Hopped in my 2016 Z tonight for a quick drive. Ambient temps around 72-73 degrees. I had both passenger and driver temp controls set to 69. As the car started to warm up, the passenger side was blowing cold air from the AC, but the driver’s side was blowing HOT air. I turned the **** all the way to LO and it cooled down to “Luke warm”, but not what I would expect. Eventually, it started blowing cold air and I was able to set it back to 69 and the air temp from both sides was the same.

Anybody ever experienced this before?

 

I had this happen once in my 2017 - I had to play with the temperature control, turning it all the way up and all the way down again in order to get the cold air blowing on both sides. Has not done it since.

 

I've had it happen occasionally, cranking the temp control to minimum and back to the desired temp fixes the problem.

 

This did not happen to my Corvette, but the identical thing happened to my Yukon Denali two days ago.

As the ambient temperature was reaching 100 degrees a few days ago, the interior of the Denali was not cooling well. I thought the AC was failing. So I checked the passenger compartment and found the vents were blowing hot air. The temperature settings for both were set to 60. I was never able to get the passenger vents to blow cold.

I shut the AC system completely down, OFF and then back ON again. This somehow reset the vents and the AC system began to control properly. Perhaps this is a common problem with all GM AC systems.

 

First check the fuse box. Even though highly unlikely, it is the easiest thing to do. I believe there are a couple of fuses for the HVAC controls in the main fuse box. Fuse #3 and 28.

I do not and have not had this issue in my Corvette (knock on wood), but had this same issue on our old faithful minivan. So I can tell you what I learned when I diagnosed and fixed the issue (or issues) on it.
When you have two different temps coming form the AC outlets, while you have set the temp to the same value on both sides, it can be one of three issues.
1) One of the thermistors (temp sensors) have gone bad and is not giving the right temp feed back to the HVAC control module. This is not common.
2) One of the damper motors have gone bad. This is more common then #1 above but usually happens to vehicles 10+ years old and 150k or more miles. So this may not apply to you or any C7 Corvettes since not many are driven 15-20K miles per year. I had to dismantle and clean the driver side damper motor on the van. Have been working fine for the last two years now.
3) Low refrigerant in the system. This is the most common culprit. When the refrigerant is starting to go low, one side of the evaporator gets fully cooled while the other side only get partially cooled (or not cooled at all), and since the air is just pulled from one side to go to the left and the other side to go to the right, one side of the vehicle will not cool as much as the other. This starts gradually and the dampers are able to compensate for this initially, but they can do only so much and one day you get worm or hot air from one side. If the fuses are good, then get the refrigerant checked. This happened on the van about a year after I fixed the motor (at age 14, van is almost 15 years now, keeping it another year so I can teach my son driving). Found the correct refrigerant type and bought a refill can from Wally world. Been blowing cold air since. The very slow depletion of refrigerant is due to an extremely slow leak in the system and mechanics will most likely never be able to find the leak, unless the lines had a fatigue related puncture. So the solution is to re-fill and move on as opposed to replacing parts or the entire cooling system. If I remember correctly, mine was down by just a few psi in the low pressure side.

Hope this helps.
Good luck and best regards,
Vip.

 

Some comments on this one, if it blows full heat on the driver's side while the passenger side is the correct temp, OR if it seems to come and go (both sides blow cold but then driver's side heat), it is not low refrigerant.

There was a tech bulletin on this as well, that first recommended reflashing the HVAC controler with the latest software version. This may also be an "easy" thing to try.

If it goes full heat, most of what I have seen is it is the blend door actuator gone bad. This is a large job on the C7 as the entire dash gets disassembled to get at the actuator.

 

@LiManZ06 Did you find what was wrong with the AC?

 

I have not had time to address it and honestly unless it reoccurs, taking it to the dealer will result in a diagnostic charge and “could not reproduce”. Been down that road before.

If it happens again I’ll address it. I’ve only driven the car once or twice since my original post.

 

If you have a OBDII scanner, check for codes. Mine did this and when I went in to the dealer they found codes and eventually ended up replacing my A/C head unit. it's been working better since then.

/JD