Contour Enthusiasts Group Archives Forums General Troubleshooting bad battery?

The past 2 weeks my Motorcraft BXT40 (the closes I can recall) battery has died while I left the car unused for a week. I didn't leave any lights or power accessories on. Both times there was completely no electricity left in the batteries and I needed a jump start. I had my mechanic check it and both alternator and battery measured fine on his meter. This weekend it started up fine but it hasn't been freezing cold as the past two. Only thing I notice was the indicator on the battery went from greenish to redish. Does anyone know what this indicator means?? My warranty just happened to expire 1 month ago.

I would remove the negative cable with the engine off. Put an ammeter between the cable and the negative post to check for current. If there is none, sounds like a bad battery, probably internal short. The red indicator simply tells you the battery is discharged.

Once you measure the amperage draw, a few (1-5) milliamps is normal, as radios normally need a little to keep their memory, but if you measure a draw more than that then you got something on that should not be. Bulbs are typical culprits and draw usually 1/2 to 3 amps, for the small bulbs (you would have noticed the headlamps of course). Suspects include broken bulbs and those bulbs that are hidden like in glovebox, trunk, engine compartment, and others like dome, and other interior lights that are supposed to be out when not in use, the automatic switches not being actuated or are faulty.
The next thing to try is pulling fuses one at a time and rechecking the current draw to locate the circuit the draw is in, if the visual is not working. Draw with drop to normal when found. If draw is under 3 amps start with lighting and stereo circuits, if higher the check the larger draw circuits like heater and big stereo systems
Good luck, may take a few minutes or hours.

Current draw of closer to 160 milliamps seems to be normal..I'd say no more than 200-300 milliamps for sure though.

Brian

One weak cell will foul up the rest of the battery. Simple test, place a voltmeter across the terminals with the engine off. The voltage should be 12.6 or better. If not, you have a cell on the way out and the engine will turn over slower, when it does turn over, or not at all. The worse it becomes, the fewer days between runs it will hold a charge.