Fan for AC/heat

HELP!!! The blower motor only works on high for ac and heat, why does it only work on high, if the whole unit was defective shouldn't it not work at all.

I dont know if it the same but on my 2000 Silverado the fan wasnt working on the 1 & 2 speed read a post in the SILVERADO forum (Hvac 2 not working) or something like that. Recommended changing the blower motor resistor, whick was located near the blower. Did it myself for about 20 bucks for the part, now it works fine. If the Rodeo has the same kind of set up and I see why not, my 94 mustang did, the fix shouldnt be to bad.

Hope this helps

resistor is bust you can change just the resistor it wil work for a while and burn out again or you can replace the blower and resistor and all will be good
there is an alternative to replacing the resistor remove it break the plastic off of the sides of it and resolder the thing back together