The AC on my wife's 2011 Toyota Sienna is not blowing cold. It has had intermittent issues like this in the past and was low on freon. I've had to add freon twice in about 1.5yrs. I added a can about 2 weeks ago and low pressure side was 45 after the can. I didn't check high side. It was about 95 outside. About a week ago we were in traffic and it was not cooling. It finally started to cool down. Today it stopped cooling again. It was 108 outside and low side pressure was about 50 and high side was 160. Compressor running but blowing hot air and lines not condensating. Anyone know what would cause the low side pressure to be normal and high side to be low. Bad compressor expansion valve? Thanks

 

 

Things go bad in the ac system for three things and any of them or a combination of can be present in your system. Fault in the wiring (loose connections or corrosion from oxidation and moisture), a leak, and/or a restriction.

I cant speak to your pressures but I have a reference link on my laptop, so stay tuned.

Tell me you're in the southwest. Those temps are blazing.

 

http://www.aa1car.com/library/ac98.htm

I doubt your compressor is going bad, unless you've ruled out leaks and restrictions. You could test it by applying power to it directly from the battery with testing leads (gotta be safe about doing it). You could also jump the low pressure switch, but if it doesn't engage, doesn't necessarily mean its not good as it could mean a possible bad switch. I should also mention that testing the compressor is risky for the part itself, because running if dry (refrigerant has oil) can cause damage, so avoid prolonged running.

Usually the pressures are due to leaks or restrictions in the system. This is likely because you've refilled the system twice already. So while leak detection with dye products can be one method, or listening for any hissing noises along the lines, pinpointing exactly where in the enclosed system for either the leak or restriction is extremely difficult without pulling out ALL the major pieces and inspecting them or replacing them. Often times, story after story, one part is replaced (or a few), but the problem resurfaces later, because one component was not.

It is more than measuring pressures and topping off with refrigerant, unfortunately, but its definitely a good start. If you're prepared to face it, you would need special tools (that are available for us DIY folk) in order to evacuate the system and open it all up.

Hope that sheds some light and helps in your decision. I highly recommend not replacing only a few components. Likely, the best solution is replacing all, unless you pull them out and inspect.

Of course there is the shop. But don't let them replace just a few parts either. Let them do the whole system and be done with the frustrations of repeat troubleshooting, unless they can tell you for sure the suspected components are in fact ok. Dont take a guess as a confirmation.