dimmer switch, the one next to the headlights, may be the problem. The dash lights, radio and temp screen go dim and then get bright. I turned the dimmer up, and although the lights got brighter, they didn't seem as bright as the other explorer. I moved the switch side to side and the lights got a lot brighter. But if I turned them down and then up again, they wouldn't get bright until I wiggled and played with the switch, so it's obvious there's a short there.