Backseat AC not working

Not to be condescending but give the owners manual a good reading.

 

AND ......in the future please consider NOT posting the same question in more than one sub-forum.

 

the vents in the back are actually cooling ducts for the battery.
the back does get a bit stuffy when it's hot and if you crank the ac to high the front passenger gets way too cold.

 

It’s also important not to block those vents as they are for cooling the battery as mentioned above.

 

Well, it helps to be clear about which vents are meant.

Vents that you see beside the rear seat are intakes for air to cool the battery, they aren't conditioned air for you.

Vents that you see beneath the front seats, aimed at the rear passengers' toes are conditioned air for the rear passengers. They only blow when the system is set to blow on feet, which is usually for heating. You can make them A/C vents if you set the outlet to feet with the A/C running, but only to get popsicle toes.

 

Perhaps I can help with a "not so obvious" cooling strategy?

To effectively cool all passenger seating positions, one can draw an example from how some modern building designs are implemented (see airports, malls, convention centers, etc). The key is to use the car's ceiling surface as a carrier/distribution mechanism for any passenger in the rear seating positions. Simply adjust all airflow vents to point to the roof-line of the vehicle and if possible, eliminate/close any of the foot and window vents. This means front passenger and driver will forgo direct cooling in order to make it work well.

This approach works very well with aerodynamic roof shapes like that in the Prius since this way, the cooled air will travel the furthest and will literally drop down on all passengers. Not very intuitive at first, but do give it a try and see how it works for you.

Cheers

 

Yeah. This is a technique I've used in every single hybrid & EV I've owned. I simply cannot remember a single vehicle that had effective cooling for the rear passengers.

I have yet to notice a big difference in cooling effectiveness between the center vertical vents in those with the 11.6" versus the regular LE vents. We always adjust the four top vents to direct the airflow to the ceiling with the venting mode set to "face". That's it.

 

I can see cool air carried along the roofline being dispersed in rear seats, but how about warm air? Would they effectively decent to warm the rear seats? Not that I have ever used any of the rear seats in my PRIME for passengers, I will more likely be needing heating than cooling in the back. We got so spoiled with our Pathfinder with a triple-zone HVAC system. Rear seats have dedicated vents and controls in the back.

 

It was extremely helpful in the 4Runners I owned in the past as the air conditioning felt like it was from the 70s. Just bounce the air and let them enjoy. I keep the side vent for me though as I run hot lol.

 

I bet it would work from a thermometer's point of view, but it might not be as comfortable to human passengers as when using the floor vents.

I can't say I've a habit of pointing all 4 vents at the ceiling, but certainly the center two, in every air conditioned car I've ever had. Works great.

 

Anytime I've been a rear passenger, the pointing the AC vents at the ceiling trick hasn't worked. Cars are different from buildings. They are poorly insulated and often start out at extremely high temperatures. On hot days they use continuous airflow to keep passengers cool, because they can't cool all the mass of the interior quickly enough to make the ambient temperature comfortable.

As a rear passenger I've always been more comfortable with even a sliver of cold air blowing straight back from the front vents. Cars with rear vents are far more comfortable of course, but those are usually found in larger, more expensive, and more luxurious cars.

On one hot drive in another car, I tried setting the air to blow out both the dash vents and the floor vents, since there are rear floor vents. I'm not sure if it helped the rear passengers at all, but I was uncomfortably warm in the driver's seat because the AC couldn't keep up with the extra airflow on a 110 degree day. The Prime seems to have a more powerful AC system as a byproduct of having a heat pump and cooling the battery, so it might work a little better even with extra airflow.

 

We always had the same problem. But we seem to get better results by doing more like @m8547. We aim the center ones between the front seats, and a little bit above horizontal. We aim the outer vents as close as we can to shooting between the door and the shoulder. Also, I take it our of ECO HVAC mode an often crank up the fan, at least for a while.