Previa fan resistors are pretty solid, but even if it failed the blower would still work on high. Previas have weak fan switches, but when they fail it's usually only the med/high setting (max high and the lower settings will typically still work). My guess is it's a bad blower motor, but you should check the fuse/breaker 1st. Another test is to disconnect the motor input connector (2 position plug with one red wire & one blue wire going to it), then put 12vdc directly into the motor to see if it works. The blower motor is accessed from under the hood. It's not that terrible to replace. You need to remove the plastic intake air scoop, then the plastic box behind that. That box splits in half, and the blower motor is inside it. Tim

PS: I've seen this problem a couple times & both times it was a bad blower motor. They tend to fail at around 150k - 200k miles, but of course this will depend on your climate and how often and what speed you run the blower. It's been too many years since I did the job to remember more details than I posted...........I may even be wrong on thinking the entire housing needs to come out. You may be able to split the box while it's in place and change the motor then...............Just can't quite remember. Good luck. Tim