Can A Faulty Air Conditioner Make Your Car Run Poorly?

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Air conditioning is more than a luxury if you own a car in a hot or humid climate. While you might be able to get by without air conditioning in a well-ventilated home, stepping into a car that's been out in the sun can often feel like entering a sauna. That first blast of cold and refreshing air can help get your cabin temperatures back to a livable range.

In most cases, the first warning sign of AC trouble will come when your system can't seem to bring those hot temperatures back under control. However, problems with your air conditioner can also have some other effects on your car. If your air conditioner isn't cooling as it used to and you're also noticing drivability issues, the two problems may be related.

How Does Your Car's Air Conditioner Work?

Your car's air conditioning system is surprisingly similar to the air conditioning system in your home. An automotive air conditioner will have many of the same parts, including a compressor, evaporator coil, condenser coil, thermostatic expansion valve, and various sensors and electronics. And, as with your home air conditioning system, the compressor is the most expensive and critical component.

Since the compressor draws so much power as it runs, most cars connect it directly to the engine via an accessory belt. Your car may use a separate belt for the AC, or the compressor may use the same belt as other accessories, such as the alternator and power steering pump. Some vehicles may also use purely electric compressors, although this design is less common.

When the compressor turns on, it can draw a surprising amount of power. Most cars compensate for this extra load by increasing idle while the air conditioner runs. You can usually observe this by carefully watching your tachometer. Turning the air conditioner on in most cars should cause the idle to jump by a small but noticeable amount.

How Does a Faulty Air Conditioner Affect Your Car?

A failing or overloaded compressor in your home AC system may cause your lights to dim noticeably or even trip the breaker for the AC circuit. Likewise, a faulty compressor in your car will place an abnormally high load on your engine. Some vehicles may compensate automatically by increasing the idle, while others will run or idle poorly.

These symptoms can indicate a problem with the compressor, especially if you can hear a banging noise as the AC turns on. On the other hand, less serious problems can also cause your compressor to struggle. For example, low refrigerant levels can freeze the evaporator coil, resulting in an overworked compressor, short cycling, and, in some cases, noticeable idle problems.

Of course, a rough idle can also result from other engine problems. Issues with your car's throttle or idle control valve can affect the engine's ability to compensate for the AC load, resulting in poor idling. Since there are so many potential causes for these issues, you should always have a trained automotive AC technician diagnose any problems you are experiencing.

For help with vehicle AC system repairs, contact an auto service in your area.