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Discussion Starter #1 (Edited)
Hey everybody, I’m new here. I got a 2017 premium 5dr that I purchased in October of last year. It’s my first Subaru, and so far have only had some minor issues with it, like the radio glitches and such. Also, it’s got the manual climate control, which is probably important info for this.

I live in the northern part of the Sacramento Valley, and temperatures are in the upper 90s to low 100s most days in the summer. The AC in the impreza just does not seem to be cutting it.

I took it to my local dealership to get my first oil change @5000 miles a few days ago and had them look at the AC system because it’s been barely cooling on hot days. They reported back that it’s performing as it should, but my cabin air filter was dirty and could be causing the problem. So I had them put in a new air filter, no change. According to the invoice I was given, they measured the vent temp at 55 degrees which is considered within spec. They then evacuated the entire system, reporting that 1.5 lbs of refrigerant were evacuated, when system should be between 0.95 lbs and 1.10 lbs (again, according to the invoice paperwork from the dealer). To me, this says that I was right, the system was overcharged when I brought it in, but they said nothing was wrong with it, recharged the system, checked the pressures, and sent me on my way.

The AC blows fine and cold when outside temperature is below 85 degeees or so. When that’s the case, vent temp as measured by myself is down near 40 degrees when driving, and rises to about 50-55 when idling, depending on fan speed. As soon as the temperature gets above about 85-90, performance drops off dramatically. Vent temp at idle soars up to 65, and stays around 55 when driving or using lower fan speed.

I still think the system is overcharged, and here’s why. When I pop the hood and start the car with AC full blast on a hot hot day, the low side suction line going into the compressor immediately gets pretty cold, and starts sweating, but only for about 10-15 seconds. Then the suction line warms up to almost ambient again, and never gets cold again. All the while, the compressor never stops turning. Even on a relatively cool night, with AC running on the lowest possible fan speed, the compressor will not cycle off. Every other car I’ve had in the past cycled the AC on and off when the fan speed was low, and only stayed on continuously when cooling load demand was the highest.

Either way, there’s something fishy with how the low side suction line going into the compressor will get super cold when it first starts before warming back up again. Meanwhile, the high side line stays very hot to the touch, no matter what the low side feels like. The only way I can get the low side pipe to feel cold to the touch again is by turning the fan speed down super low, and even then it takes 5-10 minutes to really feel cold again.

I have a feeling the dealer ran their tests in the morning hours before it got hot, so they probably didn’t see any problems. But is 55 really all I can expect out of the vents when driving on the freeway on recirc? In the past, even at idle sitting in the hot direct sun, my 06 Mitsubishi would chill me to the bone. I’m considering picking up a set of gauges and testing the **** thing myself, but I’m not flush with cash at the moment so I’d rather not have to buy them if I don’t need them.

From my own research, it seems like it’s either still overcharged, or the compressor is bad. The car is less than 2 years old, so I doubt it’s the compressor, but I can’t say for sure. Maybe air in the lines somewhere? I looked for a sight glass but couldn’t find any on this model. Also couldn’t find any sort of manual throttle control that I can operate from the engine bay.

My last car was white, and my impreza is black, so I know that’s contributing to my discomfort, as well as the moonroof I didn’t use to have. In addition, I have yet to have any ceramic tint installed, which also usually helps with staying cool, but I still want colder vent temps.

Any suggestions? Anyone else not satisfied with their AC performance?

I read something about these models having variable output AC compressors, maybe that’s why it runs constantly without cycling. But again, I’ve got manual climate control with no internal cabin temp sensor so I don’t know how a variable compressor would be used in this setup.
 

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With variable output compressors the compressor does not have a clutch so it appears to run all the time. Something you should realize about AC systems, they do not make cold...they just transfer energy from one location, the cabin by absorbing energy to the evaporator behind the dash and sending the energy to the condenser in front of the radiator to be released to the outdoors. Since this is just a transfer process the system has a limited ability to transfer energy. With a really good system you will see a 30-35 degree F difference between interior and exterior temperatures. Also, the system pulls interior energy from everywhere...dashboard and instrument panel as well as interior air so if your car has been sitting in the sun it will take some time for the hot dashboard to equalize with the interior air temp.



Not what you want to hear but the system is probably performing normally. It is very easy to see if the system is under or overcharged...all the dealer has to do is put a set of AC gauges on the system. High readings on high and low side=overcharged. If high side has low pressure=undercharged. The service manual will have proper system pressures that can be adjusted for ambient pressures.
 

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Discussion Starter #4 (Edited)
I took a couple pics of the compressor and label. As for the whole clutch thing, it definitely has a clutch. I’ve watched it engage the AC, the compressor doesn’t spin unless the AC is on. When it’s on, it pretty much never stops, but it definitely has an electromagnetic clutch on it.

