Fans on all the time on Z820

[Rich999999]

Hi, I've got an old Z820 workstation, and sometimes the system fans stay on full blast for no apparent reason - there's no workload, the system temperatures are all low, yet the fans are on full blast. Other times, they only come on under load. Any ideas why this might be, and whether anything could be done about it?

Thanks!

[DGroves]

when the fans go full speed check the ambient air temp using the HP advisor program

your ambient air temp sensor (located in the power cable) or the circuit on the board may be failing

search this forum for numerous previous posts on this for more information

[Rich999999]

Thanks, I wasn't aware of that app to read the temp sensors (for some reason other temp sensor programs don't pick the sensors up). You're right, it's reading 127C for ambient temp, will look into replacing the power switch cable/sensor.

[DGroves]

you can also try replacing the sensor in the cable, it's near the button end covered in black heatshrink, and it's a common npn transistor you can use a 2n3904 or a 2n222a plastic body transistor as a replacement

note that the existing transistor will have two leads connected together and a single lead connected to colored wires,  match the existing leads  to the replacement and also note which lead connects to which color wire

you might also be able to use the z620 power cable on the z820, i know the z600 cable length will fit the z800 just barely

[Rich999999]

Thanks, but I'm not really up to soldering! I've been looking to get a new part, but I can't find it on HP.com, and I don't really want a refurbished part, in case it's duff as well. As far as I can work out, the part number is 644320-001 and/or 644320-002? But I can't find it on HP.com?

[DGroves]

if hp still has stock it will be over 100.00 for the part

buying it from major companies who are HP authorized will be much cheaper

https://www.alancomputech.com/hp-z820-power-button-with-speaker-new-644320-005--644320-005.html

there is nothing wrong with buying used parts from people parting out systems on ebay as ebay will stand behind any sale where the seller says a part is in working order and refund the purchase price if the sold part is non working

[Rich999999]

That's all good to know, thanks, and thanks for the correct part number. Unfortunately I can't find anywhere in the UK that has it, and shipping from the states in >£100!! Time to go find a friend who's handy with a soldering iron.....

[DGroves]

as i pointed out, a z620 power cable will also work and they are far more common

https://www.ebay.co.uk/itm/HP-640982-001-Z620-Workstation-LED-Power-Button-Cable-Assembly-Tested/153...