I bought a 217 CFM PC fan for my new vivarium setup but when it came it has 3 wires instead of two. What is the 3rd wire for? Can I run the fan just using the red and black hooked to a 12V wall wart as usual or does the yellow wire (or is it blue) have to go somewhere? I've wired up a few two wire fans before but never messed with a 3 wire one.
I got an awesome lot of 10x two wire/12V 3" 32 CFM fans for $1.39 each off evilbay for use as tank to tank airflow and lamp heat extraction on the new vivariums I'm planning, but this was to be my main workhorse input fan for the whole rack. I'd hate to think it's essentially "useless".