How to maintain your car's AC during Maryland's humid summer weather

CBS News

6 days ago

High humidity can put stress on your car's air conditioning unit, and in Maryland, the summers often bring hot, dewy conditions.
The high humidity and hot weather can reduce the output temperature of your car's AC system, according to AAA Approved Auto Repair Territory Manager Ben Perricone.
"The difference between 30% humidity and above 50% humidity can mean as much as eight or nine degrees of performance out of your vent," he said.
For example, when it's 96 to 105 degrees and above 40% humidity, a car's max AC output may only be 61 degrees. When it's 85 degrees and 50% humidity, the max output could be 50 degrees.
"Your air conditioner may be working perfectly, but with the heat and humidity, it may not be working as good as it did two weeks ago, when we didn't have 100-degree weather," Perricone said.
So far in July, the Baltimore area has seen more than 12 days where temperatures reached 90 degrees or above, according to data from the National Weather Service.
On days where heat and humidity are high, choose the max AC setting in your car and adjust the temperature with the fan speed instead of climate control, where you select a specific temperature.
"That will be the best way to maintain control, because if you start moving the temperature back and forth, then your compressor, your air conditioning system, will start turning itself off and on, trying to maintain whatever temperature you set," Perricone said.
For cars with larger interiors, Perricone recommends keeping the windows down when you first start your drive. He says it can help get the hot air out quicker.
For small interiors, like economy-sized cars, Perricone said it could be better to just get going.
According to Perricone, the AC compressor does not work at peak performance when your car is going at low speeds, when it's idle or when it's at a stoplight.
"Once you get up to anything over 30 miles an hour, that's where your air conditioning compressor is going to want to be at its best performance."
Once the inside of your car starts cooling down, you can select the recirculate setting. The feature uses already cooled air from inside the car. Perricone said it's easier to cool down 70-degree air rather than 95-degree air from outside.
Perricone emphasized that safety should always take precedent over economy.
He recommends pre-cooling your vehicle if you or your passengers are elderly or have health issues. You'll also want to cool your car down before riding with children or pets, he said.
"Don't worry about the mile per gallon you might lose because the car is sitting there idle for two or three minutes to come down in temperature," Perricone said. "Safety is the most important thing."
To keep your car's AC running at peak performance, cabin air filters should be changed at least once a year, preferably in the spring and fall, according to Perricone.
In the spring, the air filter will catch pollen and clog up over the course of the summer.
Not changing your cabin air filters at least once a year will result in a significant reduction of airflow, Perricone said.
People are keeping their cars much longer now, and Perricone said they're starting to see situations where airflow is reduced because of bugs and debris built up over time in the condenser.
"[It] can significantly impact AC performance long before it creates an issue with your cooling system for your engine," said Perricone. "You may think everything's fine, but the air conditioner just isn't making it, and that could be because that condenser is plugged up with bugs and debris."
Perricone recommends having a mechanic check that your condenser is free of debris. If there is an issue with the condenser, you may notice that the air conditioner isn't working as well at low speed or at stoplights as it does when you drive at higher speeds.
When your car's AC is not functioning at peak performance, Perricone warns against using a can of freon to fix it yourself. This could lead to you overcharging your air conditioning system.
"It could cause it to not work well or even damage the system," he said.
If there's an issue, get your AC checked by a qualified mechanic.