blower motor?resistor?

[GAWKY]

I got a 97 SL and when i have the fan on it will occasionaly change speed by its self, I checked the voltage at the blower motor and in high speed I got normal readings, when i checked the voltage it was working fine though. Could this be the blower motor or resistor going out? or could it be the fan switch??
Thanks

[saturntech]

Does it do it on all speeds or just on high???

[GAWKY]

it does it at any speed, and all the speeds seem to blow at lower speeds than usually

[saturntech]

Well it wouldn't be the resistor, because if the resistor went then you would only have high since you don't need resistance in high speed