Q: Does the Defroster Help the Wiper Blades Work Better?

The short answer is no. Wiper blades squeegee water from the exterior of your windshield and the defrosters remove moisture from the interior of the vehicle, which includes the inside of your windshield. Sometimes it may appear the defrosters are helping the blades work better, but this usually occurs when the outside temperature is near freezing. In freezing and near freezing conditions, the wipers will swipe and moisture will quickly cool leaving a film on the exterior of the windshield. This effect goes away as the windshield warms from the inside.

There is a bit of confusion in regards to a defroster system in a vehicle. It is more than just which vents the air comes out of. For defrosters to work, the A/C system must be operating, and this is the counter intuitive part. How does a system that is seemingly designed to cool the air work to defrost.? Put simply, A/C system cool and dry the air. When your defroster system is working, the A/C is running and drying the incoming air, which is then directed through the heater core to be warmed. This is the defrost mode. If the defroster isn’t on, then air will simply be directed through the heater core for warmth. Drying of the air is occurring anytime the A/C is on. Personally, I prefer a dryer climate inside the cabin so I run the A/C all the time regardless of which vents the air is coming from.

In summary, when the defrost mode is selected, the A/C system is running and the air is directed out the vents below your windshield. This is the quickest way to remove any moisture that has condensed on the inside of your windshield. If the outside temperature is cold, the windshield will need to be warmed to stop the cooling effect on the outside of the glass after the wipers sweep. This isn’t a factor when outside temperatures are warmer.

I suppose it could be argued that the defroster does help the wipers under some circumstances. If we’re splitting hairs, the wipers are only removing water from the glass, defrosters aren’t doing this on the outside in any way. When the windshield is being warmed from the defroster vents, this is the heater system at work. We could break this down even further, but what’s important is they work together to better your visibility. Should you run into any problems with these components, seek assistance from a qualified mechanic who can diagnose your defroster or replace your wiper blades at your own convienience.