AC not very cold at idle, great while driving

[Jonas]

Hi everyone. I have a 2009 Pontiac Vibe GT with 190k miles. As the title states, my AC temps creep up at idle, and go back down once I've been driving for a while. I'm leaning toward it being an airflow issue since it is properly charged and when I spray the condenser with water, the temperature at the vents quickly drops about 5-6 degrees. My car has two cooling fans and my best guess at the moment is that one of them is not spinning fast enough or going into "high" mode-possibly due to a bad relay. I've cleaned the condenser which made a marginal difference. Even when it's 70 and raining like it is today, the temp at the vents will rise as much as 12 degrees if I sit still long enough. I'd love for anyone to help me troubleshoot this and I think (hope) it's something simple since my mechanic verified the air conditioner is charged/working well, just not very cold at idle. He doesn't know why either. Thanks in advance,
~Jonas

[tbirdtbird]

Get your fans working properly and get back to us. The fans should be on at idle, perhaps all the time, I am not familiar with details of that exact car.

Actual vent temps at idle and when on the road would also be helpful

Is the condenser almost too hot to touch at idle

[Tim]

As well as what was mentioned. Find someone to run a scan and get the error codes.

[Jonas]

Both fans are turning when the AC is on. It's difficult to tell, because I can only hear the fan(s) on high speed, but as soon as I open the hood to look they die back down. I'm just speculating that the condenser fan is weak and/or faulty since my problem is likely air-flow related. I thought it could be engine speed related, so I held the RPMs at 1500-1800 for a couple of minutes in park and the vent (center dash with a probe thermometer) dropped 1, maybe 2 degrees.

The following data is based on a recent 97 degree, sunny day: Center vent blowing 55+ degrees while stuck in traffic-vent fan always on medium high, max recirculate always on. On the interstate, it got down as low as 46 degrees. It's worst when I'm stopped in drive, like at a light. When I'm parked and idling it's about 2 degrees cooler. Not so much driving fast, but driving non stop for long enough, the temp would consistently drop to 48 and below. Cabin temp (thermometer in cup holder) was around 85 degrees.

The condenser was not dangerously, but uncomfortably hot to the touch after the car had been running only a minute or two with the AC on. As mentioned, a brief spray of water quickly and drastically drops the vent temperature.

There are no trouble codes on my basic OBD reader, but that probably doesn't mean much.

[tbirdtbird]

as soon as I open the hood to look they die back down. I'm just speculating that the condenser fan is weak and/or faulty since my problem is likely air-flow related.

It would be nice to determine why that happens.

Not so much driving fast, but driving non stop for long enough, the temp would consistently drop to 48 and below

for long enough

Not sure how much below 48° you mean when you have been on a long run. Seems like it takes a while to get as cold as it is gonna get.
What area of the country I wonder

The condenser is supposed to get pretty hot, that tells us it is doing its job.
Agree with Tim to get scan codes. I have had to replace fans due to weakness.

I am not certain a low charge can be ruled out, either

Did this car ever cool properly for you?

[Jonas]

I can't really tell what's going on with the fans-they both spin, though. It was not hot today, and I suppose opening the hood cools off the engine so they die down. Maybe they're just weak-they are 13 years old.

48 degrees was as cold as the vents ever got on that 97 degree day while driving around town (other than a 4 mile interstate run where they reached 46). I live in southern Kentucky and it's usually humid as well. This was all with recirculate on.

If I'm driving non-stop the air will get as cold as it gets in about 3-5 minutes.

The AC was charged by weight. Max fill is 16.46 oz and I have ~16 oz in there. This was done 3 days ago.

I vaguely remember wanting the AC to be colder last summer when I bought the car. I don't think it bothered me too much, partly because I was enamored with my new car and my last car didn't have AC.

I know AC performance is somewhat ambient temperature dependent, but if it is below 90 or cloudy/late in the day, the AC is at least 6 degrees colder on average and I'm quite comfortable in the car. However, the temperature swing between driving and idling is still 8-10 degrees.

How would I go about scanning for AC codes?

Thanks. I hadn't considered most of these ideas.

[Jonas]

Thanks, Al9. Yes, it's a control valve operated compressor (Four Seasons Nipposndenso type) I will give a listen under the dash and report back.

[tbirdtbird]

"The AC was charged by weight. Max fill is 16.46 oz and I have ~16 oz in there."

Did a shop do this?
Are you doing any of your own work?
If a shop, did they recover, evacuate, and then weigh the charge in?

[JohnHere]

The AC was charged by weight. Max fill is 16.46 oz and I have ~16 oz in there. This was done 3 days ago.

All of my references say 23 ounces of R-134a, so it might be undercharged. Is there an engine-compartment decal that specifies 16.46 ounces? If so, the decal would take precedence.

Also, take a close look at the condenser with a strong light. Corrosion, if it's present, could be compromising heat transfer between the fins and tubes.

[Jonas]

It does seem like a control valve issue, but the compressor was purchased new about 2 months ago, so I hope not.

The decal under the hood says min 0.90, max 1.04 (16.46 oz) charge. I evacuated, vacuumed, and charged it by weight myself-16 oz.

I've seen 23 oz capacity before too, but I went with the hood sticker. However, I read somewhere that the sticker can be wrong -someone's Camaro (also GM) hood sticker said the AC holds 9 oz which wasn't even close. There all also misprints in the manual, like wrong transmission fluid and wrong coolant.

I will look/listen closely to the compressor and under the dash and report back.