The heater blues

October 25, 2019

Have you ever been driving on a cool morning or a cold winter day and seen the car next to you, and all of their windows are fogged up on the inside? Do you then wonder why this happens, or maybe you are having the same problem?

This is going to be one of the cheapest and easiest things to repair, as well as one of the most overlooked things by technicians. Here at OTC, our students learn the AC gets coolest when you can re-circulate the air inside the car. The heater/defroster only works when you can have fresh air coming in the car, and that’s the big secret to defrosting windows.

There are 2 types of dashboard control. Most domestic cars have MAX AC and normal AC on the controls. Most import cars have a separate lever or buttons that say “fresh” and “recirc.” This is where the problems start.  On cars that have MAX AC on the AC controls head, the difference is the fresh air intake door closes only in the MAX AC position. Therefore, you don’t see windows fogging up on these types of cars because when you are in the heat or defrost position, the door is already open, allowing the fresh air to come in.

Most of these problems come from cars that have a separate lever or button that allows the air flow to re-circulate inside the car or come from the outside. When the lever or buttons are in the recirculation mode, the air is re-circulated inside the car only and does not draw in any fresh air from the outside. Therefore, the heater and defroster do not work as well and you cannot get the moisture out of the car. In the fresh air position, the air comes from outside the car and the heater works again.

So remember: if you want the coolest AC, have the lever/button in “recirc,” and if you want the best heat or defrost, the lever/button needs to be in the fresh air mode.  The best part is you can fix your problems with the AC/heater and it will not cost you a thing. 

(Now, if you are one of those people that likes to drive your car with snow all over it, the fresh air to make the heater work comes from right below the windshield. So if that is covered with snow or ice, you may not be able to get any heat or defroster to work in your car.)

Until next time, have a great day, from us at the toolbox.

Come see us here at Oklahoma Technical College and we’ll show you how to play with engine blocks and a whole lot more.