A/C...How cold should it get at idle? What is Normal?

[hoovie87]

I have noticed on our 2013 Sonic LT that the A/C doesn't get very cold when idling and on high. It is about 88 degrees here today for the first time this year. I turned the A/C on high with all the doors open on recirculate and read in the vent about a 25 degrees cooler air temperature from intake to outlet on the A/C, but it doesn't cool the car all that much. If I rev the car a little, it cools down better. The compressor stays on as it should, coolant is good, and the radiator fan is running well.

Is this normal in hot weather for this car?

Seems like it would stink if I were in stop and go traffic. At idle, the coolest the interior would get was 81 degrees at idle.

Regards,
David

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[hoovie87]

Anyone think it needs a charge or something?

Regards,
David

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[mitdr774]

When I was in the dealer the standard we were given was 20* below ambient on setting one or two when measured 6" in on the left center vent. The higher the blower speed the less of a difference from ambient you will see. Recirc is pointless if you have the doors open or windows down.

 

[ChrisJ]

When I was in the dealer the standard we were given was 20* below ambient on setting one or two when measured 6" in on the left center vent. The higher the blower speed the less of a difference from ambient you will see. Recirc is pointless if you have the doors open or windows down.

That's pretty lame.

When I converted to R134A and rebuilt my 1992 pickups AC I was able to do 36F when it was above 90F out sitting still with blower on high. That's a 54 degree difference. To be honest, I almost want to say the picture I have of it showing 36F was taken when it was 94F or 95F out but I can't remember anymore, just that it was above 90.

Now I admit, I did some tweaking to the system, ok, a lot of tweaking, but I'd still expect better from any system than 70F, that'd piss me off.


I agree with you about doors open etc, but I always tell people to run recirculate whenever it's above 80F as it not only reduces vent temperatures, but greatly reduces head pressure. Sitting in traffic without recirculate on if it's above 90F out produces scary high head pressures.

 

[ChrisJ]

Anyone think it needs a charge or something?

Regards,
David

Sent from my Samsung Galaxy Note II

No one can answer this via a forum, though many may try.
Only a good technician that knows how the system should function and can observe it will be able to answer that. It's also not as simple as "checking pressures".

For me, the Sonic performs best on the highway with recirculate on. Stuck in traffic it may be kinda mediocre by my standards but it's not bad.


Basically, if you feel it's performing subpar and are using recirculate then you need to take it to a good shop or dealer. Also, the only real way to get an exact charge in the system is to evacuate it and then charge it with the exact weight of refrigerant called for by the system. "Topping off" works, but is far from perfect.

Just remembered something I had learned a while back.
Is your car a manual? If so, try running a gear lower when it's really hot out. This will spin the compressor faster and will show a very noticeable improvement.
I have a 6 speed manual and will often run a gear lower to keep the engine spinning around 2000-2500. On really hot days my usual 1200-1500 just isn't enough.

I don't know for sure, but I would use caution about holding it at higher rpms when stuck in traffic. I wouldn't be surprised if you could cause the car to overheat. I only advise the 2000-2500 rpm trick when going down the road 20MPH or faster.

 

[hoovie87]

Recirculate and doors open so I could measure a consistent intake and outlet temperature. I figured that would have made sense to everyone. I was sitting in the driveway for the test.

Regards,
David

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[ChrisJ]

Recirculate and doors open so I could measure a consistent intake and outlet temperature. I figured that would have made sense to everyone. I was sitting in the driveway for the test.

Regards,
David

Sent from my Samsung Galaxy Note II

If you're trying to rapidly cool the car down and the interior is hotter than the outside keeping recirculate off and rolling the windows down, or having the doors open is best.

Pulls the cooler air in.

Other than that, not sure about your test. Most call for windows up, doors closed, recirculate on, temp control full cold, blower on high and engine at something like 1500rpm.

 

[mitdr774]

20* was just what were were told the standard was. I rarely came across a car that was close to 20* change. Most were a lot higher. Quite a few cars could drop the temp, 6" inside the left center vent on low, from 80* in the shop to mid 30's. A few would freeze the evap core.

 

[hoovie87]

Thanks everyone for the feedback!!!!!! I appreciate it a lot.

