I have a 2006 Legacy 2.5i and the other day it was really hot and humid (90+ degrees).  I got in my car in the middle of the day and turned on the AC and it never got cool.  It had been not cooling so well at idle, but when I accelerate it would cool back down.  This was the first time it just didn't work at all.  I could hear the compressor trying to kick in and then kick back out.   

 

I just thought it was low on refrigerant, so I went to Walmart and bought the can with the gauge and was going to top it off myself.  Well, when I put the gauge on with the compressor running with AC on high, it's showing between 40-45 on the gauge which is labeled "Alert."    Is this thing overcharged and the high pressure switch is kicking it out?   Remembering from my physics class gas expands when it's heated, so it makes sense the pressure would go higher on the hottest day so far this year. 

 

When I got off work the same day and drove home, it worked like normal.  It was only when it was outrageously hot outside and inside the car at lunchtime.  

 

Is it as simple as being overcharged or is there something else that could be wrong?   

 

The outside temp when I checked the pressure was around 80 and the AC was cooling properly at that time.

Edited June 18, 201411 yr by huffman142

When its really hot out these systems can have a hard time cooling the car, especially if its been sitting in the sun for several hours.

The newer cars do generally run a lower pressure than that, which could mean it is overcharged. I would have to look up the recommended pressure to be sure.

 

Are you the original owner of the car? Have you ever had the AC system serviced or charged

 

The closest manual I have is for 2005, but the system should be the same as your 06. Pressure should be between 18-28 psi at 86-95 degrees outside temp.

Now the guages on those cans are not exactly what I would call accurate, but I can't imagine its THAT far off. The only way you get overcharged though is if someone tried to charge it in the past and overfilled it. The R-134 systems generally start to leak around 5-7 years old and need to be re-charged. If you've only owned the car for a few months, then its likely the previous owner tried to recharge it.

Edited June 18, 201411 yr by Fairtax4me

I've own the car a year.  I didn't notice it last year, but I didn't drive it much last summer and it was kept in a garage then so it never got the extreme heat built up from sitting in the sun for hours.  That's the only time it's not worked at all, but it did come back on within 10 minutes and worked fine after that.  I was sitting in traffic for the first few miles when it wasn't working.  After getting some higher rpms, it cooled down.  Maybe just expect that at such extremes?  It was really miserable that day.  Not just normal summer heat.  It's worked fine since then.  

 

Thanks for the input.

Both fans running? No fan can cause high pressure on both sides.

does the car idle weak at all?

to test - at idle turn the wheel hard left and right over and over again - until someone dials 911. look for any hesitation, stumbling, or lights coming on the dash, weak idle, etc. 

 

if so - clean the throttle body and idle control thingamabob on the throttle.

 

fix the idle - get a strong idle - and you'll fix the AC issue.  or at least i've done that once on a friend legacy the same vintage as yours.