Owners Tips

Goof of the Month: Dead Air

Welcome to Goof of the Month! Every month, we ask for stories from our network of mechanic pals which highlight the need to understand one’s vehicle, how to maintain it, and how it works. We read the submissions, check out the stories, and pick the winner, announcing the monthly Goof in our regular column about the most mechanically declined folks on the road today.

This month’s story comes to us again from mechanic Paul Kennaley, of Sudbury, Ontario, who reports that his client visited one day, prepared for a big bill to repair her entire air conditioning and heating system, but got off with a repair of less than 50 bucks.

The Complaint

The customer brought in a few-year-old Mazda3 complaining of inconsistent air conditioner performance and poor performance from the HVAC system in general. “She’d put up with the lack of strong AC all summer, but now with colder temperatures, the poor performance from the defroster system, which relies partially on the AC, pushed her to bring the car in,” says Kennaley.

In a nutshell, sometimes, the AC would blow cold, then cut out, or not blow cold enough at all. The fan was noisier than usual, and the car was taking longer to heat up and cool down than the customer had remembered.

The Mechanic

“I love it when customers give me a list of symptoms that point straight at a fairly common problem with an easy fix,” Kennaley says. “It’s funny – you see the worry on their face, maybe because they’re expecting a big bill. Then, nine times out of ten, it’s a really easy fix. The customer doesn’t have to shell out big bucks, and that puts a smile on their face, and makes us feel good, too.”

In this case, the customer was describing a fairly common issue, to a ‘T’.

The Diagnosis

In most newer cars, the climate control system has an air filter, just like the engine does. “Some older cars have no filter” says Kennaley. “But with a cabin air filter, you get less dust inside the car building up on everything, fresher air, and cleaner HVAC ducting, which prevents smells and allergy flare-ups. Keeping dust and dirt out can also help system components, like the fan motor, to last longer. Thing is, like any filter, the cabin air filter eventually clogs up and needs replacing. But I’d say the vast majority of shoppers don’t even know their car has a filter for its climate control system”.

The Outcome

This is a simple fix: like any filter, when the cabin air filter becomes clogged, the flow of air through the filter diminishes. When the climate control system has less-than-ideal air flow available thanks to a clogged-up filter, system performance suffers. As a protective measure, some vehicle air conditioning systems even turn themselves off if there isn’t enough air flow.

“The heater core, AC and fan may be working just fine – though a clogged filter means the air flow through the system is reduced to nearly nothing, so the fan may be louder, and the hot or cold air just doesn’t get pumped through the car,” comments Kennaley. “The customer’s particular Mazda 3 has two smaller filters instead of one larger one, and replacing them takes 10 minutes or less.”

Great – but if you don’t know you’ve got cabin air filters, you don’t know that they’ll need changing regularly, either.

“This should be done about once a year,” Kennaley says. “But the customer had no idea that there was such a thing as a cabin air filter, so the filters in her car were both original, and about two years past due to be replaced. They were plugged solid. Pretty gross, actually. Looked like a mouse may have even been trying to build a home in there, at one point, too. She was a little freaked out when I told her that!”

Lesson Learned

Paul changed the customer’s cabin air filters in a matter of minutes. In this style of Mazda3, they’re easily accessed by removing a kick-panel near the floor and reaching up inside. Each car is different, tough the replacement procedure is typically outlined in the owner’s manual. Often, it’s possible to change the filters in one’s driveway or garage, with few if any tools, in just minutes. Here’s another example of the importance of familiarizing yourself with the owner’s manual: the customer could have likely replaced the filters on her own, and avoided months of inconvenience due to reduced HVAC air flow in the process.