Better check the heater

Happy Fall!

By Steve Schaeber, MACS Technical Editor

It’s one of those cold mornings, (like the ones we’re starting to get here in the Philadelphia area), and maybe you go out to your car and find there’s no heat blowing out of the vents. Ok, so maybe your first thought is that you didn’t give it a chance to warm up yet. Nope, that’s not it. You’ve been driving around for about 10 minutes, which is plenty of time for the engine to reach operating temperature in just about any car on the road. So what may be the problem? Here are some answers to common questions received by MACS.

What are common reasons a heater or defroster stops working?

There are many reasons why a heater or defroster may stop working. Some issues could be related to the electrical system, such as fuses and wiring, blower motor fans or operator controls. But there are also mechanical systems to consider, such as flap doors that control air flow, mix and direction. Other issues could involve the engine coolant, commonly referred to as antifreeze.

S1610153 - Photo 1

A first step in diagnosing HVAC concerns is to verify proper operation of the dashboard controls.

Can a malfunctioning heater or defroster be a sign of a larger problem?

Sure, and this is where a professional technician can really be helpful. Larger issues may arise with components such as radiators and heater cores, water pumps, thermostats, engine cooling fans, belts and hoses, or even electronic sensors found throughout the vehicle.

What does it mean if my vents are dirty or moldy? (Do they just need a wipe-down or something else going on?)

It could be that you’re just seeing dust that would otherwise naturally be found in a vehicle, or it could be bigger than that. Many vehicles today are equipped with a cabin air filter, which needs to be checked and replaced periodically. Ask your service advisor if your vehicle has this feature.

S1610182 - Image 2

Dusty dashboards may just need a wipe-down, but could also indicate a cabin air filter issue.

Is there seasonal maintenance I need to do on my heater or defroster?

Your vehicle’s engine cooling system is one of those areas which require periodic maintenance. Sometimes it’s no more than a visual inspection; other times a coolant flush may be in order. Be sure to check your owner’s manual, and follow any manufacturer recommended maintenance intervals.

What should I look for in a repair technician?

First, you should try to find someone you can get to know. There’s nothing more important than being able to trust those you do business with, especially when it comes to your vehicle. If the technician is working on your vehicle’s A/C system, find out if he or she is certified under Section 609 of the Clean Air Act by an organization such as MACS to properly handle refrigerants. In addition, MACS supports the voluntary certification of technicians by the National Institute for Automotive Service Excellence (ASE).

S1610187 Mr. MACS - Copy - Image 3

Become certified and proudly display your credentials. You’ve earned it!

Do you provide technical support for heating and air conditioning? Want to share some of your stories with MACS? Send them to

If you’re a service professional and not a MACS member yet, you should be! Become a member and receive a technical newsletter with information like what you’ve just read in this blog post visit for more information.

You can E-mail us at . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.

Mobile A/C professionals should plan to attend 35th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Meet me at MACS Make Connections that Matter, February 5-7, 2015 at the Caribe Royale, Orlando, FL.




About macsworldwide

Mobile Air Conditioning Society (MACS) Worldwide Founded in 1981, MACS is the leading non-profit trade association for the mobile air conditioning, heating and engine cooling system segment of the automotive aftermarket. Since 1991, MACS has assisted more than 600,000 technicians to comply with the 1990 U.S. EPA Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment. The Mobile Air Conditioning Society (MACS) Worldwide’s mission is clear and focused--as the recognized global authority on mobile air conditioning and heat transfer industry issues.
This entry was posted in Automotive, Automotive Aftermarket, Automotive training, Electrical/Electronic and tagged , , , , , , , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.