I measured mine a while back. It was during the summer but I can't remember what the ambient temp was. It stayed between 45 - 48 right at the vent during a 20min drive.

My AC always seems to cycle too much in my novice opinion, but it's been doing that since I bought the truck and it's still working fine 4 years later.

 

Search this topic on the forum.
The electronic controller that cycles the AC compressor is a bit wonky..

There are cheap simple mods to fool it into running colder.

 

Currently it's 76°F outside with 79% Humidity and my left center discharge air temperature is 57°F

 

Rick - will do, the sensor mod is my back up plan vs taking the dash apart.
Rshadd - wish I could get away with 57* down here, 96* with 90% humidity and zero wind today

the first dealer checked codes, temp sensor, vacuumed, weighed and re-filled the refrigerant and confirmed it wasn’t low and is within specs of 48*-52* which I argued its now blowing warmer than when I brought it in. they very rudely suggested if I wasn’t happy with the service to find someone else. A $50 lesson learned on a non-warranty repair, so I’m bringing it to the GMC dealer across the street on Thursday to confirm Service Chevrolet didn’t screw something else up. hopefully they will be of more help. (I use the dealers because of free car rentals). Some other symptoms I’ve noticed, the duck work behind the glove box sweats, water drips out the exit drain and the compressor line barely sweats, this happens only in the morning. Any other time of the day there is no sweating or dripping out the exit drain. Could this be an indicator of something?

 

Some other symptoms I’ve noticed, the duck work behind the glove box sweats, water drips out the exit drain and the compressor line barely sweats, this happens only in the morning. Any other time of the day there is no sweating or dripping out the exit drain. Could this be an indicator of something?

As your truck sits overnight the ambient, humid air infiltrates the cabin. When you start the truck in the morning and the AC comes on, the cold discharge air cools the duct work. In the morning the duct work gets cold enough to cause the humidity in your cab to condense on the cold surface (just like the condensation you get on a cold drink).
The way an air conditioning system works is to transfer heat out of the space it is meant to cool. 48 to 52 degree discharge air is good. The heat exchanger (evaporator coil in the dash) will run about 10 degrees colder than the discharge air (38 to 42 degrees) so if it ran much colder it would be in danger of freezing up. The cold surface of the heat exchanger causes the humidity in the air to condense on its surface and then gravity pulls the water down into the drain pan and out the drain. This is why they are called "Air Conditioning" systems instead of just cooling systems. Humidity removal (especially in the Southeast) is just as important as heat removal in what the HVAC industry calls "Comfort Cooling" systems. If the heat exchanger is below 32 degrees, the water will freeze onto the heat exchanger instead of running out the drain. In order to run much colder our AC systems would need a defrost system like commercial refrigeration systems have.
Airflow across the heat exchanger is going to have a direct impact on the temperature. The slower the air is moving, the more time the heat has to transfer from the air to the heat exchanger. This means you will see a colder discharge air temperature at a lower fan speed. However, if you do not move enough air the overall heat transfer (cooling) of the space is diminished. This is why if you do not change/clean the air filter on your home AC system it will eventually freeze up when the airflow drops too low. Same principle works on the condenser. If you do not have enough airflow across the heat exchanger, not enough heat is transferred from the heat exchanger to the air. The air moving across the heat exchanger will be a higher temperature, but the refrigerant will be transferring heat from the evaporator coil to the condenser coil faster than the condenser coil can dissipate it. The excess heat stays in the refrigerant as it goes back to the evaporator and reduces the amount of heat the evaporator can now absorb from the cabin. For this reason, more airflow across the condenser in hot weather can improve the system cooling performance.

Sorry for the long post, but I have been in the HVAC industry for over 24 years and am currently a technical service advisor and technical instructor for an HVAC mfg....I guess the technical instructor part of me just kicked in.

 

The first problem with these trucks' AC for those of us in the the deep south is that the interior fan is just too small and puny.

Even if the system works well and cools as it should, the fan just can't move enough air.
In my 12 years experience with a crew cab I found that the fan just doesn't have what it takes to handle a cab of that size.

That's one reason I decided to give up my crew as much as I have loved it and go to a standard-cab for my project truck.

 

You say it worked better before and the dealer confirmed it not low. Now if may have to much 134 or more than it had previously taking the system out of its most effective range.

Same place that trucked-up the coolant mix?

 

yep, same place. I've been going to them for over 20 years with no issues. last year they built a new larger facility to handle considerably more Cadillac's and Corvettes, I'm guessing for some reason the Chevy service dept. is now suffering for it. interesting about the overcharging/too much charge, will find out for sure on Thursday.

 

Well, The dealership didn’t reserve me a loner, so I wasn’t able to leave it with them on Thursday. Like the old adage says, “if you want something done right do it yourself”. So I bribed the shop mechanic and borrowed his A/C gauges. Looks like everything is within specs … at low idle (~700rpm) 30 low 215 high, bleeds off to 42 low and 175 high before kicking on again … on two occasions at fast idle (~1,800rpms) the low dropped to 18 then came up to 30 and held until it cycled again, not sure if that means anything … next is checking vent flaps and temp resistor behind glove box ...

 

@Newcolly Adding a pusher efan to the ac condenser would make the system more efficient. You could get all the parts for a hundred or less.

 

Last time I played with this it was about 82* outside here in Florida, and I was getting 48-52* between all of the vents.

 

So if you @Newcoly do a condenser fan , I would wire it so you can easily disconnect it in the months you do not need ac. As I read @10Canyon53 post the fact that the extra cooling from the efan is only needed in the extreme hot and humid weather is correct. But hey if you need it all the time for the motor and transmission your set.

 

In the HVAC industry we do use fan cycling/low ambient controls to reduce the airflow through the condenser coil in cooler weather in applications where there is an internal heat load in the space that requires cooling when most systems are in heating, such as commercial kitchens, computer server rooms, etc. In fact, the company I work for has a variant of a mini-split system for server rooms that can operate in cooling down to an outdoor temperature of -40F. In the case of most applications, and I would include automotive in this, when the outdoor temp drops low enough that too much airflow through the condenser coil is a problem, you are not likely running the AC anyway. So, I do not see any need to disconnect the condenser fan on your truck during cooler weather.

 

@10Canyon53 Okay I was not going to use temp probe for the fan on off switch. Simply use a relay and the compressor cycling,. I'd want the fan on as soon as the compressor starts for ac operation but not for the defrost cycling during the cold part of the year. Any how that's how mine is .Any suggestions like maybe put it on a single throw switch or other?

 

The best way would be to run it through a pressure switch....but that would require a fitting to attach the pressure switch to....

 

Mine runs 45-46 degrees at the coldest setting fan speed of two
2012 GMC Canyon WT 4x4 L4 2.9L