So, on the way back from Disney right now. My 2015 silverado started blowing cold-ish air no matter what temp it was set to.
I bought a can of refrigerant with the pressure gauge on it (I'm not home yet to hook up proper gauges). The pressure gauge on the can said it was on the high side of the green zone.
Compressor is spinning. Air is definitely colder than the 95 degree outside temp. But probably like 80 degrees inside temp.
Any first thoughts before I get the gauges connected to it?
When you turn the temp to s low as it gets, the blower motor speeds up, so I don't think its a "switch" issue.
Doesn't matter if it's on recirc or not.
Doesn't matter what vent setting (yes, the button for changing vent settings works and the vents change as they should).
I can't understand how the compressor is turning, it has enough charge, the blower is functioning, and it's blowing kinda cool air. Not warm. Not hot. Not cold. Kinda cool.
Annndddd..... Go!
Really need to know what the high side pressures are at, with a gauge or scan tool data. Also, it would be good to know what the actual discharge temperature is. Auto parts stores sell little thermometers on a stick that are perfect for this, usually $5-7 and stocked near the A/C paraphernalia.
Does the vent output get hot if you turn the temperature up, and can you hear the blend door moving/hitting its stops when you move it from cold to hot, then hot to cold? (It may take a few seconds to register the change and then move)
Does the radiator fan work properly? The last "poor A/C" diag I did turned out to be a fan that had unplugged itself. No mention of overheating, just that the A/C didn't work 
(There was a code in the PCM for overheat and the failure record showed that the cylinder head temp was 267F when it set) I am fairly sure that your vehicle has electric fans with a twin fan setup and three relays to give "low speed" (fans powered in series) and "high speed" (fans powered in parallel). I *think* that high speed is only controlled by coolant temp, not A/C pressure. If there is any kind of fan issue then air conditioning is going to suffer, even if the engine seems to be running at the right temperature.
Another goodie, I had one car with automatic climate control that had poor output because the driver was holding a cold beverage on his knee, very close to the cabin air temperature sensor. If it sees that the cabin is already cold, it will adjust for that. Same effect as having a portable heater in your living room close to the house's thermostat.
One more. I had a plow truck with an HVAC concern that was traced to someone having routed the plow control pendant wiring THROUGH the control linkage on the left side of the HVAC case, on a similar year Silverado. It was keeping the door from moving.
Another fun test that works especially well if you don't have dual zone climate control: If it's warm on the passenger side and cold on the drivers side (or vice versa depending on the evaporator geometry) then it is most likely just low on refrigerant. It all evaporates in the first half of the evaporator and not all the way across.
This works on dual zone systems too, but you need to make sure in that case that you don't have a blend door hanging up. This is where you need a scan tool that can read HVAC data. And hope that the manufacturer is kind enough to give you blend door position in that data. (Not everyone does. GM and Ford do, at least)
Let me cover some of this.....
Sounds like the flappers are moving correctly. If you turn the temp up above 80 degrees it gets hot. No cold beverage near the thermostat.
This has dual auto climate control. Vents both sides are the same.
No plow. No changes from 3 days ago when it worked perfectly.
Fans are both turning. Went to high speed when sitting in a hot parking garage in Orlando. It's way obvious when both fans go to high speed. Temp indicated a little high. Both fans on high temp brought temp back in 10 seconds. Ac was still cold then. (2 days ago)
Edit to add.. haven't gotten the gauges on yet. It can sit for a day and think about what it did. I just unpacked from Disney. I'm watching highlights from indycar right now.
The fans went to high just when sitting still? Hmm.
Do they work on low speed?
Okay, it's currently 80 degrees. Here are the pressures...
36 low side and 205 high side.
Fans are both running at "normal" speed. Air inside the truck is cool. Not cold.
It would freeze you out previously.
After about 10 minutes, here is the pressures...
Does your low and high side not running approximate ambient?
Ranger50 said:
Does your low and high side not running approximate ambient?
Low and high are equal at 90 psi at 80f ambient.
Can I ask does it have a cabin air filter?
In reply to Ranger50 :
It does. It's probably dirty. But the fan still blows full force.
I am going to check the blend door tonight. I watched a video and it's apparently easy to see if the blend door actuator is actually moving or not.
In reply to wvumtnbkr :
But if you don't have the same available airmass, the fan blowing on high doesn't mean crap. I mean if I put a smaller flowing carb on my engine, I don't expect it to make the same hp as before no matter how hard I turn it. Similar thing here.
Change the filter, just because. I just had the same issue on our car, and changing the filter did the trick.
Annnddddd... it seems to have fixed itself. I hate intermittent E36 M3.
I'll still check / change the filter.
I'm assuming 134a system? At 80F your low side should be between 40-50, your high side looks like it is in the right range. I'd add part of another can and see what it does.
Then try to figure out if the leak is slow and it finally affected performance or fast and it quits working again in a few days.
The pressures looked good, but like the A/C wasn't working very hard, which smells to me like a control issue, like the control head didn't see a reason for you to need much A/C so it wasn't allowing the blend doors to go full cold.
The fact that it started working normally again seems to reinforce this.
Pete. (l33t FS) said:
The pressures looked good, but like the A/C wasn't working very hard, which smells to me like a control issue, like the control head didn't see a reason for you to need much A/C so it wasn't allowing the blend doors to go full cold.
The fact that it started working normally again seems to reinforce this.
That's how I'm feeling currently as well.
If it does it again, I'll see if I can see the blend door while its happening.
I ordered a new blend door actuator (like 25$ from rockauto).
I wonder if GM uses a sunload sensor.
You can create problems by throwing maps or other paper stuff on the dashboard, covering the sunload sensor, on some vehicles. And Nissans are so "dumb" that they will set a code for it if you scan the HVAC module while the vehicle is indoors...
(Edit: Apparently there is one, but I can't find a diagram of where it is without being at work. It's either a flat panel in the left dash speaker or a dome looking thing in the middle front of the dash pad)
If it happens again, and if you have a scan tool that can read HVAC, and IF they are kind enough to tell you commanded position as well as actual position, that will tell you if it is a mechanical problem or if it is being commanded to do what it's doing.
OMG.... I had the paper on the dash from the resort we were staying at. I NEVER leave stuff on the dash.
I'm gonna grab something and see if I can recreate it.
Edit... I will do this test, but I would think if you set it to full cold (we did) that the paper on the dash wouldn't matter.
