Chevrolet Repair: HEATER FAN, resistor pack, purple wire

Question
I HAVE A 1990 S-10 BLAZER 4X4 WHEN I TURN ON THE HEAT OR A/C SOMETIMES THE BLOWER WILL COME ON OTHER TIMES WILL NOT BLOW ANY AIR. IS THE SOMETHING THAT CAN BE CAUSEING IT NOT TO RUN AT TIMES OR IS IT THE BLOWER MOTOR AND HOW TOUGH IS IT TO CHANGE THE BLOWER  

Answer
The blower motor itself would be a good guess, but there is a resistor pack, two relays, and a switch and controller that could also be the problem.
Next time it is turned on but not running, find the motor, and see if there is power to the wire to it...probably a purple wire.
Some of the S models, in order to replace the resistor pack, you need to cut a section of the blower housing out, so a manual with a cutting diagram is a must, and it will give you a troubleshooting proceedure also.
You can read one at the public library, in the refference section.

Van