Test this way:
BLOWER OPERATES AT HIGH SPEED ONLY 1. Check Blower Motor Operation Ensure ignition is on. Set A/C blend door control to FLOOR position. Set blower motor switch to LO position. If blower does not operate, go to step next step. If blower operates, go to step 5). 2. Check Blower Switch Positions Slowly rotate blower motor switch knob from LO to HI. Check blower operation at each detent. If blower does not operate at each detent, go to next step. If blower operates at each detent, go to step 4). 3. Check Ground Circuit Check Black wire between blower switch and blower motor resistor for open circuit. Repair as necessary. If wire is okay, replace blower motor resistor. 4. Check Circuit Check Orange/Black wire between blower switch and blower motor resistor for open circuit. Repair as necessary. If wire is okay, replace blower motor resistor. 5. Check Blower Switch Check blower motor operation in each position. If blower motor does not operate in each position, go to next step. If blower works in each position, recheck A/C system operation in all functions and blower speeds. Instruct owner in proper system operation. 6. Check Blower Switch Continuity Check continuity of blower switch in indicated positions. See BLOWER SWITCH TEST table under NO BLOWER OPERATION AT HIGH SETTING. See Fig. 1 . If continuity is not as specified, replace blower motor switch. If continuity is as specified, Repair open Black wire between blower motor switch and ground.