You are describing the typical symptom of a weak battery. While you did not actually say so, it sounds like your mechanic checked the charging system and found it to be working properly. Its job is to recharge the battery after it becomes partially run down from starting the engine, and then to keep the electrical system functioning while you are driving. Sounds like you need a new battery. No point in looking for more elusive causes until you address this really common one.
"Weak" is wide open to interpretation too. The life expectancy of a car battery is five years. If yours is original, it is way past its life expectancy. If it is the car's first replacement battery, you still got its full life out of it.
Bad cable connections at the battery can cause this symptom too, but I am sure your mechanic would have checked for that. Regardless, one important clue is to watch the brightness of the head lights or interior lights when you try to crank the engine. If the battery is weak or has bad connections, the lights will go really dim or off completely when you try to crank the engine. In the less-likely event the lights stay nice and bright, a defective starter solenoid is the better suspect.
Monday, January 4th, 2021 AT 11:22 AM
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