Gen 3 A/C

Pressing Auto will not turn on the A/C. There is a separate button for that with with a green indicatorlight. You need to turn that on manually for the A/C to work.
If it doesn't work when you press the A/C button there is likely a problem. Maybe a blown fuse.

 

you can run a/c either in auto or manually. for manual, the a/c button light should come on if you turn the fan on and press it. keep the temp on 'low'.
for auto, hit the auto button and set your desired temperature. when the compressor is on, the a/c light should come on.
if it is not cooling, you will need further diagnosis.

 

Yeah that's the way our Canadian 2010 works. Usually, the AC (North American definition of "AC", a system with active cooling) requires the AC button to be pushed, and it'll be lit, to confirm. Pushing the "Auto" button does not activate AC.

Our previous Civic Hybrid was the other way 'round: push it's "Auto" button, it invariably did activate AC, and I was forever pushing Auto, and immediately thereafter switching AC off. Bit of a pain.

With the Prius (at least our 2010 Canadian model), there is one additional wrinkle (observed with Scan Guage): if you push Auto, then override mode to to Heat/Defog, as highlighted:



Then the AC will sometimes run, even though the AC button will stay unlit.

The other way to activate AC indirectly, is by pushing the front windshield defog button:



This will for sure activate AC, but it's obvious, and the AC button will be lit. Fan speed also ramps way up. I like to call that "hell's-a-popping" mode.

Controls aside, it could also be possible the AC system is getting low on fluid. There's an under-the-hood "sight glass", basically a little window allowing you to observe the fluid while the system runs.



If the system is properly charged, when the AC compressor is running (both fans at the back of radiator will be running) you should see just a few fine bubbles whizzing by. When the compressor stops (fans will stop as well) you might see a momentary swirl of bubbles.

I'll attach the Repair Manual page with the sight glass info.

 

The ac light turns on when you hit auto. If it’s not turned on, I would check for the fuse or relay for the ac compressor.I haven’t checked but it’s one of those. I’ll further check when I’m home.

 

I have never noticed my A/C light turn on when I hit auto. I've always seen it stay reliably selected or deselected based on what I last did with the A/C button, which is just the way I like it. As Mendel points out, defrost mode can force it on, to help dry the air.

Am I missing something, or is my 2010 broken (I don't think so), or did they change the behavior with the 2012 refresh?

-Chap

 

Not sure, but I tested with the ac button turned off and ac not running, and I hit the auto button and the ac light came on with blower motor on high. Maybe they updated in the 2012 version? Lol not sure, I’ll have to look at the wiring diagram to be sure.

 

I don't believe the wiring diagram will shed any light on the internal programming of the HVAC control (though it will identify the wires connecting to it).

But I would check in the manual for where the customizable (by Techstream, Carista, etc.) settings for the car are. IIRC, some of them are indeed for the HVAC.

I made a point just this evening of trying mine; 82 F outside, I pressed auto multiple times, adjusted the temp setting all the way to LO, etc., and the car never took it upon itself to decide I really wanted A/C if I hadn't said so.

But if that's a customizable behavior, that could explain how we see different things.

-Chap

 

Yeah it’s possible, kinda weird... probably a customizable setting. But back to the original poster, their a/c light doesn’t even turn on, could be a fuse, relay or just low on R123.

 

R134a, but anyway. Techstream would probably make short work of the diagnosis (which could be anything as simple as a dirty contact under the A/C button). I'm pretty sure the live data list can show you things like which buttons are being pressed, not to mention plenty of other status, so you can see what signals are getting through.

-Chap

 

Whoops. Brain fart lol R134a. I haven’t messed with techstream even though I got the mini VCI. All my stuffs in a mess as of right now.

 

Moving will do that.

You ever want to mess with Techstream, I’ve got a working setup.

Maybe that’s how we can “randomly” meet up.

 

Could well be the interplay of Auto button and AC activation changed at some point, say at the 2012 refresh.

 

Never heard back from the OP, wonder if she got it fixed?

 

Mine does the same.

 

Just chattin' among ourselves: I've got an AC appointment for ours, for next week. I've been noticing the AC's working, but not that great. Also, last fall I watched the sight glass while it was running, and it was definitely far from clear: when the fans were running (AC compressor running, there was a "flurry" going by, I'd say 50/50 bubbles and fluid.

We don't use AC regularly, more so in winter in the rain than in summer. Also, the car's build date was August 2009, and we bought it (new, with 10~20 kms on the odo) in November 2010. It could be some seals are drying out, with this history.

The service writer told me all sorts of reassuring things, about evacuating and then pressure testing the system, and then doing testing with some sort of infra-red vision, to check for leaks. Hopefully will be sorted.

 

Here in Finland it is told that one should change(get serviced) AC system every two years.
Reason been that system gathers water in for example what causes problems. And also if you dont use AC, you should turn it on at least once per month to get AC fluids circulated and sealings lubricated.

AC system flush, vacuum test and fill up here is around 75€.

 

I noticed yesterday, when it was well over 90° here that ours felt pretty wimpy. I need to check mine now that @Mendel Leisk provided the handy instructions. BTW, Mendel, is there another page to that? One row in the table says, "refer to 5 and 6," but there's no 6. Thanks!!

 

They're telling me around $150 (CDN). I see that's currently $97 euros. Not too far off. They do caution, that could go up, if they find a leak and have to start replacing things. Oh well.

Attached a more complete version. This is something I'd leave to the pros myself, but an interesting read.