Fan only cooling

Discussion in 'Clarity' started by JohnT, Apr 24, 2019.

  1. JCA

    JCA Active Member

    I don't believe the remote preconditioning uses the last settings you had; I'm pretty sure it targets something like 75 degrees and turns on the heat or AC itself depending on whether the interior is over or under that. That's been my experience with it also. Otherwise it would be a useless waste for many of us (much of the year it's cool enough for heat or just fan in the morning, and hot enough for AC in the afternoon).
  2. KentuckyKen

    KentuckyKen Well-Known Member

    @2002, that’s a great idea that I hadn’t heard of before, but that makes sense. I sometimes get that smell briefly at the start of AC season mostly. I will try your suggestion. It’s easy to do and and won’t cost any comfort or kWs. In fact, it will be infinitesimally cheaper which appeals to my lingering old hyper-mile attitude. Thanks for the tip.

    However, I don’t think we will be able to do it with the key fob. This is because preconditioning does not allow for any user adjustments. It uses a range of outside and inside temperatures to calculate whether to use heat or AC and even whether to come on at all.
    Attached is the explanation which I think was first shared by @jdonalds.

    Attached Files:

    2002 likes this.
  3. Geor99

    Geor99 Active Member

    Just a thought. After you get home, you could plug in and run your heater on full blast for 3-5 minutes. This would completly dry out any moisture, if you have problems with it.

    It would also potentially kill any mildew.
    2002 likes this.
  4. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Probably a significant amount of drag. "Myth Busters" did a comparison of running a gasmobile with windows up and A/C on vs. running with A/C off and windows down. MPG was worse with the latter case. Of course that was likely with front windows down vs. rear windows down, but common sense suggests that's not gonna make all that much difference. The point is that rolling windows down creates aero turbulence, which increases drag enough to make a real impact.

    However, that comparison may not apply to running a PHEV under battery power. Use of A/C and cabin heating impacts EV range more than gasmobile MPG. EVs are designed to be more energy-efficient than gasmobiles, but the flip side of that is that they have less energy to waste on heating and cooling.

    Bottom line: We need to see a comparison similar to what "Myth Busters" did, but using either a BEV or a PHEV using EV mode only.

  5. Ken,

    Not sure this is true: I came into work this am in the cold, and had the fan only setting on (manually selected AC off). When I left today, I preconditioned the car (it was ~98 degrees when it started, ~80 outside) and the temp ended up going up--the fan ran, but the AC compressor never came on. The AC works fine when selected. It could be that there's something wrong with the car, but another possibility is that the AC recalled that I manually turned off the compressor and kept my setting. I'll try it next week and work and try to figure it out.

    p.s. I've been doing what 2002 suggested for years in my Subaru.
    p.p.s. Pushmi - The heat is basically free in a ICE vehicle (waste heat) but we create it using resistance, which is expensive. ACs (and heat pumps) move existing heat, and are more efficient--the AC in our car should be identical to any electrically driven AC (vs belt driven compressor) in an ICE car, and should be relatively efficient. I'd expect the mythbuster's conclusion to hold still.
    Last edited: Jun 12, 2019
  6. KentuckyKen

    KentuckyKen Well-Known Member

    Thanks for the observation. We need all the data points we can get to be able to reverse engineer this car.
    That’s a puzzler since this diagram and text (first posted by @jdaniels, I think) seemed to indicate that it worked on a set of inside and outside temps automatically and wasn’t user selectable. Perhaps there are exceptions in the algorithm or some set of conditions that we haven’t got info on. Keep noticing what it’s doing and keep us updated.
    Attached is a repost of that diagram:

    Attached Files:

    insightman likes this.
  7. JCA

    JCA Active Member

    I will try to remember tomorrow to make sure the AC is off when I get to work to get another data point; we're having 100+ degree weather so it's easy to tell if the preconditioning cools it down in the afternoon! Most spring days it's quite cool in the morning, so the AC is off, and warm enough to need it in the afternoon, and I'm very certain it's preconditioned fine on those days. I don't use the auto button, and turn the AC on/off manually, because while I'm fine to cool to 70 thermostatically, I *never* want to be blasted with heat in my car if it's in the 50s or 60s already -- especially not expensive electric heat.

    The preconditioning stops when you unlock or open the door (not sure which) so it can be hard to tell if it was operating, and when you start the car I believe the climate control settings are back where you left them, so you'd have to turn on the AC at that point if it had been off when you left it, even if it had been used for preconditioning.

    I've also had the car seem to get the signal or not started it soon enough and still be very hot inside when I got in (even when I'd used AC in the morning). It feels like under 5 minutes (the time to walk to my car) doesn't help much; turning it on 15 minutes before I leave results in a nice cool car when I get in. It takes the a couple minutes to get the signal and start up the system, and it takes the system several minutes to really cool and start making any appreciable difference when all the materials inside have been baking for hours.

    From outside my car, the AC running is louder than the engine idling.
  8. insightman

    insightman Well-Known Member

    In my experience, opening the driver's door shuts off preconditioning, but opening other doors does not.
  9. JCA

    JCA Active Member

    So I stand corrected -- I made sure the AC was off today, and upon preconditioning the car was just as hot after 20 minutes. I even started preconditioning again while sitting in the car, and sure enough it was just blasting hot air. So apparently at least the AC control needs to be set right. Tomorrow I'll see what happens if the AC is on but the temp setting is high -- will it cool to the previous temperature setting, or to ~75?

    I am a bit disappointed that it doesn't automatically turn on (or off) AC as needed, but at least now I know to turn/leave it on when I park in the morning.
  10. I'm disappointed too. I'm wondering if there's a way to tell the system that it's ok to turn the AC on when it starts preconditioning...without actually turning it on. It would be a pain to have to turn it on when I park it just so I can run it later.

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