Q: Can running the blowers for the AC with the engine off drain the battery?

asked by on

I have gone out to my car on my 45-min lunch break several other times and used the radio and the AC blower fans to move the air in the car and have not had any issues with a dead/weak battery. Today I went out and used the blowers for about 45-min while I did some work on my laptop. It made the battery so weak that the starter motor would turn but not enough to crank the engine. I left the car sit for a few hours and when I left at the end of the day, it started fine. Will running the AC blowers really draw that much battery power to drain it that much? I've done it before with no issues until today. Any thoughts? Thanks!

My car has 11260 miles.
My car has an automatic transmission.

The problem is although the current draw over 45 minutes might be "low", your battery might be weak, meaning it could have a bad cell and a low reserve capacity. It doesn’t take much to "drain" a weak battery. A confusing thing though is your car is only a year or two old thus making a weak (i.e., "old") battery hypothesis, well, weak. Nevertheless, the thing to do is have your battery load tested (any battery shop will do this for free) to determine its actual condition. If it passes the load test (ask for copy of results so you can see the margin by which it passed), it is possible you have excess current draw in your car’s electrical system. Also consider the possibility that during your most recent break, maybe you inadvertently turned the headlights on which would add to the discharge. Get your battery tested, and if it is OK but the starting difficulty returns, a certified technician from YourMechanic, can diagnose your electrical system.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Can running the blowers for the AC with the engine off drain the battery?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: After parked overnight, car loses all electrical power

Hello. This may sound strange, but were you parked under a street light when the battery died? I have experienced faulty florescent lights putting out RF signals (the signals that your remote fob use) that do not let the car...

Q: Steering wheel vibrates

If your steering wheel is vibrating when driving, that could be one of many problems, that may or may not be related to the need for engine mounts. Worn engine mounts will cause vibration, however, worn steering and suspension components,...

Q: My A/C is not blowing cold, 2012 Volkswagen Jetta

There is an easy way to do a type of check by using a low side pressure gauge from a local parts store. Many places sell the can of refrigerant with the hose and gauge that come with it or...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...