My front AC vents are blowing out hot air instead of cold air when the AC is on. My back air vents are working just fine. Sometimes I think when I turn on the vents in the front it sounds like a hissing sounds from the vents on top of where the dashboard is, but I could be wrong. Sorry I don't know anything about vehicles. Does anyone know what could be wrong?

 

Welcome from Florida. More than likely it is the blend door actuator for the front since the rear is working well.

 

Is the front vent air actually hot, or just "ambient"? Since you admit you don't much about these, take it to an independent ASE repair shop for diagnosis; only such shop can recover and weigh the R134a to determine if slow leak/attrition through the compressor seal could be the issue, especially if it's had zero AC service in the previous 8 or 9 years.

I'm saying a REAL mechanic shop, not a Brake-O that has a "we do AC" sign !!!!

 

I imagine if the rear vents are cooling well, that the system has a good charge of R134a, and that the blend door up front is most likely the issue. The front and rear systems on the Suburban share a common compressor and condenser coil, but each have their own evaporator coil and expansion valve. There is a *slight* chance that there are issues with that, but it is significantly more likely to be a blend door actuator up under the dash. That is the actuator that moves the door that allows hot air from the heater core and cold air passing over the evaporator coils to mix.

There is also a "mode" actuator that controls if air blows out at the floor, the vents in the dash, or the defroster (up at the windshield). If you can change the setting and have the air blowing out the right place, but it is just the wrong temperature, then that points at the blend door actuator.

 

Our 2014 Yukon has at least 4 of these electric vent door/flap actuators inside the dash, and they seem to be not too reliable over time. I cleaned out/fixed one on our 2014, replaced one myself on our 2005, and paid a mechanic to diagnose/replace one on our 1994......

 

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