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Climate Control Pinpoint Test 8: Blower Motor Operates Continuously In High Speed

CLIMATE CONTROL PINPOINT TEST 8 CHART - BLOWER MOTOR OPERATES CONTINUOUSLY IN HIGH SPEED

PINPOINT TEST 8 BLOWER MOTOR OPERATES CONTINUOUSLY IN HIGH SPEED
STEP INSPECTION ACTION
1 CHECK THE BLOWER MOTOR SWITCH
  • Key OFF.
  • Disconnect the function selector switch 4-pin electrical connector 0740-102 for blower motor switch.
  • With the function selector switch set in each position, measure the resistance between the function selector switch pins, component side. See the chart below this test.
  • Are the resistances less than 5 ohms when continuity is expected and greater than 10,000 ohms for all others? 
 Yes Go to step 2.
No Install a function selector switch. Test the system for normal operation.
2 CHECK THE BLOWER MOTOR RESISTOR
  • Disconnect the blower motor resistor.
  • Measure the resistance between the blower motor resistor pins, component side. See the chart below this test.
  • Are the resistances as indicated? 
 Yes Go to step 3.
No Install a new blower motor resistor. Test the system for normal operation.
3 CHECK CIRCUIT (O/B) FOR AN OPEN
  • Measure the resistance between the blower motor resistor 0740-105 pin 4, (O/B) and the function selector switch 0740-102 pin 1, (O/B).
  • Is the resistance less than 5 ohms? 
 Yes Go to step 4.
No Repair circuit (O/B) for an open. Test the system for normal operation.
4 CHECK CIRCUIT (Y/R) FOR AN OPEN
  • Measure the resistance between the function selector switch 0740-102 pin 4 (Y/R) and the blower motor resistor 0740-105 pin 3 (Y/R).
  • Is the resistance less than 5 ohms? 
 Yes Go to step 5.
No Repair circuit (Y/R) for an open. Test the system for normal operation
5 CHECK CIRCUIT (LG/W) FOR AN OPEN
  • Measure the resistance between the function selector switch 0740-102 pin 2 (LG/W) and the blower motor resistor 0740-105 pin 1 (LG/W).
  • Is the resistance less than 5 ohms? 
 Yes Go to step 6.
No Repair circuit (LG/W) for an open. Test the system for normal operation.
6 CHECK CIRCUIT (O/B) FOR A SHORT TO GROUND
  • Measure the resistance between the function selector switch 0740-102 pin 1 (O/B) and ground.
  • Is the resistance greater than 10,000 ohms? 
 Yes Go to step 7.
No Repair circuit (O/B) for a short to ground. Test the system for normal operation.
7 CHECK CIRCUIT (Y/R) FOR A SHORT TO GROUND
  • Measure the resistance between the function selector switch 0740-102 pin 4 (Y/R) and ground.
  • Is the resistance greater than 10,000 ohms? 
 Yes Go to step 8.
No Repair circuit (Y/R) for a short to ground. Test the system for normal operation.
8 CHECK CIRCUIT (LG/W) FOR A SHORT TO GROUND
  • Measure the resistance between the function selector switch 0740-102 pin 2 circuit (LG/W) and ground.
  • Is the resistance greater than 10,000 ohms? 
 Yes Go to step 9.
No Repair circuit (LG/W) for a short to ground. Test the system for normal operation.
9 CHECK CIRCUIT (O/B) FOR A SHORT
  • Measure the resistance between function selector switch 0740-102 pin 1 circuit (O/B) and:
    • pin 4, circuit Y/R.
    • pin 2, circuit LG/W.
  • Are the resistances greater than 10,000 ohms? 
 Yes Repair the affected circuit(s). Test the system for normal operation.
No Repair circuit (O/B) for a short. Test the system for normal operation.
BLOWER SWITCH CHECK CHART

Switch Position Conductivity Between Terminals
Low None
Medium/Low 2 and 3 Only
Medium/High 2, 3, and 4 Only
High 1, 3 and 4 Only
BLOWER MOTOR RESISTOR CHECK CHART

Blower Motor Resistor Pins Conductivity Between Terminals
4 and 2 3,750 milliohms
4 and 1 1,050 milliohms
4 and 3 250 milliohms
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