2009 Prius. As we passed 100F here in Texas, I really noticed the AC isn't always working. Not sure how bad for how long. Sight glass foamy. Cabin air filter changed a year or so ago, not dusty environment, should be fine. Both fans running in front. Hooked it up to gauges. Read low/low, added straight R134a. A bit over 12 oz and eventually I got 40/310 at 95F ambient (might be closer to 100F), but I was seeing some really high pressures intermittently while filling. I thought I was overfilling although I'm looking at the chart for the ambient temp range and I don't know why I was thinking that. Sight glass went clear. Vent temp got down to 45F. Vent is quite cold, no bubbles in sight glass, so it seems good. However, in use the next day at 102F and in the sun, the AC ran at first but then stops working entirely after a minute. Looks like it won't come back unless the vehicle is left off for a bit. Torque app shows no error codes. Not sure if it was dropping out before vs just running poorly, but it's definitely not working right now. I was drenched in sweat after driving a couple of miles for groceries. I did leave the gauges attached while the engine was off for a bit, and then watched it start up. It got high, then high dropped and low rose like the compressor was dropping out, but in the driveway the pulsing stopped after a minute or so and I got stable, normal pressures. Is there an overpressure switch I might be tripping? Maybe a combination of slight overfill combined with astronomically high temps? Does the Prius compressor have a common failure mode where it just drops out? I know these are unusual since they're driven by high voltage. Additionally, the next day, I got red-triangle-of-death followed by immediate stoppage. Restarted a few min later. After diagnosis I'm thinking the fuel pump is going bad. Went on grocery run watching the hybrid display, the engine stayed on, battery mid-range, no RToD, but lost the AC after the first minute or so. Will do the fuel pump ASAP, but I don't think this is related.
I've never seen a steady 40 on the low side of my Prius electric compressors yet If I try to get 40 here in North Carolina without paying attention to the gauges and what have you when I get right near 40 38 PSI etc the compressor that's in my car starts to lock up I can hear it like the belt squealing but there's no belt and the compressor will stop If I let gas out just a little it runs impeccably up to about 34 PSI and I mean it's ice cold so I don't try to shoot for the 40 now in my Corolla with a belt compressor I have to have 40 PSI on the low side to be making cold well and everything to be copesthetic and happy but in the Prius or the electric compressor vehicles I have not been able to get that 40 PSI on the low side steady. And it might be also because these inverter compressors can ramp up and down while you're standing there adding the gas You may not notice it but I believe it is a thing so getting that steady 40 on the low side sitting there in the driveway doing your normal air conditioning stuff It seemed to be quite tricky so I don't even attempt it I have like 30ish I'm not sure what the high side is I don't hook up the high side gauge that often because there's not many problems with these to be honest about it and yes there is a pressure switch it's right there on that block with your site glass wires going to it etc I think it is built into that line you can't change it It doesn't unscrew like it looks like it does it's welded to the aluminum.
It's a mistake to charge a Gen 2 AC system by pressures, so there's always a chance it's very overcharged. There's also the possibility that your inverter is getting warm and cutting power off to the AC compressor. Verify the inverter cooling water pump is functioning properly. It's a relatively common failure point.
Please retrieve the obd2 code(s) with an appropriate scanner, then post them in this thread for additional guidance.
If you don't have a scanner (or you have a scanner that's inappropriate. for shame), you should also be able to get HVAC codes by turning the car on while holding the AUTO and FRESH/RECIRC buttons. Look for two-digit codes on the MFD, after it finishes the everything-flashing business. For the HVAC codes, I think there's a pretty simple mapping from those two-digit codes to the trouble codes you would see on a scanner (don't assume this generalizes to codes for other systems): a two-digit HVAC code xy generally represents the DTC B14xy.