I know the system is simply moving heat from one area to another, and that usually it will only succeed in getting air about 40 degrees lower than inlet air. But the problem happens even on recirc, when the air starts out cold. The cabin temp can be 80, and the vent temp coming out will only be 65 on a hot day. It very well may be how this system was designed to perform, but it’s definitely not performing like the last car I had in the same heat. I would expect 65 to come out of the vents if it’s 105+ outside, and I’m sucking in outside air, but even if it’s recirculating cold air it struggles. The other reason I have suspicions is how it rapidly changes performance based on outdoor temp. I’m not exaggerating when I say the difference between 85 and 88 ambient temp translates to about a 15-20 degree jump in vent outlet temps. And since the low side pipe coming out of the passenger compartment in the engine bay barely feels cold when I’m experiencing this problem, it makes me thing the low side pressure is also higher than it should be. Isn’t it possible that the rise in outdoor temp could be causing the whole system to rise in pressure to a point it can’t create a big enough pressure difference?

I’m definitely no AC pro, but I still think there’s something strange about how it gets super cold for 15 seconds and then warms up almost to ambient, even after cooling fans come on.

As for the compressor, I am still wondering whether or not this really is a variable compressor at all. I didn’t think they would use different compressors for different trim levels, but models with auto climate control might have a different compressor. Anywho, take a look at the pics.


I’ll probably end up getting some ceramic tint installed to help out, that’ll definitely make a big difference rejecting some of the infrared from the sun.

I bought this car up in Seattle where I’m originally from, and I’m wondering if it’s possible that they charge systems differently depending on the climate they’re destined for? A long time ago my mom had a Toyota Highlander that was originally sold in Canada, and it had a totally different AC compressor than models from the states, because I assume you just don’t need a large compressor for Canadian summers.

Thanks for the replies!

Edit: looks like the model number for the compressor is a DENSO SCSA08H , the other numbers are other specifications I presume.
 

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Thanks for sharing that. My car has the same compressor, and it definitely is equipped with a typical clutch. That's not to say with certainty that the compressor isn't also variable displacement, but it is probably just a regular typical AC compressor.


I'm no AC expert either. Have you tried observing vent temps over time while driving on the freeway for say, 10-20 minutes?


Also I believe your 2017 Premium has grill shutters that close when on the freeway to improve aerodynamics. Is the check engine light on? Is your grill free from obstructions?


At the end of the day it's not a complex system and the service guys at your dealer don't need to be rocket scientists to get it dialed in.


In my experience if it's over-serviced, a blowoff valve will eventually release the excess pressure.
 

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Just asking - you do have the selector on recirculate? Maybe the fan speed reduced a notch or two from max? Your outside temps make me think you also do need to tint the windows.
 

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My AC is starting to smell, gotta somehow clean it out? Does the dealer do that? Is it covered since I bought it brand new?
 

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The compressor clutch is just use to shut off the compressor in case of low refrigerant. Most cars today use other technologies to regulate refrigerant flow...expansion valve, cap tube or variable displacement. Using the compressor clutch to turn on and off the compressor to regulate temps was a major source of failure.


You need to go back to the dealer and have them put a set of gauges on the car...that is the only way to evaluate. Also, when measuring proper AC operation, do not use recirculate...put fan on high with fresh air and measure temp in driver side vent. Note, if the dashboard is hot you have to wait for it to normalize. Measure the temp drop and let us know.
 

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Your A/C smells because you run the recirc and it causes condensation to build up in your vents, try running on straight a/c to air it out.
 

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Yeah, I've noticed that the AC in my '17 is terrible in NC (85+ degrees and humid) unless recirc is on. My wife's '14 Accord AC is far better. I asked them to check the pressure last year but they said it was fine. I dunno if they actually checked it or not though.
 

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Can’t autozone check a/c pressure free of charge? Have then check it if you don’t trust your dealership.
My 17 Sport runs cold and thats in a non-humid area like Denver.

Derrick, does the SGP framing on the Ascent look identical(except for size) to the Impreza/ Crosstrek. I saw a Subaru diagram that looked like the Ascent has a slightly beefier structure but other than that is was identical To Impreza
 

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Another consideration (my engineering mind at work)...


Have you considered installing a thermal insulation like dynamat? Not only would this help to insulate the inside of your vehicle, you may be pleased with the hush of silence it also offers.


I had my spare tire removed the other day and noticed that the ENTIRE rear of the vehicle under the flip-up floor is bare/painted steel. I would expect a layer of stick-on insulation mat may help in this area. Also underneath the rear seat is another easy area to access to stick on some insulation matting.
 

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Discussion Starter #15
Sorry ditching the thread for a minute, I’m in the middle of moving and it’s taking a lot of my time.

I did have a thought about the variable compressor bit. There are two types of control mechanisms for variable compressors to modulate the displacement. One is an electronically controlled solenoid, I figure probably controlled by either automatic climate control or a temp sensor on the evaporator. The second is a mechanicallly controlled type, which I think modulates the displacement based on low side pressures. I’m wondering if there’s a difference in how the compressor is controlled with manual climate control vs automatic climate control. Someone above mentioned their Sport model blows pretty cold in the heat of summer, and that trim comes with automatic climate control, right? I just have manual climate control, no internal temp sensor or anything. Is it possible that the compressor isn’t being ramped up to its full displacement capacity?

