Q: How do i know if my alternator is bad? The car only clicks but won't start. The horn blows and the light works. I put in a brand

Alternators are tested using a voltmeter while the engine is running. If charging system output measured on the battery posts is around 14.2 to 14.8 volts (see your Service Manual for exact values), that represents normal alternator operation. During one of these incidents of no start, you can hit the starter with a rubber mallet. Sometimes the starter motor armature develops a bad spot and hitting it like that vibrates the armature off of that bad spot and then the starter will work. A more scientific way to diagnose intermittent starter motor operation is to probe for battery voltage at the starter solenoid with the ignition key held in the start position. If there is battery voltage to the solenoid but the starter doesn’t function, the starter should be replaced (subject to confirmation with a few other additional, quick tests). To obtain a resolution of this, and have the required diagnostic steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a no start diagnostic. If indicated by the diagnostic, the starter can be replaced, on a mobile basis, right at your location. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.