One of the most important parts of the car starter mechanism, is the solenoid, without which, the whole system is useless. It is the important link that connects a car battery with the starter motor. It can be a very frustrating experience when your car refuses to start and you are in a hurry to leave. That is why, it is important that you know how to diagnose and deal with car starter problems.
What is a Starter Solenoid?
As you turn the ignition key, a car's starter motor is switched on, by power delivered by the battery, via the solenoid. It is a relay that closes metal contacts with the starter motor, when it receives a current from the car battery and ignition switch. As a result of the current being delivered, the motor starts working. This makes a retractable rotating gear engage with the flywheel and turn it to crank the engine. Thus, the starter solenoid provides power to drive the motor.
So, when your car doesn't start, it may be due to the malfunctioning of several parts that come into play, ranging from the car battery to the retractable gear. There are two main types of starter solenoids. One type only acts as a switch, which closes the circuit between battery and motor. The other type may act as a switch, as well as move the plunger, that engages the gear with the flywheel. Insufficient power, delivered from the car battery, can be the reason for a starter solenoid not being able to switch on the motor.
As I said before, if your car is not starting, there could be many defects in the entire link, that you will need to check, before you can narrow down to the starter solenoid as the culprit. You need to know the various symptoms of a bad starter, to diagnose the problem accurately.
Put the car in neutral gear and let the parking brake be on. The first link in the chain is the battery. You need to check the battery and ensure that it is in a good working condition, before you go ahead. Arm yourself with a voltmeter and check whether the battery output voltage is around 12 V. If it is, then you can proceed with the rest of starter solenoid testing procedure.
Next car part, that could be the culprit for a starter system not working, is the ignition switch. Refer car manual to test the ignition switch and see to it that it is in perfect working condition. If the ignition switch is alright, then the problem could be with starter motor itself. To check that possibility, refer car manual and directly connect the battery with starter motor, to test working. If the motor's working fine, then test the solenoid.
Locate the starter solenoid and refer to its circuit, provided in a car manual. Disconnect the wire, that runs from ignition switch to the solenoid. In order to test the solenoid, use insulated pliers or a screwdriver to short the big post on it, with the ignition switch terminal on the same device. This will directly transfer power to the solenoid, without the ignition switch current. Now, ask somebody to switch on the ignition.
If your engine cranks, with the ignition switch terminal shorted in this way, then your solenoid is in good working condition and the problem is elsewhere. Otherwise, if the engine doesn't crank, you'll have to replace the solenoid. In case, you are not confident about pulling off this procedure, take help from a car mechanic.
For more detailed guidelines on starter troubleshooting, I suggest that you buy the appropriate Hayne's manual for your car model. It will have detailed instructions regarding the testing procedures.