Dell Optiplex 745 fan loud

so what could i do because since the xps 700 doesnt have a air temp sensor

Hi Wilkoluke,

This appears to be an issue with the Air Temperature Sensor which is not there in Dell XPS 700. Dell Optiplex 745 system includes an air temperature sensor built into the control panel of the system. The sensor measures the temperature of the air pulled into the system and adjusts the system fans accordingly. You are not able to monitor the system temperature using this sensor; it is strictly a behind-the-scenes function.

You may notice an increase or decrease in noise levels from the system depending on the surrounding room air temperature. The temperature sensor is located near the front fan on each of the four chassis. The locations are as follows:

The image below shows the air temperature sensor on the SFF chassis. 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 "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.

If the temperature of the sensor rises above 42 degrees C (107.6 degrees 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 degrees C standard, and the system must now compensate with increased fan activity and noise.

Hope this helps. Please reply if you have any questions.

Hi Wilkoluke,

Please look for the Air Temperature Sensor on the Dell Optiplex 745 system chassis, connect it to I/O board and install it to complete the circuit. This shall help in fixing the issue.

Please reply if you have any questions.

Hi Wilkoluke,

I understand your concern, but unfortunately there is no such option available in BIOS to bypass this feature. This is working as designed.

Please reply if you have any questions.

Hello, this discussion was useful since I bought such computer and I got fixed the air temperature sensor error. Now my Dell 745 SFF runs well but Everest application reports the CPU temp is around 50C and when cpu is running near 100% the temperature gets easily over 60C wich is the max temp described for the Intel Core 2 Duo E6300 wich is inside my pc. Another thing I am wondering : CPU fan does not speed up even a bite when the CPU temp raises from 50 to 62C, why? The fan spins very low whole the time, around 1000rpm. I don't also understand the idea that the air temperature is measured from the intake air. Why it is not measured from the cpu cooler?

hello, that sounds like your CPU fan is broke if its not speeding up as the processor is getting hot.

Fan broke? In that case it would not work at all. Where does the fan controller gets the input to speed up (=raise fan voltage)  if the temperature sensor measures only incoming air? Has anyone tried to change the place of the temperature sensor near the cooling system?

New to the forum. I have about 10 GX620's in my corporate workshop. I have upgraded two 745's to Core 2 Quads (Q6600), so I thought I would stick a 745 motherboard, HP962, in one of the GX620 cases and see if I could get that up to a Quad. It is loading windows 7 very slowly, but I got the ALERT! Air temperature  sensor not found on startup and the fan is running pretty fast. Has anyone ever done this successfully??

Read posts above. Since I have a GX620 I/O with no air temperature sensor on the board, do I need to get a 745 I/O board to solve the alert and fan speed problem??

Sounds like a good idea to take the temp sensor from a 745. I think there is no way to bypass the warning (once I had similar warning but fixed it by re-fitting the sensor plug) Here is the picture where you see what you need http://en.community.dell.com/cfs-file/__key/communityserver-discussions-components-files/3514/8360.temp-sensor.jpg

So I got a temp sensor and I/O board for the 745. Work fine. But if I want to put a Q6600 Core 2 Quad in, I apparently need to have a DQ965GF motherboard. The one I have is an HP962, which might or might not work. I upgraded two prior 745's and maybe I was just lucky they were DQ965GF. How do I tell?? Nothing on the Dell motherboard give any indication, and I haven't found any software (like CPU-ID) that will tell me.  Help. Also I can't tell if its an ATX or a BTX form factor. I think the GF is an ATX. Guess I know just enough to get in trouble. better keep my day job.