Help! QX4 HVAC only blows hot air when set to 85

[OKQX4]

I have a 2001 Infiniti QX4 and my HVAC basically only has 2 settings: cool (values between 65 and 84) and very hot (at 85). Both temps work, but there is obviously a regulation issue.

I assume an adjustment needs to be made or one or more sensors needs to be replaced. Can anyone tell me how to resolve this issue? Thank you.

[yeldogt]

Go to the "how to" thread -- you can download and look at all the service manuals. The ACC has a self diagnostic you can run ........ also the heating A?C manual has other information regarding how to check the system.

[OKQX4]

Go to the "how to" thread -- you can download and look at all the service manuals. The ACC has a self diagnostic you can run ........ also the heating A?C manual has other information regarding how to check the system.

I performed the diagnostic procedure in the FSM and determined that my intake sensor was malfunctioning. It was reading 131 degrees F and should have been reading closer to the ambient temperature (65 degrees at the time). This makes sense. If it is reading 131 degrees even when my HVAC is set to 84 it "thinks" it needs to blow cold air. I assume that if the temp is set to 85 it automatically blows max heat and if the temp is set to 65 it blows max cold regardless of sensor readings. That is why I only got heat on 85.

I ordered a new intake sensor from infinitipartsonline.com for $10.31 plus shipping. It is called a "thermistor" in their parts catalogue. It is basically just a small plug and play wire with a sensor on the end that goes into the black box to the left of where the cabin air filters are located (behind the glove box). I removed a few screws and cracked the box just enough (flexible plastic) to remove the old sensor and insert the new one.

Overall it was a simple, cheap fix and now my HVAC works perfectly.