Front Defroster - EV mode

My understanding is that's what it's supposed to do. It needs to use the air conditioner to cool the air, meaning de-humidify it, then it needs the engine heat to warm it back up again.


iPhone ? Pro

 

it would be nice to have heat only front defrost. a/c isn't always needed.

 

Yes, selecting the "FRONT" defogger will turn the ICE on, as this defogs the windshield with heat exchanged from the ICE water jacket. So the ICE will have to warm up. But the Prime has a Heat Pump that is capable of providing "ECO Heat/Cool", while remaining in EV Mode. On the "Climate" screen, select the "AUTO" selection, and there is a deflector selection for Windshield and feet. This will provide (just) enough defogging for most applications. I have been using the "ECO Heat/Cool" to defog my windshield on trips as low as 16F without the ICE turning on. If it is too cold, or too many people in the car (high humidity), you will probably need the "FRONT" defogger to use the ICE to generate enough heat and airflow to defog that (huge slopped) windshield.

 

I just noticed this last week. It surprised me when the engine turned on. I'll use the defrost on the screen next time.

 

Page 87 of the owner's manual has this on it:

 

make sure you set the temperature to 65 F and set ECO climate too

 

I understand that the ICE turns on when the front defogger button is pressed, but why doesn't it turn off when the defogger button is pressed again to toggle to off position. The front defogger is very efficient and in the current November weather and clears the windshield in a minute or two. At that point, I'd like to turn it off, but the only way I seem to be able to do that is to open the climate control screen and switch the system to off.

From what I just read in this thread, the front defogger button switches the Prime from EV only mode to hybrid mode, so maybe I just need to press the EV/HV button to go back into EV only mode. Even so, it's confusing and not particularly convenient. Am I missing something here?

(BTW, the Prime Advanced remote climate control using the smartphone Entune app works well. We used it this evening: we parked at a ChargePoint station in a parking garage near a theatre where we were going to see a play. When the play was over, I used my smartphone to start the Prime's climate control. By the time we'd walked the five minutes back to the parking garage, the Prime was sitting there with heat pump running and all comfy inside. This is a very nice feature, indeed.)

 

Once ICE kicks in (for whatever reason) It has to warm up to satisfy emission requirements once ICE has fully warmed up it will shut off (provided you turned off the front defroster beforehand)

 

I adjust the airflow to include the front and set a high heat and fan. Within a minute or so (in Dixie), global warming wins.

Bob Wilson

 

I tried this yesterday, and it did seem to work reasonably well, as a presumably heat-only defogger. I couldn’t verify 100% for-sure that the engine didn’t come on, but I’m pretty sure it didn’t.

Darned ICE is such a vampire: Sometimes it’s so quiet you can’t tell when it’s on. Toyota should add a noisemaker to it, like they did for backing up! (Yes, I’m kidding.)


iPhone ? Pro

 

I’ve been using fan only with defogger & works very well - temps so far as low as the 20s. A/C and auto off, ICE has stayed off. Fans seem very loud, though. Not sure if they’re louder than other cars or it just seems to be the case because I’m running on EV.

 

What kinda surprised me was that the ICE seems to come on when you press the front defroster button, even if the cabin temperature is set to “Low.” I can’t confirm that it always does so, but at least often, and based upon the above quote from the manual, it’s likely that it always does do so.

I was hoping it would keep the engine off and blow *cold*, air-conditioner-dried air across the windshield. That doesn’t work as well as *warm*, dry air, but it does work, and conceptually would allow the ICE to stay off.

I’ve decided that the best thing we can do to keep the windows from fogging up it to keep their inside surfaces clean.


iPhone ? Pro

 

from a liability standpoint, i think toyota wanted to give the windshield every opportunity to clear, when the driver decided the vent flow direction of feet and windshield wasn't enough, and pressed the front defrost button.

 

Thanks... that makes sense. Because the windshield clears up so fast, I've never been patient enough to wait to see when the ICE would shut off.

Last evening I ran it for a couple of minutes and the Entune ECO dashboard reported my mpg for the day had dropped to 561.2 mpg from its usual all-EV 999.9 mpg. Pretty sad when clearing one's windshield cuts one's fuel economy by 44%!

 

Except, your normal may have been 1999.9 or higher

 

what happens when you use the defrost vent position, not enough clearing?

 

You mean like the mode in the pic above? If so... totally depends on the conditions. One thing I have noticed when the inside of the windshield fogs up on the Advanced is that the section right in front of the HUD does NOT fog. Whatever they put on the inside of the windshield there, I want it on the ENTIRE windshield.

Otherwise, I've noticed that under high humidity conditions and 32 to 40 degrees F that even with the temp setting at 75 and fan on level 5 that it takes about forever to clear - and that's without any real ice. The pro is that with heat pump heating, the warmth comes up pretty darn fast - FAR faster than with radiator type heating. I've started using the A/C dehumidifying trick to see if that does any better.

 

I don't see much of a difference.

 

great, that makes it easy not to start the ice by pressing the defrost button, unless you absolutely have to.
that's a big advantage of the prime over the pip, i have to blow cold outside air on the windshield and feet to defog, and of course, there's no way to defrost unless you start the ice deicer.