Hello everyone, I know these may sound like beginner questions, but this is my first PHEV, so I’m still learning how everything works. I recently bought a used 2024 Prius Prime XSE and currently live near Boston, MA. With summer coming, I’ve noticed something that seems unusual about the A/C performance. When I park the car under direct sunlight for 3–4 hours, the cabin gets extremely hot. It seems to take a very long time for the A/C to cool the interior down. Previously, I drove a 2023 Toyota Camry Hybrid and a 2023 Chevrolet Corvette. In both of those cars, setting the temperature to 72°F would make the cabin comfortable, and 68°F would feel quite cold. Even after sitting in the sun all day, I would usually feel cold air coming from the vents within about 5 minutes. With my Prius Prime, however, things seem different. If the car has been sitting in the sun, I can set the A/C to 68°F and drive for 30 minutes, but the air coming from the vents still doesn’t feel particularly cold—it feels more like normal airflow. On the other hand, if the car starts out in a garage, the A/C performs much better and even 74°F feels cool. I also have a question about AUTO mode. My understanding is that the A/C compressor needs to be running to produce cold air. However, when I use AUTO mode, the A/C indicator light is not illuminated. Does AUTO mode automatically control the compressor even when the A/C light is off, or should I manually press the A/C button after enabling AUTO mode? Is this normal behavior for a Prius Prime, or could there be an issue with the A/C system? Thank you for any advice!
I can help with part of your question. AUTO does control the compressor unless you change it in the settings. So the light being off doesn't necessarily mean the compressor isn't running. But because your car is used, I'd check to see if the previous owner changed that setting. You access it by going into Settings on the infotainment screen(gear icon), then I think you scroll down to climate settings. There should only be one option on the page called something like "A/C to AUTO". If you set it to ON(the default), then the AUTO setting has full control over the compressor. If you set it to OFF, then you have control over the compressor(mostly) and it will only run when the A/C light is on. As for A/C performance, is your drive mode usually set to Normal or Eco? Choosing the Eco mode puts some restrictions on the climate system. The compressor will try to run at a reduced setting, and the fan will also be throttled down. If you're currently using Eco, try Normal for awhile and see if that makes a difference. A side note about the Prime is that the A/C system is also used to cool the HV battery. I suppose it's possible that the reason your A/C performance is reduced is because the HV batt is hot and the A/C system is struggling a bit to both cool the battery and the cabin at the same time, but I have a problem believing that. I've got to believe Toyota sized the compressor to be able to easily handle both. And it's not like you're living in Death Valley or something with temps above 110F. If you change to Normal and you're still getting substandard cooling, I'd consider having an A/C service done by a dealership. Because of the refrigerant loop that runs under the car and through the HV battery, there's an increased risk of leaks. Between the battery loop and the extra coil in the A/C box, I think the Prime has at least twice as many O-rings in its A/C system as a regular car. And there have been limited reports of gen5 Primes having leaks. It doesn't appear to be an epidemic or a systemic problem, but there seem to be enough anecdotal reports to at least keep an eye on things. Especially because a compromised A/C system could allow the HV battery to overheat and be damaged. And that could lead to a very bad day. But it's your call. Just make sure to ask about any costs for the A/C service before agreeing to it. The gen5 uses the new R1234yf refrigerant, which is VERY expensive.
