# Fan Error on boot



## prsings (Oct 31, 2005)

This is more of an annoyance than a problem. When I boot, or reboot, I get a two-beep error on the initial black screen. "Alert, previous fan failure" I know what happened, when I replaced my case fan, I didn't have a full connection, saw it right away and reconnected with no problems.
Is there a way to stop this message from appearing? I have gone to my bios and selected "mark all messages read." Any help will be appreciated.


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## redsunx (Apr 5, 2007)

um do all your fans have a yellow wire on them if not thats it ,should be just trying to autodetect it


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## prsings (Oct 31, 2005)

The case fan has a yellow wire on it. It works fine, I put in a quieter one and started the computer with it disconnected.

The actual error message is "Alert! Previous fan failure. Press F1 to continue. Press F2 to enter set up. The key word is previous. F1 always works fine.

I thought, at first, that the fan wasn't running, it is so quiet, but I put my hand behind it, and felt it blowing.


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## redsunx (Apr 5, 2007)

do you notice any real problems?


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## Terrister (Apr 18, 2005)

What is the make and model of the computer?


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## prsings (Oct 31, 2005)

My Computer:
Dell Dimension 4600, XP Home SP2, Pentium 4, 2400 MHz (18 x 133)
2048 MB (PC2700 DDR SDRAM)
Disk Drives:
Maxtor 6E040L0 (40 GB, 7200 RPM, Ultra-ATA/133)
WDC WD1200SB-01KBA0 (111 GB, IDE)
Optical Drive: NEC DVD_RW ND-3540A (DVD+R9:8x, DVD-R9:4x,
DVD+RW:16x/8x, DVD-RW:16x/6x, DVD-ROM:16x, 48x/32x/48xDVD+RW/DVD-RW)
Video: NVIDIA GeForce4 MX 440 with AGP8X (64 MB)
Sound: Creative SB0350 Audigy 2 ZS Platinum


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## BranSys (Apr 25, 2008)

My Computer:
Dell Dimension 4600i, XP Home SP2, Pentium 4 3.00GHz HT.

If you want to suppress the "Press F1 to continue. Press F2 to enter set up." message after the "Alert! Previous fan failure." message then press F2 to enter set up, scroll down and highlight "Report Keyboard Errors" and press the spacebar to change this setting from "Report" to "Do Not Report". After applying this change, the failure message will briefly appear and the boot will continue without any operator intervention required.

This is fine if you have verified that the CPU fan is operating correctly or you have replaced the fan with a non-Dell type and the system simply isn't detecting the presence of the new fan. However, if you start to see this message, don't ignore it as a genuine CPU fan failure will eventually lead to an overheat if it is relying on the heatsink alone to keep it cool.

I recently replaced the fan on my Dimension 4600i as it was sounding like a vacuum cleaner most of the time, and had done so since the system was new in 2004. I wanted to connect the new CPU fan to the motherboard CPU fan header in order to enable the system to detect the presence of the fan and prevent the "Alert!" error message. As the standard 3-pin connector on the new CPU fan was not compatible with the original Dell fan connector, I cut the lead off the original Dell fan and joined it to the lead on the new CPU fan with a terminal connector block. I originally connected the 3 wires thus: 1) white-yellow(TAC); 2) red-red(PWR); 3) black-black(GND). The fan worked but the system was not sensing its presence and still generated the "Alert!" error message. By doing a little research I determined that I needed to connect the white-yellow(TAC) wires to the black(GND) wires on the terminal block to enable the system to sense the presence of the fan. On restart, the CPU fan was running correctly and the system no longer generated the "Alert!" error message as it was now sensing the presence of the CPU fan.


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## BranSys (Apr 25, 2008)

BranSys said:


> I determined that I needed to connect the white-yellow(TAC) wires to the black(GND) wires on the terminal block to enable the system to sense the presence of the fan. On restart, the CPU fan was running correctly and the system no longer generated the "Alert!" error message as it was now sensing the presence of the CPU fan.


Connecting TAC to GND has disabled CPU fan speed sensing so the system will no longer warn of a fan failure - only of a disconnection of the fan connector from the fan header on the motherboard. As the CPU fan is no longer being automatically monitored, it would be wise to carry out a regular manual inspection of the fan to ensure it is working properly.


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## anon_lynx (Jul 20, 2008)

Thank you guys for the tip. I have made a nice post of it at 

http://www.dellcommunity.com/supportforums/board/message?board.id=dim_upghw&message.id=135061&jump=true#M135061

I am so glad to be free from the tyranny of DELL OEM replacement products.

When Bransys said he grounded Pin3 (yellow/sensor) I was concerned about current and thermal run-away so I did some experiments. I found that when Pin3 (+10.2 VDC) is grounded the circuit draws no current and the motherboard instantly senses the ground and drops the signal.

FYI

After more research I found a fellow (osprey4) on another board http://www.techimo.com/forum/technical-support/207178-cpu-fan-failure.html who says his son determined the circuit is for a heat-sensor within the fan.


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## BranSys (Apr 25, 2008)

I understand concerns regarding this workaround. I can, however, report that my system has been running for six months with this modification and I have not encountered any adverse side-effects. A replacement fan can simply be attached to a spare 4-pin Molex on the PSU, avoiding the CPU fan header on the motherboard. The fan warning message can be (partially) suppressed my making the change in the BIOS as I suggested in my previous post. As the replacement fan is not being monitored by the system, I would reiterate the importance of an occasional manual inspection of the fan, as part of a maintenance schedule to remove dust accumulation, etc. I have replaced the noisy, thermistor-controlled variable speed rear exhaust fan, shroud and passive heatsink combination with a fixed speed CPU fan-on-heatsink combination and a separate, fixed speed and quieter rear exhaust fan. This cooling set-up is working well despite the rather hot (by current standards) Prescott core P4 3.00GHz HT CPU!


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