Subido por jmc.jurado

Dell Dimension 4600i

Dell Dimension 4600i
I have a Dell Dimension 4600i and received the same "Alert! Previous fan failure"
message after I replaced the original Dell single fan cooling system with a two-fan
system (92mm exhaust fan on the rear of the case and a CPU fan and heatsink
combination). The original Dell design is very noisy as it employs a single 92mm fan
mounted on the rear of the case which draws air through a green plastic shroud
mounted over a large passive copper heatsink on the CPU. You can obtain a
compatible 92mm rear mounted replacement fan on eBay (search for DELL
DIMENSION 4600 FAN) but it will be just a noisy as the original. If you can put up
with the noise, then this will be the simplest option. If you want to replace your
existing cooling setup with a quieter one, these are the parts I fitted about a month
ago and are working well (I have an Intel P4 3.00GHz Hyperthreading HT Socket
478 Prescott CPU - I am in the UK so prices are in GBP with approximation for
Xilence Red Wing 92mm Quiet Fan - 3&4 pin connection. Mfr: Xilence, Part #:
XILENCE92 (4.73GBP/9.46USD -
Akasa Intel Socket 478 P4 3.4GHz Extreme Edition Copper base Aluminium Fin
Processor Cooler. Mfr: Akasa, Part #: AK-687A (9.99GBP/19.98USD -
CPU Heatsink retention bracket SOCKET 478 (3.24GBP/6.48USD -
Terminal connector block (3-terminals) to connect the new CPU fan to the original
Dell fan connector (0.99GBP/1.98USD - any DIY store)
The websites are UK-based, but will give you detailed descriptions of the
components even if you don't order from them.
Unfortunately, Dell doesn't make life easy for you. You will need to replace the CPU
heatsink retention bracket as the original will not be compatible with the new
processor cooler. This will involve removing the motherboard, as the original CPU
heatsink retention bracket is screwed into 4 risers which are, in turn, screwed into
the backplate behind the motherboard. The risers need to be removed or the
retaining pins for the replacement CPU heatsink retention bracket will not fit. You
could avoid removing the motherboard and the 4 risers by drilling-out the 4
mounting points in the replacement CPU heatsink retention bracket and using the
existing 4 retention bracket mounting screws. This would require some care as the
retention bracket is made of a fairly flimsy plastic and could easily shatter. Be very
careful when removing the original heatsink. You need to release the 2 green plastic
retaining clips first. Then gently twist the heatsink clockwise/anticlockwise a couple
of degrees first before carefully pulling it out. It will most probably be stuck to the top
of the CPU by the thermal interface material between the top of the CPU and the
bottom of the heatsink. This is best done when the CPU is warm - so run the
machine for a few minutes before removal. Carefully clean the top of the CPU with
pure isopropyl alcohol to remove the old interface material. The new heatsink
usually has thermal interface material pre-applied.
You will also discover that the 3-pin CPU fan header on the motherboard is not
compatible with the 3-pin connector on the new CPU fan. You will need to cut the
connectors off the original Dell fan and the new CPU heatsink fan and join the 3
wires of the new fan to the 3 wires of the original Dell fan connector with 3 terminals
of a terminal connector block. The wires are connected thus: T1)
White-Yellow(Tachometer); T2) Red-Red(+12V DC Power); T3)
Black-Black(Ground). You can then plug the original Dell fan connector into the
CPU fan header on the motherboard. You can solder the wires of the new CPU fan
directly onto the pins of the original Dell fan connector plug by extracting the tiny
pins from the plastic surround; but this is an extremely fiddly process in which you
risk breaking the original connector. I found that simply cutting and splicing the wires
together with a terminal connector block was far easier. You could also connect the
CPU fan directly to a spare 4-pin molex power connector from the power supply unit
via a 3-pin fan to 4-pin molex adapter and bypass the CPU fan header on the
motherboard altogether. In this case, you will continue to receive the "Alert!
Previous fan failure" message as the CPU fan's tachometer line will not be
I found that with the Akasa CPU fan connected to the CPU fan header on the
motherboard I was receiving an intermittent "Alert! Previous fan failure" message on
boot. You may be lucky and not see this message. It would appear that the fan's
tachometer is sending a signal that is regarded as just outside what the Dell
motherboard regards as normal. The only way to ensure this message doesn't
appear is to fit an official Dell replacement fan as I mentioned above. There are
three ways to deal with this message. 1) Ignore it and press F1 to continue the boot
process; 2) 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; 3) Ground the tachometer wire by connecting the
White-Yellow(Tachometer) wires to the Black-Black(Ground) wires on the terminal
connector block. This will disable CPU fan speed sensing so the system will no
longer warn of a fan failure and no longer display the "Alert! Previous fan failure"
message - this will now only appear if the fan connector becomes disconnected
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. Grounding the tachometer wire has worked
for my particular hardware setup, but is probably not generally recommended. In
any event don't short circuit the Red-Red(+12V DC Power) terminal as this could
destroy your system!
Don't ignore the "Alert! Previous fan failure" message as this could eventually lead
to an overheat of your CPU.
Need Help: "previous fan failure" on start up