Thanks! Yes, very aware of how a fan clutch works (not saying that to sound like a jerk). The URO Parts fan does "slip" as one would expect it should. In other words, with the engine off, cold it can be spun by hand with minor resistance felt, and with the engine at 80*C/180*F, it still only has slight drag/resistance. So just in "testing" it that way, one would think it's functioning properly. However, in actual driving conditions, whether right after first cold start, and during the initial .8km/.5mi of driving, or after 30min to an hour of driving, it performs exactly the same, literally being so engaged that it roars all the time. The Behr clutch feels just like the URO Parts clutch, when just hand spinning it, either cold or hot, however, it is silent, as it should be, during normal driving.
I too have had poor results from aftermarket radiator fan clutches. I only purchased the URO Parts clutch because I couldn't find an OE at the time, and it was only $46.... so I was thinking: The car is just going to be driven around town, and short trips on the freeway, in mild/pleasant temps, so even a low priced (potentially low quality) clutch should be able to survive that. Oops.
I have a '90 GMC Suburban with clutched fan on a 5.7L/350ci V-8. That clutch gets a full workout, because I tow, in the mountains, and in the heat, at low speeds, as well as towing out across the desert in triple digit heat. When cold, that fan is fully engaged for about .8km/.5mi, indicating it's alive. Then it suddenly goes quiet, and the fan is not heard again, either until the next cold start, or until it gets so hot that the fan engages. It sounds like a diesel locomotive when it engages on the freeway