my 2000 dodge ram the heater blower motor will only run on the high setting why? on 2000 Dodge Ram 1500

I recently purchased this 2000 Dodge Ram 1500 V8 Magnum. This truck has become a headache 4 me the heater core was bad. the dashboard crumbled when I removed it to replace the heater core then 3 out of 5 lug-nuts and studs just broke off not a clue why. Now the heater blower fan is my latest project. It will only run at the highest setting. This is my first D0dge vehicle ever (never owned a Dodge truck ,car ,ect.any suggetiouns would be greatly appreciated

3 answers 1 comment
Blower motor resistor on passenger side firewall needs to be replaced. Two screws and a wire connector, five minuet job!
I agree with wetry
Blower motor resistor needs replaced.
blower motor resistor is bad.should be on outside of heater box under glove compartment