My blazer no longer blows cold air and it only works on the highest two setting. I think it may have something to do with the blower moteor but I sm not to sure. Any help aould be great. Thanks!

no longer blows cold air?

If only the high speed works, check your HTR A/C fuse. If the blower switch has other speeds which no longer work, I would first check at the blower motor resistor. Low speed would be the brown wire, 2 = tan, 3 = light blue and high goes directly from the switch to the blower relay. Dark blue on the resistor goes through the relay to the motor. If you have power on the wires corresponding to their speeds, then the resistor is probably bad. If your missing power at them, check your switch.