My attic variable speed fans regulator failed. I cannot find another one. It is hot. I hooked up the fan directly without a regulator.
Is it safe? Is it running at its lowest speed?
With as little as you have given us, I would say that the fan could run for years hooked up like that. The fan probably is running full-out without the regulator.
What are you calling a regulator anyway? What makes you think that it failed? The big-box stores sell attic vent fans all the time. Anyway, fans like this are designed to fail-safe, meaning that it is safe to operate with a shorted/open regulator.
Just remember to unhook the fan when fall/winter comes around.
The regulator might be a thermal switch. Mine are TRIAC-based with an adjustment knob. In this case, bypassing the controller means the fan is on high speed all the time, hot or cold. Only you can say if the fan is running at what seems like its fastest setting.