Hi ch47keeper,

The temperature sensor is located near the front fan on the chassis. In the Optiplex mini tower the temp sensor is integrated in the from I/O panel.

The image below shows the air temperature sensor on the mini tower.

 The two-wire cable runs across the bottom of the chassis and connects to the I/O panel.

If the cable from the control panel to the system board is disconnected, the system displays an error on boot:

Alert! Air temperature sensor not detected

This message indicates the system did not detect the sensor or the cable is disconnected. Reseat the cable and reboot to see if the message still appears.

Please reply for any further help.

The i/o port I have does not have any open slots or prongs on it at all. The part number on the sticker is cn-0mj047-13740-69h-04gi. Is this the wrong i/o port for a 745? Thanks....

Hi ch47keeper,

Please private message me the service tag of the computer, I will check the right part number for the I/O panel and air temperature sensor and guide you further.

To private message, accept my friend request; click on my user name and click start conversation. 

Awaiting your response.

I too have a 745 and have discovered the front panel air temperature sensor. I run Linux and 'sensors' on this PC but no sensors are detected. Could you let me know what the sensor is for the air temp and the bus is it connected to?

The image does not show a mini tower it shows a SFF case.

On mini tower the sensor is a transistor on the USB/Audio board CG250.

The place that failed could be on the panel OR on the ribbon cable.

745 Front I/O USB Audio Control Panel Board TJ853 CG250

Dell Optiplex 740 745 Front Panel USB/Audio Cable - WC679

Models: DCTR, DCNE, DCSM, and DCCY
Regulatory Model (Mini-Tower): DCSM
Regulatory Model (Desktop): DCNE
Regulatory Model (Small Form Factor): DCCY
Regulatory Model (Ultra Small Form Factor): DCTR

2 is the air sensor cable.

MJ047 is a GX620 Front panel board and does not have a sensor.