I installed some aftermarket fans a few years ago. They used a thermostatic snap switch that was attached to one of the lower cooling tubes near the heating unit. They were attached with 1/2 inch wide strapping tape - the kind with strong threads in it used for taping up boxes. Just laid the switch on the tube and wrapped the tape around it and the switch unit. Worked for two years til I replaced the cooling with the Amish unit and new fans. (By the way, that was the smartest move I've made in a while.)
