Review on Derale 16735 Farenheit Electric Controller by Allen Hart

My old Flex-lite Adjustable Temperature Controller (Part #FLX-31147) has expired after being connected to a Derale (DER-1627) for almost 10 years. A powerful 12 volt electric fan is on my old 4.0 V-6. After thinking I didn't really need an adjustment and wondering why I hadn't matched the Derale fan control box with my Derale fan, I concluded that this Derale 16735 fan control kit would be a well matched and logical replacement . I was wrong! For some reason it worked as advertised for about 2 test cycles (the engine ran until it got hot enough to turn on the fan); but the next day it failed (yes the fuse was still fine)? The only good news is that the air conditioner lockout feature works by turning the fan on with the air conditioner (like the old controller did). So back to the drawing board, but paying $40 for a defective sensor and/or switch is no good. 2 stars is generous.