Intermittent A/C - no codes. needs Han Solo

My guess is you would only find hints around here if it were more common for people to develop intermittent faults in their A/C.

As it is, from your description, your conclusion seems reasonable. Diagnosing for an intermittent loose connection is tedious, but the hints don't change much over the years. You fix yourself up with access to the wiring diagram (more info), figure out where the circuits are that could be involved, make a game plan for checking them (sometimes grabbing harnesses and connectors and shaking will give you clues), and follow the plan.

Is there a specific reason you don't think it's a problem at the compressor connector?

 

A copy of the service manual and Techstream software on an old windows laptop with a mini-VCI cable would help. First I would look the the diagnostic procedure to troubleshoot inoperative A/C - famaliarize yourself with how the system works. Then use Techstream to check all the ecu's for possible codes, and to look at relevant data - both when it is working and when it's not.

It could be all kinds of things such as the high pressure sensor, or evaporator temperature sensor, etc. So you have to see what "good" data is on your car then you can recognize what is wrong when it doesn't work.

Posted via the PriusChat mobile app.

 

Intermittent issues come in all shapes, sizes, locations, and reasons, so there's generally not much reason to think there will be "the" quick fix. The one thing that is constant among such problems is the way you diagnose them: get out the wiring diagram and a meter, work along the circuit from one point to the next, test, shake, repeat. Find what's causing your issue in your car and then fix that.

Usually, even if you do find a post that says "hey, I found the fix, totally solved the problem in my car!", it's just been posted by someone who had no reason to think about anything besides that one car's problem, and it's still not worth betting very much that your car's issue will turn out to have the exact same cause.

 

I'm having the same issue with a 2014 Prius V. AC was cutting in and out for two days and then magically healed itself right after I dropped it off for my mechanic. Yesterday, my mechanic said he could find nothing wrong and couldn't diagnose it because he was "chasing a ghost." I'm pretty sure it's a bad sensor, but have no idea which one. I've read on Gen 1's and Gen 2's that you could hold down auto and recirc buttons and get a code? Is there a way to do this on gen 3's? A code would definitely be helpful here, but the check engine light has not been on when the ac was down. My only clue is that when the ac was blowing warm air, the compressor and fan would only come on for 1 or two seconds at a time...almost like a sensor or connection was loose. When blowing cold air, the fan would stay on much longer before cycling off and the compressor never seemed to go off, even after 2 hours of driving.