AC Works only when it wants to.

I would try some diagnostic tests.

When it DOES NOT WORK....

1. Will raising/lowering the temperature setting make it kick on?

2. Does the fan speed respond when adjusted manually?

I'm not an expert, but if adjusting the temperature makes it turn on, I'd be puzzled as my initial guess is that your cabin temperature sensor is buggered or failing as the AC responds when the setting is outside the range of the detected temperature.

If the fan won't respond manually, odds are something is wrong with the blower or relay setup that assigns fan speed (I had a problem a few years back on another vehicle, and it was a shorted wire(s) on the harness going to the blower).

Good luck. Anyone have a flowchart for diagnosing the AC system?

 

have you checked for trouble codes?

 

yeah, i'm not sure either.

 

Does pressing buttons on the AC get a response on the LCD display or do appropriate LEDs light up?

If not, perhaps some connector for the buttons is working loose and the default setting is OFF.

 

Blower motor could be going out. This happened to me on my Corolla every few years it seemed like. When it would go out it would do this type of intermittent behavior. I could sometimes start it by hitting the bottom of the glove box a couple times.

 

The rattling noise was also a symptom of the blower motor for me. As far as the heat question I am not actually sure how that works. This always happened to me (of course) in the middle of the summer, which is like 110 here in Dallas so I don't know that I ever tried the heater. The good news is that the blower motor should be much cheaper to replace than the compressor or some other parts of the A/C

 

Very easy DIY if this is the problem.

 

Blower motor is common and easy replacement. If no air from vents then that's likely it.


iPhone ?

 

And I don't know if this would happen so soon, but there can be an obstruction...if something built a nest in the blower motor housing. Removing the obstruction would fix the problem.

 

Does anyone know what to do if it IS blowing air from the outside? Here's what's going on for me: When I try to turn on the AC, the fan works, but I can't get cold air unless it's cold outside. And the display above the AC button says "Outside" instead of "AC," no matter what buttons I push. I've tried every combination. The AC button itself lights up with that little green light, but the display doesn't change. I've already had a new condenser and new freon put in, and I just noticed the display today. Somehow the button is no longer connected to whatever makes the AC work. I have a 2010 Prius. Any ideas? When you mentioned "whatever the button connects to," what DOES it connect to?

 

Enjoyed the video. Nice to see someone who knows basic electrical wiring. Was taught in auto mechanics school that a car is wired backwards. The body is hot and all the little wires grounds(yes odd Prius is using AC schema for wiring). Not sure that was for all vehicles. Do newer vehicles do that? Or is that ancient data from the civil war.
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After reading several sites I am sure I am totally confused. Must be a force field of sorts.

 

I'm not sure I'd buy that explanation, but it's true that some circuits in some cars are wired such that one terminal of certain electrical components is connected to the "hot" (non-ground, i.e., positive) polarity even when turned off. To turn such a component on, a switch connects the other terminal of the component to the car body (ground, i.e., negative). That might seem sorta "backwards."