Can an alternator cause battery drain?
If your battery is not old, but it still drains when the car is off, you should inspect the state of your alternator. A corroded or defective alternator diode will faultily continue charging the circuit even when the car off. This, in turn, will drain your car battery and cause the car not to start.
How long will a car run with a new battery and bad alternator?
In this situation, the battery could last as little as 30 minutes. If you are lucky and could get up to two hours. Note: In case you have to start the car without an alternator, don’t turn off the engine once you’re going. Starting the car flattens the battery down quickly.
Why is my alternator draining my car battery?
Since the alternator isn’t generating vehicle electricity, the problem component pulls from the battery, slowly draining it overnight until your vehicle won’t start.
Why did the battery drain on my new Toyota?
Maybe the voltage drop was from the old battery, if the new one is 12.6 steady for days now. Most auto parts stores and places that sell batteries have a fancy diagnostic machine that will check the battery health and charging system, and they’ll do it for free. You might have a bad new battery; it happens.
When does a car battery start to drain?
If the battery drains when the vehicle sits for three or four days, that’s a lower amp draw than one that drains the battery overnight. Discovering the source of an electrical draw is a process of elimination. First, check the easy stuff.
What should the battery be when the engine is off?
You can’t “refill” what it took to start the car in that amount of time, much less charge it. A good properly charge battery should measure 12.6V with the engine Off, and at least 13.8V when running. Just the fact that a new battery went dead says there is a parasitic draw somewhere. Compressor relays have been known to do this exact thing.