The a/c fan motor will not shut off. the fan adjustment bars are showing slower but still the fan is on high

the blower motor resister is bad. go to a mechianic and get it replaced

The fan speed reostat is broken or the switch itself is bad. Try replacing the switch first because the motor speed reostat is part of the motor itself. $$$

Visit the on-line store, known as reliable-store, they have the repair manuals. I'm sure you will get the solution of your problem.
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Your impala doesn't have a resistor , it has a blower motor control processor and it doesn't work the way you think it does
Chevy Trailblazer EXT Blower Motor Won Turn Off
Blower Motor Control Processor
The blower motor control processor is an interface between the HVAC control module and the blower motor. The blower motor speed control, battery positive voltage and ground circuits enable the control processor to operate. The HVAC control module provides a PWM signal to the control processor in order to command the blower motor speed. The processor supplies 12 volts to the blower motor through the blower motor voltage supply circuit. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.

HVAC Blower Motor Circuit

no high speed ? fan motor relay, no slower speeds resister pack.or faulty fan switch.
Check motor with jumper lead from battery,but unplug power lead to motor first. check grounding wire to motor. if motor dont run replace!

The high blower works off a relay in the high speed only so the fan switch is at fault on your vehicle
Replace the fan blower control speed switch which is the one you adjust the lower fan speeds

make sure that your fuel pump is rated for the same pressure as your carb. if you bought it as a package deal than it probably is but unlike fuel injected vehicles that have a pressure regulator the fuel is constant flow in a carb.

Well it sounds like the blower motor relay is out you might also need a blower motor if it is using to much juice on high speed then the blower motor is probabley about to go out and with the noise you are describing it sounds like a bearing in the blower motor is about to go out so probabley should change the blower motor and the blower motor relay.

I'm assuming you mean the fan only works on high. If that's the case the blower motor resistor is bad. When the fan switch is on high it puts a full 12Volts to the blower motor. When you have the switch in any other possition, the voltage is routed through the resistor and reduced thus making the motor run slower.

You don't...I mean you can't adjust the serpentine belt because there is automatic self tensioner which loaded by a very high compression spring. Now, there should be a square hole on the tensioner which is a 1/2 inch. You simply put a half inch breaker bar in the square hole to gain leverage in order to change your belt. Hopefully this helps