x61 fan error

[richk]

I have an X61 (T8300 CPU) with a "fan error" at startup. The fan does spin and the machine will run if you hit ESC. Using google, I found many references to the problem, but no solutions. Most of the posts talked about having the second fan. (so does mine) I tried a second main fan, but there was no change. The secondary fan also spins for 1/2 second at startup, so I hesitate to go out and buy a second fan hoping a miracle will occur and a new secondary fan will correct the problem. None of the other posts suggested that a secondary fan replacement would help. I did try replacing the MOSFET I think is involved in the primary fan circuitry from a junk board and all I can say is I didn't make it any worse. Any suggestions?

[EOMtp]

The secondary fan also spins for 1/2 second at startup, so I hesitate to go out and buy a second fan hoping a miracle will occur and a new secondary fan will correct the problem.

It sounds like you have eliminated the primary fan from suspicion, but the secondary fan might still be suspect. I bet it's the secondary fan! Even though it spins, its tachometer pulses are not reaching the motherboard.

Temporarily wire the secondary fan's connector to a known good fan with a similar voltage rating, connect that fan to the secondary fan connector on the motherboard, and see if the problem is resolved.

If yes, then the culprit is the secondary fan or its wires; if no, then the problem is unrelated to the fans themselves, and ... (clearly, you know the rest of the drill!)

Good luck!

[richk]

Thanks for the suggestion, but I already hooked a working fan up to the secondary connector. It spun for 1/2 second at startup then stopped. (just like the one that was there to start with) (I wasn't sure what kind of fan to try, but they all seem to be 5 volts, so I used one out of a T61, which has the same connector.)

There is a transistor connected to the fan lead that isn't fused and isn't ground. I assume that one switches sensing pulses. I may swap that one also. (It's free to try) I cannot see much on the second fan circuitry. The thing is sitting on a socket that is glued to the motherboard. The relevant parts appear to be under the socket.

[k330]

open fan Add a little grease
a little