I have also been monitoring temps all week with the thermometer in the vent to and from work and such. I actually think in my case the sun is making a bigger difference than I thought. Once the sun gets a bit lower, even if it’s still 95-100 degrees, the vent temps drop to 40-50, where I like it. I’m thinking the air from the vents is getting heated by the dashboard when the sun is hitting the dashboard, even after it’s had time to cool off. Perhaps the ducts run close to the top of the dash? As much as I hate the look of those dashboard covers, maybe I should try one...

What about the fact that when I turn on the AC, the low side pipe going into the compressor gets very cold but then warms back up a bit? At first it’s sweating as it should be, but then it warms up enough to where it’s still cool, but not enough to condense water from the air around it. Is that normal when you first flip on the AC? I’m just guessing at this point. Could it possibly be a fault thermal expansion valve? Although if that were the case I would probably have more severe problems...

Maybe I’ll see if I can borrow a set of gauges and take some measurements on a hot day myself. Autozone and OReillys usually have that kind of stuff you can borrow, like code readers, right? Speaking of codes, no there’s no check engine light or anything, someone had mentioned that as well.
 

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Can’t autozone check a/c pressure free of charge? Have then check it if you don’t trust your dealership.
I used to work at AZ. That was not one of the things that they could check. EPA regulations from what we were told.
 

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After the dash cools down and you see a 40 degree temp drop then the AC is working well. Are you measuring with AC fan on high and NOT with recirculating air? You want to measure temp drop from ambient, not the reduced air temp in the cabin. Yes, when using the AC recirculating air will be better on hot humid days...this is just a diagnostic test. 35-40 degree drop (depending on AC performance and humidity) is all you can expect.
 

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Discussion Starter #18
Yeah, all of the temps I was measuring this week was with fan on full blast, dash vents selected, and intaking outside air. Most of the time, I think it’s working as it’s supposed to. But there are times where it’s dark outside, around 80-85 degrees, and vent temps are till only 60 or so. And I’m still slightly suspicious about the low pressure pipe warming up after the AC has been running for a few minutes. Shouldn’t it be cold enough to cause the outside of the pipe to sweat, all the time (at least when the AC is running)?

Like I said, I’m probably gonna have more success by installing some ceramic film tint. I had that in my last car, and it made a drastic difference in the ability of the car to stay cool in direct sunlight.

And I did also notice that after the car has been sitting in the sun for awhile, the initial temps before I start the AC and the engine are upwards of 130-140F. I knew hot cars were really hot, but it does give me a new appreciation for letting the dashboard cool down before I start complaining. It’s just that with a black dashboard and no window tint anywhere, until the sun goes down or I park in some shade (which there isn’t much of), the dashboard never really cools down, which makes my vent temps consistently 60-65 until the sun gets a bit lower, at which point it usually drops to 40-50.

I think most of my problem is that the sun is heating the interior at almost the same rate the AC is cooling the air, which makes for some pretty uncomfortable commutes sometimes. That’s why I think tinting with ceramic or other infrared-rejecting tint is going to help a lot.
 

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The low pressure pipe is the larger diameter one. If it's not sweating that doesn't mean something is wrong. It could just be a result of the evaporator core efficiently transferring as much heat as possible into the refrigerant.



I still don't think we have a variable displacement compressor. There's no additional wiring that would be required for an electronically controlled compressor, and there's no sign of the normally externally visible regulation valve that would signify a mechanically controlled compressor. And there's still the traditional mechanical clutch that disengages when the AC is off.


Ultimately there are a few basic variables that affect the comfort level inside the car. The AC system can remove heat at a rate based on the difference between the inside and outside temps, and the size/capacity of the compressor, condenser, and evaporator. The cabin has thermal inputs based on the outside air temp, solar radiation, and heat from the mechanical systems of the car (exhaust, transmission, etc). And when the car has been parked outside in the sun, that solar radiation gets a big head start by pre-heating the entire car, which is heat the AC system has to dispose of before it can even begin to make the car comfortable.


Did you check for obstructions to the condenser?
 

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After 4 days in Las Cruces, NM with my 2018 Impreza I can report the a/c performance is reasonable in my humble opinion. Granted humidity isn’t super high in NM, but the unit performed well in temps from 90 to 105. The performance is comparable to our 2000 Outback but certainly not as robust as in a typical SUV or larger sedan. I like to start by airing the car out a bit, running the a/c with outside air and then switching pretty quickly to recirculate. It certainly runs better while moving than in stop and go traffic. I find after a few minutes I don’t have to operate the unit at the highest fan setting.

Good luck with your issue keyesrm.
 
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