If your car won’t start but the lights and radio work fine, it could be one of several problems, possibly including a dead battery. The reason why the radio, dash lights, headlights, and other electronics draw power while the engine doesn’t has to do with the amount of current each device draws and what may be interrupting the path.
Check the Battery
Don’t rule out the possibility of a dead battery just because some of the electrical components work. Batteries can sometimes run electronic devices on a low charge. Headlights, radios, and other car electronics draw very little amperage—usually no more than 20 to 30 amps. On the other hand, engine starters pull up to 300 amps all at once, which is too much power for a battery with a low charge.
If the battery tests low with a hydrometer or fails a load test, it must be charged. The problem is solved if it accepts a charge or a jump from another battery and the vehicle starts. It may be a blown fuse, a broken ignition switch, or a bad starter if it doesn’t start.
Check the Fuses, Fusible Links, and Ignition Switch
If the battery is in good shape, check for a blown fuse or fusible link. Check your car’s manual to find the location of the fuse box, then open it. With no power running in the vehicle, inspect the fuse for a metal wire. If the metal wire inside the plastic casing is severed or damaged, a blown fuse is preventing power from reaching the starter relay or solenoid.
You may need a fuse puller to remove the correct fuse and a light source to see its internal components.
If the fuses are in good shape, the car’s ignition switch is faulty. The ignition switch isn’t the mechanical part you put the car key into; it’s the electrical switch that the mechanical part operates. In some situations, the ignition switch delivers power to the car’s electrical components but not the engine starter.
Diagnosing and fixing a broken ignition switch is more complicated than checking for a blown fuse. A good rule of thumb is that if the instrument panel and dashboard do not light up when the key ignition is moved to the second position (between off and on), there may be a problem with the ignition switch.
If you have a manual transmission, a bad clutch pedal position sensor can prevent the engine from turning over while allowing the electronics to work fine. The purpose of the clutch position sensor is to allow the vehicle to start only when the clutch pedal is depressed, so if it fails, the car won’t go anywhere.
Check the Starter
Starter motors sometimes, but not always, make clicking noises when they fail to work. If you turn the key in the ignition and hear a clicking sound, you may have a broken starter. However, sometimes, starters die a silent death. Don’t rule out the starter just because you don’t hear anything.
There are other signs of a broken starter, such as smoke billowing from the engine, a broken solenoid, or oil soak beneath the engine on the starter. To find out for sure, hire a mechanic.
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