Wish A/C were cooler, 4.6L

[MarsellusWallace]

I know this has been discussed before, but it's been very hot here in NorCal and I am constantly wishing the A/C were better. It's not broken, blows somewhat cold, but just takes forever to cool down the cabin.

My 2010 4.6L has 120k miles and I just replaced the alternator and battery. Is it worthwhile to take a look a changing out the A/C compressor? Anybody got a big improvement?

 

[mikec]

Many folks have noted the Genesis A/C doesn't seem to blow as cold as other cars and that it won't do much of anything until the vehicle speed reaches 30 mph or so...

My 2009 V8 was that way. Recently it was obvious a leak had developed as the A/C outlet temps were nowhere near "cold" even after a few minutes of driving. An A/C manifold gauge set confirmed some refrigerant loss. I found greasy/dirty fittings at one junction and re-did that connection (I have the equipment to do basic A/C work) and then re-charged the system myself. I re-filled until the manifold gauge pressures corresponded to "typical" values of R134a systems at the ambient air temps that day. When done, the center vents were blowing 40 to 42 degree air. On a 90+ degree SoCal day. Better than ever!

Why are you thinking "A/C compressor" right off? That's likely not it; they tend to either work or not work at all... rarely "half working." And compressors will often make noise when bad. Low refrigerant pressures, from leaks or damaged hoses, are much more common. Until a proper manifold gauge set is connected to your car and the readings analyzed, most diagnosis will be guesswork - unless there are obvious physical signs like noises, vibrations, or a greasy mess around joints/fittings. In my case, it was the expansion valve area - you'll see an aluminum rectangular block centered along the upper back edge of the firewall with the A/C piping going to and from it. Bad electric fan motors at the front of the car cripple the system by reducing heat transfer.

A/C systems work by "moving heat" from one area to another; in cars that means from the evaporator assembly (the part under the dash that cools the air by extracting heat energy from it) and dumping that heat energy through the condenser (A/C radiator at front of car). The compressor raises the refrigerant pressures - and thus the temperature (ideal gas law) which is (hopefully) well above outside air temps. That hot refrigerant flows through the front radiator where the heat is transferred to the outside air. The cooler (not cold yet) refrigerant then flows to the expansion valve, sometimes an orifice tube in some types of cars, which you can imagine as a washer inside the A/C pipe. What was a pipe suddenly ends in a pin-hole sized passage. So only a little refrigerant at a time fits through it... and ends up in a larger diameter pipe so the pressure now drops suddenly. That sudden pressure drop also causes a big temperature drop... the refrigerant now is "ice cold." It's passed through the condenser to extract heat from the air flowing past it, cooling that air which is then blasted into the car interior. To increase the "heat moving capability" of an A/C system there are a few options:
1: Change to a refrigerant with a different "n" in the ideal gas law: Pressure * Volume = n * R * Temperature. R is one of those physical constants. This typically requires a different expansion valve/orifice tube though, and adjusting the diameter of the A/C piping, to match.
2: Larger condenser and evaporator assemblies to aid heat transfer. Or better fans to move more air across those surfaces to improve heat transfer.
Higher system pressures really won't make as much of a difference; the pressure needs to be matched to the refrigerant type and condenser capability. R134a has less capability than the older R-12 (Freon) so cars designed with R134a air conditioners typically have larger condensers to compensate. Excessive pressures typically cause other issues too. While the compressor outlet pressure and temperatures can be raised this way, the expansion valve won't be able to drop the pressure as much (because the piping just downstream of the valve will be at a higher than normal pressure due to the excessive refrigerant quantity) so the net pressure change across the valve won't be much larger than a properly filled system.

edit: Other issues folks have run across:
1: the little motor driven diverter valves under the dash (they route air across the A/C evaporator or the heater core) don't work right so some heated air ends up being pushed into the cabin. Typically one vent, or driver vs. passenger side of the car, will have wildly different outlet temperatures.
2: on the back of the center console are vents for rear seat passengers. These include an airflow volume control and a temperature control. Is that temp control set to HEAT instead of cool air? Sometimes the control "drifts" towards heat as the car is driven. One forum member used a bit of paper or cardboard (a matchbook cover I think it was?) to hold the control in one position.
Either issue ends up putting heated air into the car, fighting the A/C conditioned air.

mike c.

 

[EdP]

I know this has been discussed before, but it's been very hot here in NorCal and I am constantly wishing the A/C were better. It's not broken, blows somewhat cold, but just takes forever to cool down the cabin.

My 2010 4.6L has 120k miles and I just replaced the alternator and battery. Is it worthwhile to take a look a changing out the A/C compressor? Anybody got a big improvement?

Don't be so quick to change out a compressor. Two things you can do. One is to actually measure the temperature coming out the vents when running to see how much temperature drop you are getting. it will vary but should be less than 45 degrees if it is 80 outside. You don't want less than 35 or you can freeze the evap coil. At any temperature you should see a 35 to 49 degree drop.

For a few bucks, an auto AC shop will put gauges on the system. That will tell if you have a full charge. It is not uncommon to have some loss over the years. That will tell you if the system is operating properly. Of course, your expectations may differ from what is possible. You won't get it down to 65 degrees inside, but then some people would put a sweater on at 80.

Oh, make sure someone did not turn the rear seat vents to warm if you have such a thing and check the cabin filter.

 

[Bill K]

Getting your car AC system checked can cost from $35 to over $100.

 

[PMCErnie]

After you get the AC working properly, also consider a quality and legal tint job. My interior is heavenly after installing Llumar air blue 80 tint.

 

[OUsig]

my AC is pretty weak especially if you are sitting/idle. Drive at speed and it will get cold as needed but slow driving or stop and go and it really is not cold. Almost seems like the engine fan isnt blowing fast enough to compensate at low speed but I have checked in my garage and it is blowing full speed with the AC turned on.
Unlike our other vehicles in the same driving scenario - heck even my work vehicle AC beats the heck out of the Genesis. I have spent a good bit of money on this car in the last year. Guess an AC check is next.