Battery keeps losing voltage
Before going to procedure below, lightly rap on all relays with a screwdriver handle, a sticking relay can cause all kinds of problems.
Here is the test procedure for determining battery or alternator problem after requiring a jump start. Note, requires a voltmeter [$3.50 at Harbor Freight]
1] Check battery voltage on non-start vehicle. Will probably be under 12V. Verify good clean connections, look for cracked corroded or loose terminals.
2] Jump start. Note, always have the jumper vehicle running when performing a jump start, sounds basic but I actually had a friend who argued it should not, meaning he would be jumping with less voltage & could strand both vehicles.
3] With jumper cables removed, engine running, check voltage at battery. It should be 12.8V to 13.7V. If below 12.8V the alternator or voltage regulator are suspect. If in the range, the battery is either dead, low on water or in need of a full charge. If over 14.7V the voltage regulator is not functioning properly.
4] Failing those problems, with the vehicle shut off & the doors closed, disconnect the battery ground cable, put a 12V test light between the battery negative & a known good ground. If it lights, something, like an interior or glovebox lamp, is staying on. Remove fuses 1 at a time to find the problem circuit.
May 22, 2012 |
1998 Ford Taurus