Ann's 96 Dodge Caravan w/the buzzing noise : Show 1318

The car is making a sort of grinding noise on starting. Tom and Ray think it’s the starter motor.

Yes, Tom and Ray are right, it could well be a bad starter motor. But before replacing the starter motor, Ann should ask her mechanic to measure the voltages at the starter motor’s two terminals during cranking. If either of them are lower than 10.5 volts, either due to either an iffy battery, an out of sorts ignition switch, or corroded high resistance wire connections, a buzzing noise can result even though the starter motor is perfectly functional. I’ve experienced this very symptom on my 1970’s Ford truck in fact. Due to a bad battery.

Here’s what happens: Say there’s enough voltage when the key is turned to “start” for the starter selenoid contact to close. So it closes. But when the contacts close, there’s immediately a large current draw to the starter motor, which causes the voltage to drop. Now there isn’t enough voltage to keep the starter selenoid closed, so it opens. Without the large current draw, now the voltage increases enough to again close the starter selenoid. And you see how it goes on an on. The result is an oscillation in the starter selenoid which results in a buzzing noise.