When key is in crank position, solenoid clicks and starter only whirrs indicating to me that starter gear is not engaging flywheel. Battery is 13 months old shows 12.8 volts. Supply to solenoid shows same voltage. Load side of solenoid when key is in the crank position shows 10.6 volts. Voltage at starter when cranking is attempted shows 9.3 volts. Question: Does this indicate that battery is failing under a load or is the starter bad or could it be something else?