1998 Explorer battery not hold charge over few days

Old 04-25-09, 09:14 PM
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1998 Explorer battery not hold charge over few days


I have a 1998 Ford Explorer 4.0 SOHC with 85000 miles. Two month ago (Febuary 2009) I had the first incidence of "vehicle won't start" after a few days of non-usage. I got it jumped and a few days later it happened again. I did not suspect the battery be at fault since I just bought it approx 1 year ago. After charging the battery overnight with a trickle charger, I checked the battery + side and my meter said 12.6V when engine is off and 13.5V when engine is on (same at 13.5V when I rev the engine). I have two other newer Ford vehs and the engine on numbers were both around 14.3V. I therefore theoreticize that my alternator was at fault.

As the weather got warmer 3 wks ago, I pulled out the alternator and brought to Murrays for check and the tester said it was OK. I installed the alternator back and have been driving the vehicle since, although the voltage/battery indicator on the IP often show on the lower side (sometimes close to boarder line). I now think there is some kind of un-intended power drain exist during the none-usage period, and if the period is long enough (e.g. 5 days) the battery would become to weak to start the car.

Can anyone suggest where I should continue my investigation. If possible, give me all potential causes based on my problem description. Thanks.

Old 04-25-09, 09:29 PM
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Easiest DIY method I have seen is this......

Disconnect the Negative cable, sit in the truck, close the doors, and put the keys on the floor. Look and listen, while an assistant "Taps the Battery Cable to the post"......5 seconds on, 5 seconds off, 5 seconds on , 5seconds off. Youre looking for anything that powers up, when the cable is "TAPPED". A piece of cardboard to block sunlight is very helpful, as is a Dark Garage.

Points of interest, Glove box light, Cargo light, Underhood light, Or any other Small Draw Item you can think of. Obviously, Your headlamps would kill the battery in 5 hours, not 5 days, so Adjust you thought process accordingly.
Old 04-26-09, 08:55 AM
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The previous post was an excellent suggestion. Should you strike out - consider pinched wires. I had an 81 Mustang years ago and had a similar problem. I started removing trim components and it turned out the platsic trim around the shifter pinched a wire to ground, just enough to cause a problem.

Good Luck

Dan NJ
Old 04-26-09, 05:18 PM
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As you indicated, it could be an electrical short causing a drain on the battery.

However, the low battery voltage reading on your dash gauge concerns me.

The battery could be defective, even if it's only a year old.

There may be faulty connection(s) e.g. a bad ground. Look for loose connections and corrosion. Corrosion is not always obvious. Sometimes corrosion is a very thin layer that's almost invisible.

If you have replacement battery cables, they may be undersized.
Old 04-27-09, 02:33 PM
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This is a weird and dangerous possible cause. Had an 89 Jeep Cherokee and the positive and negative cables somehow touched each other causing a drain. A more mundane drain may be a power seat being stuck on

Last edited by nightowlpunk; 04-27-09 at 02:35 PM. Reason: New Englandism dropped an R will return it

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