Networking Equipment Fan Controller Issue

Hi all,

I was working on replacing some fans within a network switch and believe I overloaded or shorted something when connecting the new fans. A puff of smoke and now all fan control has gone. Now I've got one fan connector running a fan at full speed and the other connector (the one I overloaded) with no response, swapping the fans over and all is the same so the fans are okay.

You can see in the images some burn marks around the surface mounted 2ohm resistor and IC. I'm assuming that either that IC or resistor has failed.

More info:

Working fan connector, albeit uncontrolled (looking from above, left to right)

• Pin 1 - No connection to earth - 11.72v
• Pin 2 - No connection to earth - 0.6v
• Pin 3 - Connection to earth - 0.6v

Dead fan connector

• Pin 1 - No connection to earth - 11.72v
• Pin 2 - No connection to earth - 10.4v
• Pin 3 - No connection to earth - 10.4v

Continuity tested with device off. With the switch powered up none of the pins appear to be connected to earth (ground).

I've attached some photos of the fan circuit. The IC in question appears to have M3214S 40110G on it but Googling brings up nothing. If I could find a datasheet on it maybe it would be easy to figure if it's functioning correctly? Tricky to tell if the resistor is dead with it still in situ. I've now exhausted my basic electronics knowledge and need a little support on the direction I should take.

Thanks all!