Review on Derale 16738 Single Stage Electric Fan Controller, Black - 180°F Temperature Control by Kevin Bucher

I've used a couple of adjustable thermostat switches that die in a year or two. Always off the beaten track! I switched to this style which is off/on. I hope the fragile electronics don't fail. Turns on at about 190 and stops at 180 which I believe is the result of a temperature difference where it's only sticking through the heatsink and not making direct contact with the liquid. Update: Recently returned from the Hot Rod Power Tour and this fan switch/relay worked with no problems. The weather was very hot and we drove 3300 miles. I would say it works as advertised.