Have a friend turn the key in the ignition to attempt to start the vehicle.
Listen carefully, as you should hear a click when the starter solenoid engages.
If you do not hear a click, the starter solenoid is likely not functioning properly.
If you do hear clicking, the solenoid may be engaging, but not sufficiently.
What is the function of a solenoid in a car?
Its primary function is as the actuating coil of a contactor (a relay designed for large electric currents) which connects the battery to the starter motor proper. All modern cars also use the starter solenoid to move the starter pinion into engagement with the ring gear of the engine.
Can I drive with a bad solenoid?
The short answer is that, yes, you can usually drive a car with a bad shift solenoid. Granted, it might not shift past a particular gear, but you should be able to drive it for a short period of time without causing any serious damage.
What is a solenoid and what is it used for?
Solenoids are most commonly used as electromagnets, and all the examples so far are that kind of solenoid. But there are some other uses. They can be used to slow the flow of electricity in a circuit, making them an example of an inductor, or an impedance device.
Photo in the article by “Picryl”