PWM radiator fan controller

[1989GTA]

I have the Derale hooked up to a high amp relay, tripped by a timer relay for off. The Derale doesn't use a switched igntion, the relay does that for me (switched ignition). It is set for 90 seconds , it kills the power to it so they don't flutter on and off due to circulation.

I was thinking of doing that. A year or so ago I sent Derale and email regarding that subject and the response I got back was that I was crazy and did not know what I was doing. I thought that was an interesting response. Where did you install the probe in the radiator?