The temperature sensor is located near the front fan on each of the four chassis. The locations are as follows:
The image to the below shows the air temperature sensor on the SFF chassis. The 2-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 presence of the sensor or the cable is disconnected. Reseat the cable and reboot to see if the message still appears.
If the temperature of the sensor rises above 42° C (107.6° F), the system logs an error (Air Temperature Out of Range) in the Event Log accessible through System Setup. The air entering the customer’s system has exceeded the 42° C standard, and the system must now compensate with increased fan activity and noise.
i have optiplex745sff with intel core to duo processor e4400 2.0gege hz
at the start up error msg appear
1. Alert rare fan failure
press F1 to continue or F2 to run setup utality
plz any one help me to fix this problem
my mailing id is
The Rear Fan is under the hard drive in the sff.
release tabs (2)
hard drive bracket
DELL Hard Drive Blower Fan Plus Hard Drive Bracket and
Fan Caddy for OptiPlex 760 / 740 / 745 / 755 SFF & Dimension 5200c SFF
Dell Part Numbers: NY290, TJ160, NH645, NJ793
Report Unresolved Customer Service Issues here: Dell - Unresolved Customer Service IssuesI do not work for Dell. I too am a user. The forum is primarily user to user, with Dell employees moderating.
I too get this warning:
press F1 to continue or F2 to run setup utility
I moved the HD and turned the computer on, and the fan is running fine. The error seems to intermittent, but I want to figure out what is causing it. What other troubleshooting steps should i take?
i have the same problem with the rear fan
i have dell optiplex 745, i bought it today and it shows the msg
which states rear fan failure
i opened the case and found that there is no rear fan in my computer
i dont think i will be able find the fan here and buy it .
i just want the msg to be removed
Did you ever resolve the rear fan failure? How?
I have not resolved it. Waiting for someone smarter than myself to come to the rescue
The error usually seems to occur when a dual core processor is added to a 745 SFF with no disk fan present. Dell (the bios) seem to think the system will then have disk which needs a fan. The opposite is true as the dual core gives off less heat than a pentium D. A fix which worked for me was to run the sense wire (yellow in my system and at the at the edge of the 5pin connector) to both front case fan connector and also to the matching pin on the fan connector for the disk fan. The rear fan then looks to be present for the bios. You need a spare dell 5 pin connector to do this, Easy to get by buying an old dell 5 pin fan on ebay. You should check the ebay picture to be sure it is 5 pin fan.
This worked for me. I used an old CD Rom cable, trimmed off the lock so it would slip onto the motherboard header, pulled the yellow pin on the front fan connector and reinserted with a resistor lead. Lined up the pin/wire from the header and slipped over the resistor lead.
I did have an issue when all four wires were on the header, the power supply indicated a fault. I trimmed off the three extras and reconnected with just the one.
I now have a great mediacenter box (XBMC) that boots superfast and i dont have to have a keyboard to press F1!
I know this is old post , but I hope that someone will put the pic of the wiring , since picture means thousand words and I am really struggling with this error.
I couldn't find anywhere else better explanation for this problem but still...
I mean, I have no fan on the back of HDD ;front is only one working good but I am not sure what yellow wire is in question.
HDD caddy has fan. not actual HDD
This thread has been locked due to it's age, if you have a similar issue, please use the 'New post' feature at the top of this page and start a new thread. Bev.
If my answer was helpful, please use the 'Did this answer the question' and click: YesForum Member since 2001I am not employed by Dell