Shouldn't the starter relay be closed while a car is starting? Why does it open/close frequently when key is turned, making a repeated clicking sound?
Does the relay behave this way only in the low battery case or it clicks always while a car is starting, but clicks are not audible due to the working starter noise?
If the battery is low, the starter solenoid may still receive enough voltage to move its armature against spring tension and close its contacts to send battery current to the starter motor. However, as soon as the starter is energized, the current drain is so great that the voltage at the starter relay falls below the level required for the armature to overcome spring tension, and its contacts open.
As soon as the contacts open, the starter ends its current drain and the voltage at the starter relay returns to a level high enough to move its armature against spring tension and close its contacts to send battery current to the starter motor.
Rinse and repeat, many times per second.
If the battery voltage is too low, the relay may not get enough power to stay closed. Instead, it opens and closes rapidly as it tries to engage, resulting in the clicking sound. The frequent clicking of the starter relay usually indicates insufficient voltage or current from the battery. In a healthy system, the relay should engage smoothly without audible clicks. If you notice this behavior, it’s advisable to check the battery's charge and the condition of the electrical connections.
