1998 Astro Trouble

I have a 1995 plymouth neon, my blower motor quit yesterday. Fuses were good, I unplugged the connection from the motor and put it on the battery and the motor worked. I plugged it back in and grounded the negative wire from the motor to a screw on the dash and the motor worked but only full speed. On the climate control it seems that the temp selector works and the switch from heat to ac to vent ect. works, all except the fan speed control. Do you think the speed control is bad or did I loose ground somewhere else. If it's somewhere else, where can I look? Thanks, Joe

99 Intrepid The blower fan stopped working on the first, second, and third speed but would still work on the high forth speed. I replaced the resistor block and all speeds worked again. About 4 days later the same thing happened and I need another resistor block. I played with the original one that burnt out and I had a hard time to figure out how it works. It has 3 coils of different sizes and those put the resistance in the circuit for the first 3 low speeds. It also has a small electronic device that is the piece that is burnt out and will not allow current to the low speeds. My question is: What is this device? My guess it would read temperature and stop the blower motor until the air was a certain temperature until it allowed the blower to turn on when in the heater mode. We just got the car so I am unsure how the heater normally works. Am I right in my assumption here. Can I bypass this device until I get another blower in? Thanks