It's part of the fan connector.

hi ejn63,

thanks for the reply.

do you mean it is part of the front fan connector (FAN_FRONT) or card cage fan (FAN_CCAG)? or is it on both fans?

The sensor is located on a small printed circuit board at the front of the chassis (the same one that holds your power button, the hard drive light, the diagnostic lights, etc).  The signal goes from that small printed circuit board down to the motherboard via the ribbon cable that connects the two.

The owner's manual will tell you that you must have a second cable plugged into a small connector on that printed circuit board.  While this is true for the older Precision 690, it is not true for the T7400.

If the system is unable to detect the presence of the air sensor, you will receive an error message when you try to boot & you'll have to press a key (F1, I think) to get past the message.  The failure will also be noted in the BIOS system log.

If you're not seeing either of those, you are OK.

Thanks a million CueBoy for answering my question!!