2011 Cayenne S. I have searched the forums and have found some related posts but not exactly what I'm facing (it seems). The problem is there is only cold air coming out of the drivers side vents. Air flow is normal and can be switched from dash to floor to defrost just fine. On the passenger side, the air is blasting hot, I assume trying to warm the entire car. The passenger side heat will start to calm down after the cabin is warmed up but I usually have to the passenger side heat down to like 65 to not roast a passenger until it gets there. The temperature of the air on the drivers side vents are always cold no matter the position (floor, panel or defrost).

I have run diagnostics on the HVAC and there aren't any codes. I have run actuation tests on all of the 8 or so different servo's in the system and the actuation tests comes back that they are all operating normally. I have looked at discharge temperatures from the various sensors and notice one peculiar thing. The sensor in the floor vent area (drivers side) is registering around 120 degrees even when I just start the car. i can look at the temp readings of the other sensors and you can see all of them start out on a slow climb as the car warms up and thus the heater air starts to warm up.

Even in my workshop manuals, i cannot find any description of how the control module works in combination with the various sensors and servos. One possibility that I thought of is that the control module is seeing the drivers side temp from the floor sensor putting out really hot air and adjusts all of the heat to the passenger side (this would be despite the temp sensor at the dash level, driver side showing a normal temp). So before I just buy a temp sensor to see if that would fix anything, does anyone know how the hvac control module logic works with the various sensors and servo's that might help me to identify fault that doesn't throw a code?

Thanks

 

Is it easy to switch the passenger side and the driver's side to see if the issue flips also?

Im going out on a limb and thinking that even if one sensor is bad, then that side will register bad.

 

I was going to do that actually but when I removed both sensors, the one under the drivers side comes out as an elbow shape while the one on the passenger side is a straight plug. I tried a little bit to get the passenger side into the drivers but couldn't get it to fit in (I'm working blind at that point as I didn't take off the plastic air diffusor and it plugs into the top of the diffusor). For whatever reason, the temp sensor on the passenger side doesn't plug into the diffusor. It fits into a bracket sitting directly behind the diffuser. Maybe worth trying again or I'll just buy a $40 temp sensor and see if it changes anything if I can't find anyone with insight into how the control module works.

 

the sensor does not show a code when it reads incorrectly only when shorted. I had this issue. Change the sensor and your problem will be solved bye to verify it’s the sensor raise the temp till it says hi. That bypasses the sensor. I hope there’s a high I know there is a low

 

Thanks. i will see if I can raise to high (I don't know if there is one either as I don't drive this car usually).

 

Raising the temp setting to high does in fact divert hot air to the drivers side. I will proceed with changing the temp sensor in the footwell and see what happens.

 

Did that fix the problem?