AC starts off warm but gradually gets colder after several minutes of driving

Is this what the vehicle set in the manual low mode Vince blowing out the forward facing recirculation mode not auto and this is your setup 1 to 2 minutes to wait I mean yeah for the car to start stabilizing maybe I mean if you're starting a car and it's $140° in the car it's going to take a few minutes for you to get the temperature down get the car stabilized interior wise etc. But if you can compare it directly to your other car which is parked right next to it in the same heat etc then you may have something and what happens if you look in the sight glass that's over there near where the wires go to the skinnier hose to the sensor Do you see bubbles when the compressor started and then they vanish to clear?

 

Doesn't sound like anything is wrong other than you're impatient. I've never once driven in a car that instantly had cold air... It takes a while... And the hotter the weather, the longer it takes.

 

The hybrid system controls how much power goes to the AC... So if you have 1) failing hybrid battery or 2) failed inverter coolant pump (once the inverter is hot) you get a lower AC setting from the computers. You can avoid that 1st hassle by upgrading to the most advanced battery chemistry available: https://projectlithium.com/?ref=9qLPw rather than the max profit junk battery chemistry that Toyota uses even though it's been outdated for almost 40 years.

Beyond those types of "normal" the first step in diagnosis is replacing or removing cabin air filter... The next step is running both cars side by side with windows rolled up and AC on full blast and a couple thermometers to see if both cars reach close to the same temperature.

If a problem is confirmed then you'll need a shop with an expensive piece of equipment to extract the refrigerant and lubricant to measure it by weight and if it's low add more. And if super low they'll likely add a dye to search for leaks.

If you want to learn everything possible about Prius AC simply check out all the posts from @lech auto air conditionin That dude is a hard working genius who knows it all.

 

Your poorly performing car is either under or overcharged. Over if someone has tried to “fix” it with a big Walmart can of r134a. Under if it has a leak. Look got condenser leaks. Solution or diagnostic is largely the same, recover, vacuum and weigh in the nameplate volume of r134a with no oil or sealer.

 

Agreed. My advice is largely the same.

If a problem is confirmed then you'll need a shop with an A/C machine that will recover the refrigerant and also measure the recovered refrigerant by weight. If the refrigerant is low the system will need to be checked for leaks by doing a vacuum test (the service port valves should be changed out for new ones while the system is empty to eliminate a leak there). If leaks are suspected because the system will not hold a vacuum, then the source of the leak needs to be located and repaired. Usually, UV-sensitive dye is added to help find leaks Once no leaks are confirmed, a precise quantity of refrigerant by weight (specified on the hood sticker) is added. Then you're good to go if the vent temperature is within spec, i. e. ~ 42ºF (5-6ºC).

 

So when you look at your sight glass you will be able to get an idea whether you are under charged at running or overcharged If you have an assistant start the air conditioning while you're staring at the sight glass and you see bubbles for literally seconds and then it clears right up and you never see a thing again until you turn it off and restart You're probably overcharged. If you do it again and you turn it on and you see one bubble go by and then it clears up immediately probably overcharged If you start it up and you see bubbles for a few seconds and they slowly slow down and then predominantly go away you're probably closer to the charge being correct. Obviously the only way to know this is to vacuum the system down recover all the gas making sure there's no leaks replace whatever o-rings you should while you're at it with the most modern compound for the o-rings and then reinsert 1.3 lb of gas into the system modern shops can meet her this by weight and electronics they can drop it all at once Bam it's in there That's the end of it whatever else is going on is with the car not the amount of refrigerant that was just pushed into the system and then you can go from there. But that gets expensive I don't even know what that would cost in my area right now If I took it to the relatively decent air conditioning place around the corner it's probably going to be $250 to drop the car off and just do removal leak checking and if no leaks are found replacing the exact amount right of gas close to 300 pops I can do that in my yard for the cost of the two cans of gas I'm only going to use one can and 2/10 out of the other I can get it close enough for my liking 3/10 instead of 2/10 is not going to make much of a difference but adding the whole other half a can or so would not be good so you can get it very close and then it should work within specifications All of mine do and none of mine have been sent anywhere.

 

Yes I'm imagining if you want to pay for that service they'll pull that gas out of there Make sure there's no leaks with a vacuum test etc then meet her in the exact amount of gas that's in their software for the car or on the label on the yellow sticker under the hood either way If one doesn't want to pay that some shops will just top your system off to make the bubbles just about go away etc and you'll have your cooling properly out the vents and all that and pay them and off you go so you could have done it in driveway but better you don't.. let somebody that has somewhat of a clue of what's going on handle it with they mess it up they can pay you or fix it or whatever so that's a good move if you don't have tools gauges stuff like that It's a smart move The blue car is probably charged up right when they are you'll see bubbles on the startup only You have to be looking at the sight glass the minute the compressor kicks in or the person in the car turns it on You can't turn it on and run out and look it'll be clear It just has a few bubbles go flying by when the compressor kicks on and what's happening when the compressor initially starts up his the compressor starting up forms the high and low sides on the compressor in the system what have you when the system is at rest and you take a reading on both the high and the low sides there be the same PSI because there is no high and low side when the compressor is not running.