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

P0121 OBD-II Trouble Code: TPS "A" Circuit Range Performance Problem
P0121 code definition Throttle Pedal Position Sensor/Switch (TPS) A Circuit Range Performance Problem What the P0121 code means P0121 is a generic OBD-II code which indicates that the Engine Control...
Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...
The Traveler’s Guide to Driving in Malaysia
CraigBurrows / Shutterstock.com Malaysia is a popular destination for many tourists today. The country has amazing sights and attractions that you will want to explore....


Related questions

Q: Blower motor works sometimes

Your car has an automatic temperature control system and it sends signals out to the blower controller in the evaporator housing in the engine compartment. The blower controller is the most common failure along with the blower motor. The blower...

Q: Cylinder 2 misfire

You need to pull out the coil and check to see if there is oil in the spark plug hole, or on the plug wire boot. If there is, then replace the valve cover and spark plug boots after cleaning...

Q: How do I use the rear defroster?

The rear defroster gives you added visibility out of the rear window, by defrosting any ice or condensation. To turn on the rear defroster, press the Rear Defroster button.