PWM cooling fan(s) control using ECM

[carbuff]

Question of ignorance here, looking for a little education...

Can you use a PWM fan controller on any cooling fan, or does the fan need to be designed to handle the fast on/off switch of the PWM? In other words, would you burn-out a normal fan if using a PWM controller on it?

I haven't looked, but I'm now wondering if anyone makes an aftermarket PWM fan controller. I think the idea here is interesting, but at least from the GM implementation, it's not just a simple aftermarket conversion...