The problem is more likely the blower motor resistor. Especially if it lost speeds at different times. You can access the blower motor resistor from under the dash. You will also likely find that the connector has melted into the resistor. GM makes a replacement pigtail that you can splice in. I've done a lot of these! I always put dielectric grease in the connector before reinstalling. If there are ANY signs of the connector melting or the terminals are not shiny then replace the resistor and the connector or you will continue to have problems.