Air Conditioning: Cold at high speeds & hot when slow

Maybe you're low on Freon

 

Are both fans running when you turn the AC on?

 

well the dealer should know if it needed a charge. They shouldn't just charge it for no reason.

 

could a weak hv battery cause this?

 

if the dealer did charge it, then there is a leak. no need to charge a full system.

next time it starts blowing warm, make sure the fans are blowing on high speed.

just for grins, look at the condenser to make sure its not blocked with leaves or debris.

 

I had a 2005 prius with same issues found out the compressor was worn out . one way to test this is start car in driveway turn air on leave run & take a garden hose on run over compressor while running, the compressor is a electric compressor so no belt , after a bit of time doing this go back in car & see if any change in coldness of air if so compressor needs changed out.

 

Another thing to check is that your radiator fans are working properly and your radiator coolant level is correct. If the engine starts to get too hot, the AC will cut out. (This will also happen if there was front end damage and the fans were installed in reverse.) When you are driving at 50MPH the outside air is providing the cooling to the radiator. When you are in traffic, the cooling is dependent on the fans. I think that is your problem, not the A/C itself. Also, you can't depend on the Check Engine Light to tell you this. The A/C will cut out way before the engine temperature is high enough to light up the CEL.

So, turn on your car and open the hood. Wait for the fans to kick in. If they don't it could be the relay or a sensor that turns the fans on or off. If you has front end work done, and the fans do kick in, and the air is blowing toward you, they put them in in reverse.

Either way, it sounds like there is something going on with your engine coolant system that is affecting your A/C.

 

AC is always running on electricity. AC amplifier controls the AC. It’s unlikely that some fault with AC amplifier (except the fan controlling circuit) would cause AC power to be dependent of vehicle speed.

 

If it's cooling better at high speeds, maybe the fans aren't working properly? They come into play more at low speeds and/or stopped.

 

easy to check the fans. when the car is hot and the a/c is running, open the hood, listen for the fans running and stick your hand behind the fans to feel them blowing.

 

Our 147K mi 2006 Prius doesn't have AC when car is sitting hot and battery charge indicates low. It seems to work fine in cooler temps. Gauges read ~30psi low side and 190psi on the high, which according to a gen 3 service document that is about right. The condenser looks clean and the fans are running. When 81 deg outside the ducts are below 40 deg.

It seems to have something to do with the battery charge level being low and only when hot inside the car. There are no fault codes and the battery modules all read almost exactly the same with diagnostic software reading the OBDII port.