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

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.


Next Step

Schedule Electric Problems Inspection

The most popular service booked by readers of this article is Electric Problems Inspection. Once the problem has been diagnosed, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. YourMechanic’s technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews... LEARN MORE

SEE PRICING & SCHEDULING

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

Recent Electric Problems Inspection reviews

Excellent Rating

(653)

Rating Summary
607
17
7
5
17
607
17
7
5
17

Nicholas

11 years of experience
516 reviews
Nicholas
11 years of experience
Jeep Wrangler V6-3.6L - Electric Problems - Apex, North Carolina
Nicholas always provides trustworthy and highly professional service. I would go with yourmechanic everytime if I get a mechanic like him.
Mazda CX-9 - Electric Problems - Morrisville, North Carolina
Super convenient. Mechanic showed up right on time. Fortunately, our issue was easily resolved with minimal hassle.

JOHNNY

33 years of experience
170 reviews
JOHNNY
33 years of experience
Ford Edge V6-3.5L - Electric Problems - Citrus Heights, California
Johnny was on time, honest, professional and very informative. Best experience that I've had in regards to mechanical work.
Honda Accord - Electric Problems - Roseville, California
Johnny was great he saved my family money very nice very respectful one of the best mechanic I have ever met and seen I will pick him for all future needs

Gustavo

17 years of experience
336 reviews
Gustavo
17 years of experience
Jeep Wrangler V6-3.6L - Electric Problems - Converse, Texas
The men knows his stuff! Glad to get someone with Jeep experience. He figured out the real problem and got my girl on the road again! Will definitely request him again.

Andre

16 years of experience
37 reviews
Andre
16 years of experience
Ford Tempo L4-2.3L - Electric Problems - Gambrills, Maryland
Andres was friendly, professional and competent. He methodically diagnosed the electrical problem - the seat adjustment connection was stuck in the on position - and he was happy when he did so. I asked him many questions and he was supportive and knowledgeable. What a great service .

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

Related articles

Do All A/C Systems Use Refrigerant?
All air conditioning systems use refrigerant. Refrigerant dissipates heat in the air conditioning system to keep your car cool in hot weather.
How Often Does an AC System Need to Get Recharged?
Your car’s air conditioning system is a lot like your home’s central heating and air, and even more closely resembles the system that keeps...
Symptoms of a Bad or Failing Heater Control Valve
Common signs include the heater not working, coolant leaking from under the engine, and no voltage across the heater control valve.

Related questions

How do I use the air conditioner?

When it’s hot outside, you want to be cool and comfortable in your Accord. The air conditioner is designed to do just that. Using it is easy – just follow these steps: Turn on the air conditioner by pressing...

AC knocking when it is turned on

Hi there. It sounds to me as if your AC's fan is interfering with something in the track of its spinning. Also your issue can point to your AC compressor clutch not gripping the pulley correctly. I'd suggest having a...

My heat/ AC blower motor does not work, the blower is good, the resistor has been replaced, and the relay is good. What am I missing?

Hello. There is a service bulletin out relating to the blower motor of 2003 Suburbans: 11046. It pertains to the blower motor electrical issues Chevy experienced during that time. The electrical terminals were essentially melting. It is a fire hazard....

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com