HVAC - '08 Impala

chuckingresham

Here is my issue. Our Impala, when AC is on, blows cold air on the passenger side and blows hot air on the drivers side. With the key on, engine off, I can turn each side from heat to cool and can hear the blend door changing positions on both sides with no clicking. Doesn't seem to me the blend door actuator motors are the problem. What else could be going bad?

imidazol97

Low freon could be the problem but diagnose a little more.

If you have dual temperature controls like it sounds, check that you can change the temperature on each side from cold (or not very cold on the driver side) to hot air and back. That would indicate both blend doors have movement and the actuators are working.

If you are savvy on safety in the engine compartment, with the engine running and the AC on with the blower on a medium to high speed, feel the temperature of both metal tubes for the freon where they go into the firewall. The tubes should both be cold. In fact, the outlet should be colder than the inlet with the perfect fresh charge of freon.

If you want to assess the state-of-charge further, lower the blower speed to the lowest speed and put the AC on recirculate and let it stabilize for a few minutes with the door closed. Then feel both tubes again. If the one that was not very cold is now a little cooler, that verifies that the system is low on freon charge.

Some of the systems have the air from the driver side going through the evaporator portion where the freon goes last. The freon liquid already gave up its "cold" by being evaporated to gas on the passenger side, so there's little cooling done on the driver side of the evaporator.

Another empirical test is if on a cool morning below 70 you start the car and turn the AC to cold on both sides, you feel like the driver side is cooling okay again, that's because the air going through doesn't evporate all the freon on the passenger side before getting to the driver side, so there's still some freon to take the heat out of the driver's air.

My suggestion is to have a reputable, knowledgeable shop take the freon out, vacuum the system to check for leaks, and refill with exactly the engineering design amount of freon. I do not recommend do it youself cans which can contain additives and because getting the right amount in is tricky with the variable compressor. Pay once to get it done right. Likely that it's not got a leak but just has a slow seep that over 11 years has lost some freon.