Bugs? (A/C and auto-high beams)

The HVAC is working the way it's designed to work. The default setup for the gen5(and probably all new Toyota models) is that the car fully controls everything, including the A/C. When in full auto mode, it's not going to turn on any extra lights. This means you've actually been running with A/C on all this time. Just because the light is off, doesn't mean the system is shut off. The car will vary the speed of the compressor from 0%-100% to maintain the set temp.

If you're dead set on running the system the old way, there's a setting you can get to in the infotainment screen. Just dig a bit(I think it's under My Settings>Climate, but I could be wrong). It's the only option on that particular screen. It's called something like A/C Auto. If it's set to ON, then the car controls when the compressor is running or not and the A/C light on the climate control is always off. If it's set to OFF, then the driver controls when the A/C system is active, and the light indicates the system status.

If you want to run in the full auto mode most of the time, but still want to shut the A/C off every now and then without digging through the settings, you can do so by pressing the A/C button twice. The first time forces the system on, and the second time shuts the system down until the next time the Auto button is pressed.


Can't help you much on the auto high beams. I tried using them, but they were just too finicky for my conditions. They were either never on, or they were constantly flipping back and forth from false positives(reflections off road signs, lights from parallel roads, farm light poles near the road). I've just given up and now do it manually.

 

It works the same way on my 2025 Camry.

 

Hmmmm. Under the default settings, I think it would still be on after your button presses, but I'm not 100% positive.

I believe the logic of the system is set up so that if you are on Auto and you change any setting, the only thing that is altered is that category of settings. So if you alter the fan speed, the fan subsystem is the only thing not being controlled by the car. But I don't know that for a fact.

You could test it by altering the fan speed and then changing the temp to the extremes. If the HVAC shifts the air from the dash to the floor depending on the set temp, then the overall system is still in Auto and only the fan speed is being manually controlled. If this is the case, then I would expect the A/C to still be controlled by the car.

But if the output location remains constant even after major temp changes, then I don't know which way the A/C would go. I guess the best way of testing that would be to set the fan to max, then vary the temp to see if the air gets cold. If it does, there's your answer.

Again, you can just change that setting(Auto A/C: OFF) and you'll have full control of the A/C system. Or you could just press the A/C button twice to force it off.

 

BTW, one of the reasons the new cars are set up this way(Auto A/C) is to prevent mold build up in the HVAC system. The new climate controls are far "smarter" than the older automatic types. They monitor many more parameters and may make choices that might seem counterintuitive to us but actually have rationale. So they'll monitor inside and outside temps, humidity, and usage time(among other factors) and run the A/C or vents to keep the humidity down in the fan box with the different coils. Overriding the Auto A/C will prevent this from happening.

 

It can be.

The auto light being on means "everything is auto". Auto light off means something is not auto - that could be the A/C or something else. The auto light will go off when you manually adjust any control. That control is then manual, others remain auto.

If the A/C is auto, its light is off, same as other indicators go blank or off when auto.

So you can't immediately tell from the lights whether both lights off means that the A/C is off or auto.

But as Hammersmith says - press the A/C button until its light is off, and you'll ensure it is manual and off.

 

Pull the headlight stick as if you're flashing the high beams - that will turn them off for a while, before it goes back to auto.

 

The pull will give you high beams - but then you had them on from auto anyway. But it also deactivates the auto, so when you let go, you're back on dipped beams.

 

Double-checked the US manual, as I know the AHB system you've got is different than the AHS I have, but this function is the same. Relevant text:

 

How would you know? The things that are auto are not displayed (fan speed, A/C, vent position, inside/outside air). Selecting a function reactivates its display but leaves the others blank and auto.

All of the fan speed, vent position, A/C and inside/outside air indicators go off when Auto.

It is a bit odd - I'd like to see what it's doing.

When A/C is auto, first press of A/C switches it to manual, and always sets it to ON. (Maybe because the light was off, so they want you to see a light change?). Second press changes it to OFF - at this point it's simply toggling the manual setting.

Yes, that's what it does. Normally pressing AUTO sets everything previously listed to auto, leaving just the temperature selection as the user choice. The only variation on that is the config option to make it never do auto A/C setting and have that always manual. But after you've pressed AUTO, you can then switch functions back to manual by adjusting them, one-by-one, until the next time you press AUTO to send everything back to automatic.

 

I drive in ECO mode most of the time, and I believe it runs the AC at half capacity. I set up the custom mode to be the same as ECO mode, except for the A/C running at 100% capacity. I only had to use it once or twice last summer.

 

If Auto works like on the Camry, it no longer shows fan speed or air direction. My 2017 Prius showed both when on Auto.

 

If you have an OBD-II scan tool that knows the Prius PIDs, it can show you the watts being consumed by the A/C compressor. When zero watts are shown, it's off.

It is variable speed, and can be on at anywhere from around 250 watts to around 2500. You can see the level it's running at on the scan tool.

Selecting ECO mode does put a ceiling on the max power it will be allowed to use. I don't think the ceiling is as low as half, though.

 

i thought the Prius Prime had a heat pump, not an electric AC compressor.