Hello. I have three computer fans that I'm trying to set up with a small transformer. Trouble is when I tried it on one the wire got hot and the fan didn't go anyway so I stopped. The Power pack is output 12V - 1200 mA. And the fans are all 12V 0.18A. Another question, if I put them in series it will lower the voltage and stop or slow them right? Do I have to wire them in parallel?
Thanks Guys :)

Make sure you have the proper converter. Some are AC and some DC, which must match the motors. . Always wire fans in parallel.