AC doesn't work at high RPM

Are there any warning lights? Ever had front end accident or fan replacement?

 

1. Regarding the "fan", we are talking about the two radiator fans; not the cabin ventilation fan. I suggest you turn on the AC compressor, open the hood, and make sure that both fans are running and sucking air from the front of the car and blowing it through the radiator.

2. There is no reason for the AC to stop working at high engine RPM, but it might stop working at freeway speeds if the radiator fans are blowing in the wrong direction.

 

I suggest you determine in what direction are the radiator fans moving air.

 

From the grille, towards the engine. Same direction as the air would naturally flow as the car moves forward.

 

Check for flow in the inverter coolant reservoir. I've heard that if the inverter overheats then it prevents the aircon compressor from running.

 

Unlike a conventional car, where "high RPM" can happen for various reasons (high road speed, downshifting, etc.), the CVT-ish nature of a Prius means that engine RPM is pretty much solely determined by the amount of power being demanded (or dissipated, in the case of full-battery deceleration), so "high RPM" in a Prius is pretty much a synonym for near-maximum power situations, and that's where the clue probably lies. If there is any problem with cooling the inverter, near-maximum power moments are likely to be when it is noticeable. At the highest power demands, the car may even be programmed to shed the A/C for more available propulsion; even pretty old cars had that ability. Usually that's only for a moment during acceleration peaks; do you have a situation, like a long uphill, where you need maximum power from the car for a longer period?

-Chap

 

So, have you checked the inverter coolant reservoir for fluid turbulence when the Prius is READY, which would show the inverter coolant pump is working?

 

The Prius AC Compressor operates electrically, from the HV system, completely separate from engine speed. However, as with most modern vehicles, the AC can be "cut off" during high load (full throttle, or nearly so) conditions to provide the most power from the drivetrain.

It is perfectly possible that this is happening to your car, either due to full throttle, high inverter temperatures or some other load causing the system to de-activate the AC compressor.