The blower fan cuts out intermitently regardless of fan speed when I go over a bump or take a corner. The dash had been removed to replace the evaporator and this is when the problem started. When the fan blows I have no problem with the auto ac controls and I get all speeds. Do resistor packs go out intermitently like this or the fan moter? Or is this a gounding issue?

SOURCE: Heater/AC blower will not operate

Replace the blower resistor.

SOURCE: 2002 Chevy Impala Blower resistor location

It is on the passenger side, you have to remove the black plastic kick plate, below the glove box, to expose it (held in place with 2 latches and 1 push pin). The resistor is in front of the blower motor ( sandwiched between the motor housing and the firewall) it is tricky to get to, i think when i changed mine i didnt replace all the screws as they were difficult to remove and even harder to replace. Good Luck, Mike

SOURCE: Blower motor resistor

I believe it's behind the glove box. Once you remove the glove box it's easy to get to. Hope this helps.

SOURCE: Blower motor vent selection switch not working

the hvac selector switch in the dash may be the problem.You need to remove the switch and look at the connector on the back of switch,see if there are any burnt wires at the connector or switch.It's all electronic and the switches have been known to burn out on this and other model.

SOURCE: how do I replace the front blower resistor pack

It is located just left (towards the driver side) of the blower motor base. The motor base is on the passenger side under the glove box and is round in shape. Disconnect the wire connector. Remove the two screws that hold the blower resistor into the blower assembly. You may need a short phillips head screwdriver to do this. A standard length screwdriver may be too long and interfere with the sloping foot well at this point.