I have a question about replacing the case fan in a Dell 4550, and hope someone can shed some light on how it works. I searched a bit, but didn't really find anything describing my problem

After my PC shutdown with the, "Fan not working, press F1 screen on reboot", I found the case fan would not spin up when connected to a small 12 volt battery. At the store the guy said, "Oh a Dell", and offered me a used 92mm fan he said came from a Dell with the same 3 pin connector. He tried it and it spun, and tried mine which did not. For a few bucks I walked away, tried the same 12 volt battery check at home and indeed it did work.

The question;

I know there is that white wire as well as the sensor on both new and old fans and the wires are in the same positions on both 3 pin connectors. When I connect it, and try to boot, the fan does not spin. I did see just under 12 volts at the connector on the board, so it is getting power.

I am wondering if the sensor plays a part in causing the fan to turn on? Does it need to register a certain heat, to run, or is there some other kick on or kick off point I am overlooking. From what I've read the white wire is an r.p.m. indicator, but I would think the on fan sensor would be for heat.

If memory serves me, the old fan would run as soon as I flipped the PC's on switch.

Many thanks. I know I'm not here much, but have little solid to offer. Often the quality help you give each other is a bit over my head.

9 Years
Discussion Span
Last Post by ATF

Resolved! My stupid! The plastic connector between the 3 wires off the motherboard and the snap in female tip on the fan wires, was just a bit pulled out, so that it did not make contact. I thought it was a hard push back on, but found a wiggle back and forth pushed it in a fraction more so that it made contact.

I have big hands and it was a bit of a reach for me to pull off when I first removed the fan, so I did pull on it slightly when trying to reach for the release catch. :D

Many thanks friends. :)

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