Seems to be okay now. Took a 4,500 mile trip to the Midwest in December and January and didn't notice any problem. Of course we didn't experience any sub zero weather on the trip as we did in Montana during the Thanksgiving holiday.

 

Sorry to revive an old thread but I have some info on the rear defroster time intervals.

It turns out, pg 129 of the manual states that the rear defroster/heated mirrors will remain on between 10-30 minutes depending on the outside temperature. This happens at above 32 degrees F.

***If the temp is 32F or below, then the timer function of the defroster/mirrors will NOT auto switch off.

So the shut off is TEMP based, and time limited if above 32F.. After installing heated mirrors on my EX 6MT USDM, I noticed the ICM controls this function and not a simple timer.

If anyone is having trouble with the defroster, check to make sure your defroster is heating up, and verify the outside temp sensor is working properly. The ICM is using these sensors to limit the defroster function.

 

I've only had my Fit for a month but I've noticed the rear defroster/defogger doesn't go off at all, no timer. And in fact twice when I got into the car the defogger was still on, it never shut off when I turned off the car on the previous trip.

So it sounds like my experience isn't normal, huh?

 

I'm assuming the defroster switch was engaged? As mentioned according to the manual the mirror and windows will stay turned on 10-30 minutes then turn off if above 32 degrees F outside. It makes no mention of how long the circuit stays de-energized/off before it resets and turns back on.

 

The rear window has what they call a defogger, as opposed to defroster. I don't think it is intended to be able to melt frost, although it might be able to very slowly deal with a very light layer.

For the front defroster, with anything other than a very light film of frost, you'll have to get outside and scrape. The front defroster blows hot air onto the windshield so you can expect it to melt a light film of frost but anything heavier than that and you have to get outside with a scraper. What I do is I have winter grade windshield wiper fluid (all year long). Spraying that, along with blowing hot air onto the windshield, will help make frost lest clingy, so that it is easier to scrape off the windshield. To make sure fog doesn't accumulate on the inside of the windshield, make sure the system is not set to recirculate. The AC compressor seems to go on automatically when you switch the air output knob to defrost-defog (furthest position clockwise) so there is no need to press the AC button. I don't think the compressor goes on when the knob is in the dashboard vent position. Sometimes I want to warm up my hands quickly so after the lblow ow water temperature indicator light goes off I move the temperature knob to maximum heat, move the airflow knob to dashboard vent position, and hold my hands in front to the vent. To make sure the windshield doesn't fog up, I keep the system in recicrulate and I also press the AC button.

 

In Manitoba; I had to add a little deflector because of this problem. I cut a floor register plastic deflector in half and attached with double sided tape to the top half of the side deflector on my 2007 Fit. It redirects enough warm air to keep the buildup on the lower part of the windshield.

 

Alli can day is"ditto" on the icing and fogging problem and lack of rear defining as well.
​​​​​