I have a 2015 toyota corolla with 110k miles. Just only about 2-3 days ago my car started cranking dramatically slower than it usually does. This morning it barely even started. I tested some things with my multimeter and while the car was running the battery read 13.98-14.00 volts. And then i turned the car right back off and while the car was off it read 12.85 volts. It doesnt sound like its the alternator and I dont know how old the battery is because i only bought this car 7 months ago. However there is a good amount of corrosion on the case of the battery. Or perhaps could it be the starter is going bad? Because all the dash lights and interior lights lit up normally before i even started the car this morning. Im confused on whether its the battery, alternator, or starter thats the problem.
Assuming the cables are in good condition and tight the battery is the primary culprit. Have it load tested.
there is a good amount of corrosion on the case of the battery
scrub it off with boiling hot soapy water. Use a wire bristle cup to get the battery posts and cable terminals cleaned up and fresh metal exposed. Tighten them down nicely to get a good connection.
