blower fan

I have an '02 S10 with the 4.3L. This morning I started driving and went to turn on the blower fan. Keep in mind it was only 17 degrees at my place. Anyway, as soon as I turned it on, the lights dimmed and the voltage meter went down for a moment. The blower didn't even turn on. I drove it for about 5 miles and things started to work again except I can't get the HI level to work. The fan will turn off. Any ideas as to what the problem may be?



Thanks!!!

Check the resistance from the black wire on the blower to ground, should be less than 5 ohms. Connect a fused jumper wire from battery positive to the purple wire on the blower motor, it should run at full speed. If not, replace the blower motor. If those two things check OK, here's more for you to check:
Locate the high blower relay, it is mounted to the heater housing under the hood. The high blower relay has 2 orange wires. The larger one should be HOT at all times. The smaller one comes from the fan switch in the high speed position and should be HOT when the ignition is in the RUN position and the fan switch is in the HIGH speed position. The black wire should be less than 5 ohms resistance to ground. The purple wire goes to the blower motor. The dark blue wire comes from the blower resistor and carries speeds 1, 2, and 3. Check it out and post your results.