Dodge Ram 1500 Fan Electrical

It's the blower motor reistors, there located under the instrument panel on the passenger side by the the blower motor. Disconnect the electrical connector from the blower resistor. Remove the screws and withdraw the resistor from the housing. To check these just use a continuity tester on the resistor, check between each input terminal starting from the blower speed switch side (of the resistor) to the output terminal to the blower (of the resistor). There sould be continuity (a closed circuit or a complete path for current flow) on any combination of the four terminals. If not then replace the blower motor resistor with new ones.
If this does not work then check the fuse and all connections in the circuit for looseness and corrosion.