Based on the symptoms, it sounds like you may have a failing battery or loose, dirty, or corroded electrical connections. Start by measuring the battery voltage with an inexpensive digital voltmeter. If you find near 12.6 volts, move the meter probes from the battery posts to the cable clamps, then measure the voltage while a helper tries to crank the engine. You're looking for the point where the voltage drops significantly, but that drop might only occur when high current is being drawn from the battery, (cranking the engine or even running the power seat).
Wednesday, January 5th, 2011 AT 7:20 AM