The electrical system of your car has several different voltage and amperage demand systems. The engine starter circuit is designed to carry 12 volts at high current (amperage). This is why a battery cable is larger in diameter compared to other wires in the electrical system. When the ignition key is activated the starter will turn the engine over, if not we have listed below some of the most popular causes for non starter operation.
A. Test Electrical System Voltage. The best way to test for electrical system voltage is use a voltage meter. Attach the voltmeter leads to the positive and negative terminals of the battery. To check a battery surface voltage remove the positive terminal protective cover. Connect the +positive side meter lead (red) to the positive side battery terminal. Connect the - negative (black) side meter lead to the negative battery terminal. With the vehicle not running and the car sitting over night the battery voltage should be between 12.4 and 12.6 volts. To test the system without a volt meter activate the headlights, if they illuminate brightly the electrical system probably has sufficient voltage. If the headlights are dim or not working the battery charge is low or the battery has failed and needs replacing.
Checking Battery Voltage
B. Check Battery Cable Terminals: The starter circuit of your car is a basic electrical circuit and is subject to corrosion and its effects. The first sign that corrosion is effecting the start is when you activate the ignition key to the start position the whole electrical system of the car shuts down. Once the connection has cooled the circuit will reconnect and car electrical will return. Inspect the battery terminals for corrosion but use caution. These deposits are corrosive, and are by-products of a normal battery charge and discharge function. While wearing protective goggles and clothing, use a garden hose to rinse the battery and surrounding area completely. This will dilute the acid to a non-corrosive state. You can also sprinkle baking soda to help neutralize the battery acid. Use a wire brush on the battery terminals to clean thoroughly and reassemble, recheck charging system as needed. If the corrosion is excessive the battery cables will need to be replaced, battery acid migrates down the cable strands and deteriorates the cable internally.
C. Starter Voltage/Amperage Draw Test. Turn the headlights on and observe, then activate the ignition key to crank the engine over. If the headlights stay bright the electrical circuit is not connected, therefore no voltage drop. A popular reason for this is the winding inside the starter has shorted or the starter armature brushes have worn out and replacement is recommended. If headlights dim way down it means your battery is weak and needs either replacement or recharge. As a rule of thumb, a typical car battery will last three to four years before replacement is needed.
D. Check Neutral Safety Switch/Clutch Safety Switch. A neutral or clutch safety switch is used to disengage the electrical circuit from the ignition key to the starter motor as a safety device. Automatic transmission vehicle gear selector needs to be either in park or neutral before the engine will crank. If the gear selector is in any other gear sections the engine will not crank over. A standard transmission vehicle clutch peddle needs to be fully depressed before the engine will crank over. To test this circuit a automotive test light is needed. Attach one end of the test light to engine ground and the other end at the starter trigger terminal of the starter solenoid. The test light should illuminate when the ignition switch is activated (crank engine over). If the test light illuminates the starter motor/solenoid has failed and needs to be replaced. If the test light does not illuminate suspect a neutral safety switch or clutch safety switch. A wiring diagram is needed to trace power from the ignition switch through the safety switch and down to the starter solenoid. Replace failed components as needed and recheck system.
Starter Solenoid (appearance may vary)
E. Testing Anti Theft Device. Some cars have a anti theft system that will not allow the starter to operate. If this system malfunctions the car will not crank over even after the alarm has been disabled. To test this system observe the " security" light on the dash or instrument cluster. If this light flashes while the key is being activated the security system is in failsafe mode. If you have a aftermarket alarm system in your car and you think it may be suspect locate the main system interrupted relay and bypass main control circuit. If car cranks over the alarm system has failed and replacement is needed.
F. Check for Internal Engine Damage. If your engine has had a major malfunction it will not turn over. To check for this condition install a socket wrench on the front crankshaft bolt, then try to rotate. The engine will turn with a certain degree of difficulty but it should rotate a full 360 degrees. If the engine doesn't turn disassembly is required, repair as needed and reassemble.