Question "Rear chassis fan not detected" error on HP Compaq 8000 Elite ?

Apr 22, 2021
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So I purchased my Compaq 8000 Elite secondhand from a liquidated company that used to run their computers hard for years in early 2020 as the primary computer for an arcade cabinet I am building. However, I noticed the rear chassis fan was starting to get loud and sounded like the bearings were starting to go. So, I pulled the fan, and installed one of my spare 92mm Noctua brand fans to keep it cool and quiet. After doing this, however, the computer started booting to a "512 rear chassis fan not detected" error.

Naturally, since I've already learned this unit does not like anything not HP branded when I tried to replace the RAM (gave a motherboard failure beep code when new RAM was installed), I went ahead and installed the old fan again. Now, it consistently boots to that error message. What is weird is that the fan is very much on, and the computer ramps it up to full speed over a period of 45 seconds after the POST error.

Here's what I have done so far:
  • Disassembled and reassembled unit
  • Cleaned contacts
  • Updated BIOS
  • reinstalled drivers (drivers were missing in my Windows install)
It is currently at my work getting looked at, but they keep turning it off because of how loud the fan is at full run. What can I do to resolve this? There's nothing in the BIOS that allows me to turn off a presence check on the fan.
 

hang-the-9

Titan
Moderator
Mar 25, 2010
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Sounds like the fan header is not seeing the fan, either it's broken or not plugged in properly. Fan will work just fine with the power going to it, but for the motherboard to "see" it, it needs the properly fan header connection working. If nothing you did fixed it, and it's not seeing it on the original fan either, it's likely a broken header. Maybe the other fan you connected causes a short there.
 
Apr 22, 2021
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Sounds like the fan header is not seeing the fan, either it's broken or not plugged in properly. Fan will work just fine with the power going to it, but for the motherboard to "see" it, it needs the properly fan header connection working. If nothing you did fixed it, and it's not seeing it on the original fan either, it's likely a broken header. Maybe the other fan you connected causes a short there.
Could be, I popped in another new Noctua fan, as the old Foxconn one now sounds even worse, and same issue is still present. Do you think that the header itself is damaged? And would that be fixable if so? It’s a standard 4 pin fan header, that’s why thinking it may have shorted is weird. I can send pictures of what everything looks like once I’m in front of it again.
 

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