Skip the auto shop - Our mechanics make house calls

How Long Can I Leave the AC on While My Engine Is Not Running?

AC Parked Car

You’ve parked your car, and are sitting inside waiting. Maybe you’re early for work and don’t want to head into the office just yet. Maybe you’re waiting for your spouse to get done in the convenience store. You don’t want to waste gas, so you turn off the engine, but it’s warm, so you leave the blower running. You know this pulls current from the battery, but just how long can you leave the AC on while your engine isn’t running?

Actually, this is a trick question. You cannot run the AC without the engine running. The air conditioner compressor and clutch are operated by the serpentine belt that runs your other accessories (your alternator, for instance). If the engine isn’t running, then the belt isn’t turning. That means your air conditioner’s not actually on. You cannot use the air conditioner if the engine is not running. It’s as simple as that.

What you’re really doing is running the blower motor. As long as there’s a charge in your battery and you’ve got the key set to the on position (some cars will let you run the blower in the ACC position, too), the blower will continue to operate. However, it’s only blowing air from the outside through the cabin, unless you have recirculate mode active. In that case, it’s just recycling the air in the cabin. It does not actually cool the air. Any sensation of coolness is simply because the air is moving, rather than still.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P0222 OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input
P0222 code definition Throttle/Pedal Position Switch/Sensor B Circuit Low Input What the P0222...
How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...
How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...


Related questions

Q: Does the AC system need to be refilled with refrigerant after the cycling switch is replaced?

A lack of pressure from low refrigerant will absolutely cause a compressor clutch to not engage. If adding refrigerant at home, you make sure to buy a recharge kit that includes a gauge for the system. This is the only...

Q: Rebuilt engine rough idle and wanting to die.

The carburetor may need to be rebuilt or adjusted. The EGR system may also be causing the rough idle due to the EGR partly stuck open. The only way to isolate which one is causing the issue would be to...

Q: AC wont blow on max

Based on the information you provided for your 2010 Dodge Avenger. It is likely that you have a leak in the air conditioning system. You may also have a resistor pack going bad, or the selector switch itself could be...