I recently bought a 3 pin fan splitter, and one of the leads has a 3 pin connector, but the other one only has 2. I am wondering if a fan will work on the 2 pin connector. It looks like one of the pins was knocked out intentionally, and not like it was a defect.
AFAIK motherboard will read RPM info from the first fan(with 3 pins). Third pin sends the RPM of the fan. Other fans will work fine, because speed depends on voltage and current.