Window Fogging in Cold

Warmer humid air is condensing inside of the window when outside is cold. The quickest way to deal with fogging in this situation is to open a window a little bit to get fresh and usually drier air in and bring the temperature of the cabin lower.

If you can't keep the window open, without turning on the front defroster, you can usually defog the front window if you set the direction of airflow to the window manually. You do not have to have A/C ON. Airflow to window automatically turns on the compressor.

 

stop singing in the shower

 

I have had a similar issue here is the south as the weather has changed.

My Choice is ALWAYS SAFETY FIRST. Turn on the defroster--it works very quickly.

It is not worth an accident to have an "all EV commute".

 

Your body and lungs always emit moisture as part of respiration, a necessity for life, boosting interior humidity. When the windows are colder than the dew point of the warmer interior air, you will get condensation.

On top of this, it is possible that you have other unwanted moisture stored inside, in the form of wet floormats, or wet boots or coats or other clothing. These will add to the interior humidity problem.

Lose the recirculation, at least when the A/C dehumidification is turned off. Bring in fresh outside air to push out the higher humidity interior air. This will help but is not always sufficient. If you have unwanted moisture stored inside, take it out. Remove wet clothing or towels. Take wet floormats out to dry in the house or garage. Wet carpets will need more effort to dry out, and may need fans and/or heat inside a garage. Use a desiccant (DampRid is one example).

Or you may just need to use ICE heat to warm the windows.

 

i would think the heat pump and floor/defrost setting should be sufficient

 

Use fresh (outside) air. Set mode to heat/defog, crack windows slightly. Use AC if still fogging up.

If one of the above kicks on the engine, just go with it?

 

All the indication from the car, no warm air coming, or energy diagram not showing arrow from the battery to the HVAC seems to suggest the climate control OFF is no heat pump. In this setting, there is no fan running and your temperature setting is dimmed. However, I noticed if you have ICE running, you can feel the warm air from the vent without blowing. But under strict EV operation, I think you are getting just warm air.

This is a hard call. My understanding it that for the six different modes of operation PRIME HVAC has, it can not perform gas injected heat pump AND electric compressor operated dehumidification at the same time. If you recirculate your cabin air, you are not going to get rid of humid air unless the compressor runs to dehumidify, but if recirculation if off, then colder fresh air from outside must be heated by the heat pump. Both situations demand more energy from the battery. I think it all depends on how humid and how cold the air is. And I think it is more case by case which operation is more efficient.

 

That is my understanding. I will try to find the ref where I read this and post it if find it.

But better yet, I contacted Linear Logic, a maker of ScanGuageII and got a suggestion for a X-gauge command to use to check what mode the HVAC is operating at any given moment on PRIME. Copied below is the command I supposed to use, but I am totally unfamiliar with X-gauge at moment. It will take sometime to play with the gauge and setting to get a meaningful data. 1-6 are the mode of operation. The comments in ( ) are mine. As you can see, mode 5, the gas injection heating (aka heat pump) is a different mode from the rest of HVAC modes. I believe 7 and 8 are Idle in which HVAC is OFF and Init which must be initialization when the system is turned on but not ready yet?

Heat Pump Status (State)
TXD: 07C4217A
RXF: C461057A3000
RXD: 2808
MTH: 000100010000
NAME: HPS

1 = Cooling
2 = Series Heating/dehumidification (40-60° F/4-16° C for serial)
3 = Parallel Heating/dehumidification (32-40° F/0-4° C for parallel)
4 = Heating (I believe this is conventional heating using ICE)
5 = Gas Injection Heating (This must be the "heat pump")
6 = Defrosting
7 = Idle
8 = Init

 

This thread has some refs, I read. But none seems to explicitly state that Gas injection heating (aka Heat Pump) can not operate at the same time as dehumidification mode. My best guess is that by inference that six modes operate separately, and dehumidification modes are linked to three of them (Series, Parallel and Defrosting) but not with the gas injection heating mode.

How does the heat pump work in a Toyota Prius Prime plug-in hybrid? | PriusChat

 

I don't know the technical differences between mode 3 Parallel Heating/dehumidification and mode 5 Gas injection Heating. But ref seems to suggest the mode 3 works in temp range (32-40° F/0-4° C) whereas mode 5 works down to 14° F/-10° C. What I don't know is mode 3 heating is using the heat pump just not gas injected or without heat pump but using ICE generated heat.

Even if mode 3 heating does involve a use of the heat pump, if the temp range is restricted to 32-40° F/0-4° C as stated, it is likely there is no dehumidification that can function below 32° F/0° C. So, if the temperature is below freezing down to 14° F/-10° C, the heat pump must be working alone in mode 5 without dehumidification.

 

Like @Tideland Prius, I don't have a hard number to support my claim, but AUTO ON, AC OFF may not be the most efficient. It certainly is the most convenient and worry free, since you don't have to change much of anything.

When in AUTO, I don't think you can select the direction of flow of air or fun speed. They are automatically selected. To do that you have to select them manually, which cancels AUTO, I think? I may have to confirm this on my car, but that's what I can recall.

Also, either in AUTO or Manual, if the direction of air flow is to WINDOW, the electric compressor turns on regardless of A/C setting. Thus I believe if all you need to defog is the front windshield not involving the side windows, A/C ON is not necessary.

I have been successfully using following setting on my car down to 14F this winter to conserve battery SOC and keep the cabin comfortable and defogged. AUTO OFF, A/C OFF, Recirc OFF, ECO mode, S-Flow driver priority mode, set temp 70, set fun speed to minimal needed (usually 2 is enough to keep me comfortable and keep the windows defogged), and use selection of air flow to the cabin for heating only or to Window for defogging. But unlike you I do use HV mode to generate initial heating I need to conserve battery power for actual EV drive rather than for heating. So it may not work for all EV drive like you do, but it should be more efficient than AUTO ON for most part, and more importantly it will keep the front windshield clear.