z620 rear fans spin too fast and make too much noise

[scasparz]

Hi,

All of a sudden my trusted z620 has accelerated the spinning of both rear fans, just under the PSU.

Made a google search, found a number of reports on fan spinning, nothing on par with my case.

This is what I know so far:

1. No recent changes have been applied to either hardware, firmware, setup (F10) or software.

2. Computer has been cleaned recently, no dust traps are known to exist, nothing blocks internal ventilation anyhow.

3. Am getting no warning messages or beeps. Have inspected SYSLOG for anything unusual, none was found. Instead, other than the rear fans, everything seems to work flawlessly. Have inspected every known fan one-by-one, all were found spinning normaly.

4. Have grounded myself and touched every internal surface by hand, none of them appeared to be hot, CPU included. Looks high fan spinning is totally unjustified, at least temperature-wise.

5. Have disconnected every HDD, system won’t boot, yet problem persists. This is not a software issue.

6. Have removed every internal peripheral including the second processor riser card and even the VGA card. Problem persists. Am left to believe this is by virtue of a faulty temperature sensor.

How can I locate and replace this sensor, or should alternatively contact some authorized HP service instead?

regards

s

[DGroves]

your ambient temp sensor which is located in the power button harness may have failed either replace the sensor which is a common transistor model, (search this site for previous posts on ambient temperature sensor) or buy a replacement power button harness

symptoms of failure are when powering on case fans start normally then ramp up to full speed due to the failed sensor number

you can also install the HP hardware diags which i believe will also show the temp sensor reading value

https://www8.hp.com/us/en/campaigns/hpsupportassistant/pc-diags.html

[scasparz · Accepted solution]

Many thanks mate for pointing me to the right direction. Symptoms on my z620 are exactly as you describe. 

kind regards

s