AC/heat issues

[Gameoverlord6t9]

I have a 2018 Tahoe LT, 5.3 flex fuel.
A few years ago I was changing the cabin air filter, I had to move a wiring harness that was hanging in the way that was to the right slightly, after that the AC/heat started acting up, it would seem to shut off the AC with the fan still blowing, and the heat was non existent unless it was turned to max. I took it in and had the blend door actuators changed, still same thing, I then took it in again, all under warranty, and they stated the EVAP core was leaking, so all the blend doors, actuators and EVAP core were changed out. Now the air was so cold it was freezing, even if set at 80° with AC on, didn't matter if the dual climate was used or not, but the back seat functions just fine. It would get so cold the air flow would shut off even when the fans are full blast, shut off AC and slowly the air pressure would come back, even shooting out ice chunks a few times. I had them check everything and was told nothing is wrong, usually does it after 30 minutes of driving or so, so their technicians can't replicate, but still not heat, even with AC off, defrost fogs up the windshield even and the vents do the same thing but faster. Anyone else deal with this ridiculous issue.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

This is truly and odd one, and I cannot personally assist you with your issue. But other members of this Forum much more knowledgeable than me in this area will chime in. @swathdiver

 

[Gameoverlord6t9]

 

[swathdiver]

@91RS @rockola1971

 

[rockola1971]

You have a blend door problem or its motor. Its possible the blend door pivots are broken and the door is jammed into place. You arent gonna like this but this is NOT a fun job. Have a look at youtube vids for shortcuts to check and do the R&R. If its just the motor then it wont be so bad. A scan tool will confirm your motor.

 

[Gameoverlord6t9]

You have a blend door problem or its motor. Its possible the blend door pivots are broken and the door is jammed into place. You arent gonna like this but this is NOT a fun job. Have a look at youtube vids for shortcuts to check and do the R&R. If its just the motor then it wont be so bad. A scan tool will confirm your motor.

Two dealerships have replaced blend doors and actuators. EVAP core was allegedly leaking and changed out. Asked them to check compressor and both the high and low pressure sensors. Said it was all good. Just gets super cold no matter the temp setting or dual settings. Rear function normally. No heat or front defrost. Vents will lose pressure, like the vents are slowly closing, fan still blowing, turn off AC button and it slowly blows again, with ice chunks flying out. I thought it might be an ambient air sensor. But moving the harness by the cabin air filter housing started all this. All work was done under warranty. But still doing the same thing. I'd hate to think that both dealerships misses a loose wire or relay. I was hoping someone else had same issue and knew the answer

 

[rockola1971]

Two dealerships have replaced blend doors and actuators. EVAP core was allegedly leaking and changed out. Asked them to check compressor and both the high and low pressure sensors. Said it was all good. Just gets super cold no matter the temp setting or dual settings. Rear function normally. No heat or front defrost. Vents will lose pressure, like the vents are slowly closing, fan still blowing, turn off AC button and it slowly blows again, with ice chunks flying out. I thought it might be an ambient air sensor. But moving the harness by the cabin air filter housing started all this. All work was done under warranty. But still doing the same thing. I'd hate to think that both dealerships misses a loose wire or relay. I was hoping someone else had same issue and knew the answer

If you are blowing ice chunks out of the vents then your evaporator is freezing up. There are 2 general causes to this. Low refrigerant charge or lack of airflow across the evaporator. The air flow problem could be a fan speed issue, plugged up cabin filter, dirty evaporator(plugged up), blend door incorrect positioning. When R134a is at 27.8 PSI or lower the evaporator will be 32deg or lower which means all humidity in the air going through the evaporator will freeze solid. This is why an evaporator freezes up on a low charge (leak) system. A system pressure check needs to be checked when system is freezing up to see that low pressure value. If its not lower than 27.8 PSI then you have an airflow problem. There is a sensor in your airbox left of fan that controls your fan speed that is used in the auto climate control GM system. Id remove it and ohm out its different resistive values to check all paths are good. If they are then your head unit or associated wire problem would be the culprit.

 

[Gameoverlord6t9]

If you are blowing ice chunks out of the vents then your evaporator is freezing up. There are 2 general causes to this. Low refrigerant charge or lack of airflow across the evaporator. The air flow problem could be a fan speed issue, plugged up cabin filter, dirty evaporator(plugged up), blend door incorrect positioning. When R134a is at 27.8 PSI or lower the evaporator will be 32deg or lower which means all humidity in the air going through the evaporator will freeze solid. This is why an evaporator freezes up on a low charge (leak) system. A system pressure check needs to be checked when system is freezing up to see that low pressure value. If its not lower than 27.8 PSI then you have an airflow problem. There is a sensor in your airbox left of fan that controls your fan speed that is used in the auto climate control GM system. Id remove it and ohm out its different resistive values to check all paths are good. If they are then your head unit or associated wire problem would be the culprit.

The dealerships told me everything was ok when it came to pressure sensors and freon levels, they prolly lied. It acts like there is no heat no matter what, even when AC is off, heat set to 80 feels like 60 without AC on. No change til around 84 and it still tapers off cool. It's an 18 so it has dual climate, that makes no difference either with temps being set different from each other, but the rear operates normally still. But I'm still gonna check the freon levels, ohm out the pressure sensors. The fan never shuts off, can still hear it blowing, just the EVAP core freezes and cut off airflow. Gonna double check what you said though.

 

[Gameoverlord6t9]

If you are blowing ice chunks out of the vents then your evaporator is freezing up. There are 2 general causes to this. Low refrigerant charge or lack of airflow across the evaporator. The air flow problem could be a fan speed issue, plugged up cabin filter, dirty evaporator(plugged up), blend door incorrect positioning. When R134a is at 27.8 PSI or lower the evaporator will be 32deg or lower which means all humidity in the air going through the evaporator will freeze solid. This is why an evaporator freezes up on a low charge (leak) system. A system pressure check needs to be checked when system is freezing up to see that low pressure value. If its not lower than 27.8 PSI then you have an airflow problem. There is a sensor in your airbox left of fan that controls your fan speed that is used in the auto climate control GM system. Id remove it and ohm out its different resistive values to check all paths are good. If they are then your head unit or associated wire problem would be the culprit.

Oh and the freon is the R-1234yf pag oil freon.