My 2013 Prius (150,500 miles) is having issues with poor A/C performance so after checking for bubbles in the sight glass, I moved on to using manifold gauges. The 2010 Service Manual gives information on how to INSPECT REFRIGERANT PRESSURE WITH MANIFOLD GAUGE SET and the first test condition is "Temperature at the air inlet with the switch set at RECIRC is 30 to 35°C (86 to 95°F)." This may sound like a stupid question (it wouldn't be my first) but what air inlet is it referring to and how would it be controlled to be between 86 and 95F? The other thing that I thought strange is that the third test condtion is "The temperature control dial position is at "COOL"." I don't have a temperature control DIAL and the digital display does not show COOL but I used the LO setting. Would this perhaps indicate that these instructions were copied from an earlier Toyota model, maybe not even a Prius? Therre's no mention of whether the Power button should be set so that Ready is displayed so I just had the A/C running on battery. Unfortunately, the only pressure tables shown are for normal operation but it would have been helpful if they had also included pressure ranges for the various fault situations, instead of just gauge images. Mine both showed around 70psi so, it looks like my refrigerant level is low. Initial tests with a halogen leak detector show that both schrader valves are leaking slightly. At least, when I remove the caps, the detector goes nuts then stops beeping. However, if I try it with the compressor running and the caps off, it doesn't indicate but after running with the caps on for 10 minutes or so, it beeps again when they are removed. My theory is that they are not leaking very much but enough to accumulate under the caps and trigger the detector when opened. I checked for DTC's using the Auto and Recirc buttons and it showed 00. I also hooked up Techstream and again it showed no codes. The compressor speeds were all just a couple of revs short of target, at the various settings so I'm hoping that there are no other problems. I plan on taking it to a local shop to have the refrigerant removed and hopefully, they can do that without removing any of the ND-11. I'll replace the valve cores with a smidgen of Nylog Blue to ensure a good seal, evacuate and recharge by weight. One good thing is that it has started to cool down here in Florida but there are still some days when A/C can make a difference. I plan to replace the car sometime in early 2026 so maybe this will keep us comfortable until then.
Don't know for sure, but you might be able to use a regular tire valve core tool to tighten up the cores in the AC low and high pressure Shrader valves. Those valves are larger than regular tire valves, so maybe not. Or a special AC valve tool maybe. You probably already know about using a manifold pressure set that has been used in other AC equipment and will contaminate the special ND-11 oil. The blinking 00 at the end of the diagnostic means no malfunctions detected. I used the same diagnostic to determine a seized compressor on my Gen III. The air inlet they mention is the extension from the evaporator HVAC blower box under the dashboard where you change the cabin air filter (behind the glove box) to the external port in front of the windshield and inside the windshield wiper assembly box. Just make sure it is set to outside air (HVAC set to external intake not recirculate) and turn the cabin temperature indicator all the way down so the compressor runs continuously. Any loss of refrigant indicates a leak somewhere. The HVAC system doesn't "use" refrigant as some people might say. There are special UV dyes that can show where leaks are. When getting the system recharged, after identifying the leak(s), the vacuum drawdown will remove all refrigant, any water/air, and most of the ND-11 oil. Make sure your local shop knows about Prius HVAC and the special instructions associated with that system. Good luck. Edit: It appears that the inlet air in this case is interior air with system set to recirculate. Making sure it is warm though is required to keep the compressor running through the test.
The switch is set at RECIRC, so the air inlet is the one behind the glove box, where recirc air from the cabin enters the blower box. You don't have any easy way to control it in that temperature range; they're just telling you the pressures they are giving are appropriate for when the inlet air is roughly that temperature, and it's sort of a not-unreasonable temperature to expect when people are wanting to use A/C. If this car is a gen 3 then its A/C compressor is high-voltage electric and only runs in READY. If the car was not READY, you might have had the A/C blower running on (the 12-volt) battery, but you didn't have the A/C running.
thanks for your response. I did initially think to just tighten up the existing valve cores, as the manifold gauge set I have includes a couple of valve tools. However, that leaves the problem of insufficient R134a remaining in the system and as you probably are aware, it is important not to overfill when recharging. That's why I intend to have the recovery done and recharge by weight. The manifold set is brand new, as is my vacuum pump so no concern about contamination. Thanks for the info regarding the A/C air intake. I did know about the external vents but ruled that out as the Toyota instructions say to set the switch to RECIRC, which would mean that no or minimal airflow would be entering from outside. It's interesting that you say to set for external air intake but again, how would I be able to regulate the intake temperature to be between 86F and 95F, unless I rig up some kind of heater? I do have straight U/V dye but the cheapo injector I have was also used a few times to inject a different mixture of PAG oil and dye so I'll probably have to invest in a better injector.
