Mobo does not detect CPU fan speed.

[Captain Colonoscopy]

Seeking some input. I swapped out a stock HSF on a customer's pc with an Artic Cooling 2L rev 2. The BIOS does not detect the fan's RPMs even though it is plugged in correctly. The box would shut off after a while because of this so I plugged one of the case fans into the CPU fan header so I could get the damn thing to stay on. So, the question: Is there anyway to fix the monitoring function on a fan or should I just send the HSF back to SVC and get a different one? I was kind of hoping to avoid another two weeks of waiting for crap in the mail.

Thankies.