Regards,
David

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[hoovie87]

If you're trying to rapidly cool the car down and the interior is hotter than the outside keeping recirculate off and rolling the windows down, or having the doors open is best.

Pulls the cooler air in.

Other than that, not sure about your test. Most call for windows up, doors closed, recirculate on, temp control full cold, blower on high and engine at something like 1500rpm.

I didn't know how they did this for cars. I just did it like a home a/c test. Measure in and out temps to see if it helped everyone understand how cold it was getting.

Regards,
David

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[ChrisJ]

I didn't know how they did this for cars. I just did it like a home a/c test. Measure in and out temps to see if it helped everyone understand how cold it was getting.

Regards,
David

Sent from my Samsung Galaxy Note II

Try the following on a good hot day and let us know what you find.

Windows up, doors closed
recirculate on
full cold
fan #4 or highest setting
AC on
Thermometer in center vent

Let system run for 5 minutes or so idling.
After the first 5 minutes, raise the engine speed to 2000rpm and hold it there for a while and see what your temperature does. I think you'll find it drops substantially.

As for going down the road, on an 80-85F day I'd expect 40-42F vent temperatures on the Sonic with the blower on high, recirculate on and keeping the engine at 2000-2500rpm.

 

[hoovie87]

Okay, that answers my question. So it gets quite a bit colder when driving in this car...

Regards,
David

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[ChrisJ]

Okay, that answers my question. So it gets quite a bit colder when driving in this car...

Regards,
David

Sent from my Samsung Galaxy Note II

It should get a lot colder when going down the road, yes.
The only systems I knew of in cars that did fairly well sitting still were R12 systems. Specifically, 1970s GM though the 1980s did alright as well.

Every R134A system I've seen is mediocre at best idling and not moving.

 

[hoovie87]

O, ok. My Ram a/c still gets cold at idle, and a little colder when driving, but the sonic doesn't seem to get real cold until the engine is revved a little. Does the Sonic have a smaller compressor maybe? Since it is all about efficiency?

Regards,
David

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[ChrisJ]

O, ok. My Ram a/c still gets cold at idle, and a little colder when driving, but the sonic doesn't seem to get real cold until the engine is revved a little. Does the Sonic have a smaller compressor maybe? Since it is all about efficiency?

Regards,
David

Sent from my Samsung Galaxy Note II

Your ram has a much larger condenser, and likely a larger compressor as well. I'd also assume it has a clutch type belt driven fan?

The Sonic is designed around fuel economy and that means tiny everything. So yeah, what you said.

Best thing to do is on days when you feel it's just not enough, run a gear lower like I do. Most of the year I cruise on some roads @ 1200-1400 rpm but on those really hot days it's not enough for me so I go a gear lower to get the engine spinning faster.

 

[hoovie87]

Thanks!!!

Regards,
David

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[CheapFuneral]

That's pretty lame.



When I converted to R134A and rebuilt my 1992 pickups AC I was able to do 36F when it was above 90F out sitting still with blower on high. That's a 54 degree difference. To be honest, I almost want to say the picture I have of it showing 36F was taken when it was 94F or 95F out but I can't remember anymore, just that it was above 90.



Now I admit, I did some tweaking to the system, ok, a lot of tweaking, but I'd still expect better from any system than 70F, that'd piss me off.





I agree with you about doors open etc, but I always tell people to run recirculate whenever it's above 80F as it not only reduces vent temperatures, but greatly reduces head pressure. Sitting in traffic without recirculate on if it's above 90F out produces scary high head pressures.

I agree here. Last I heard before the vent should be around 40. If your a lot higher then I'd i would have it looked at. If I was under warranty I wouldn't even bother asking here I would take it to the dealer and have them check the ac. It's free anyway.


**** you auto correct!

 

[hoovie87]

Thanks!!

Regards,
David

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[CheapFuneral]

On a side note do you have tinted windows? I live in Florida so dealing with heat is a daily thing thru the year. Before my windows were tinted it felt like the ac couldn't catch up. Now I'm nice and cool in all conditions.


**** you auto correct!

 

[hoovie87]

Yea. They are somewhere in the 20 to 30% neighborhood. Pretty dark.

Regards,
David

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