Prius Defogger Performance

Did you have the AC on as well? Blowing hot air will clear the part of the window it is hitting, but AC will also dehumidify the air, clearing the rest of the glass.

 

i've never had any problem defogging, but the coldest here is usually only a few below 0 degrees f. do you feel like the damper is allowing full flow to the windshield vents?

 

Mine works just fine in Edmonton. I leave it on "auto" and press the front defog button. The rear defog is the electric heater traces on the hatch glass and they work fine as well. Make sure the system is taking in outside air, not recirculating inside air. On auto it does this automatically.
Also make sure you don't have wet carpets. If that's a problem get a set of "Weathertech" carpet protectors, the "laser measured" ones.

 

I concur, the heater is fine so far, but it's not so easy to keep the windshield clear, particularly in cold and humid weather. I think it helps to close-off some of the air-vents you aren't using.

I had my rear-defogger in for service, because I didn't think it was working properly, but they said it checked out fine. These things are normally very power-hungry, therefore it's a bit under-rated to save power.

 

I don't think the AC compressor will actually come on when outside temp is below freezing even if the light shows on. Something to do with compressor/coolant not working below freezing ambient. AC on during defrost/defog is usually for humid conditions, not extreme cold.

I think our OPs problem is that it's just too friggin cold for that little 1.8L engine to put out any heat!

 

On my 2013, AC comes on automatically once you press front defogger. If I turn AC off and try to defog, it's almost useless. Make sure AC is on.

 

-40 and car fully loaded! impressive Prius!

 

I think the problem is humidity more than temperature. But more heat would definitely help.

 

This would be a situation where people around here would partially block the radiator.

 

That's right. It's needed not only for heat, but also to minimize unnecessary aero drag. It's strange Toyota doesn't bother to include it, when even cars as inexpensive as the Nissan Note have active grill shutters.

 

I've been wondering about this too. I think they don't have grill shutters for a few reasons, one being it could be added cost/complexity (notice the complaints about the subpar interior even on higher trims?), but I think the bigger reason is that Toyota thinks people are morons, and will forget to open them back up when it gets warm. And if they damage their engine because they forgot to open the grill, then some lawyer may throw a lawsuit in.

 

Exactly. And a well-designed coolant thermostat would accomplish that job anyway. Using shutters is just a more expensive way of doing the same job.

 

The active part means they automatically open and close. No one would trust the average person to manually open them. The don't replace the thermostat. The airflow through the engine bay can cool the engine even when the thermostat is closed.

 

My car has been doing fine lately. Started right up in -18F Thursday morning. Heat came on quick during my 10 mile drive to work. I had it blasting most of the way. The car doesn't seem to be as well insulated as others I have owned. No worries though!