Pinpoint Test I: The Auxiliary Blower Motor Is Inoperative

WARNING: This page is about a different car, the 2005 Ford RV Cutaway, 2005 Ford Econoline, 2005 Ford E450 Super Duty, and 2005 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

I1 CHECK FOR VOLTAGE TO THE AUXILIARY BLOWER MOTOR
- Key in OFF position.
- Disconnect: Auxiliary Blower Motor C4106.
- Key in ON position.
- Set the function selector switch in the FLR position.
- Set the auxiliary blower motor switch in the HI position.
- Measure the voltage between auxiliary blower motor C4106-2, circuit 371 (PK/WH) and ground.
  
  Fig 1: Checking For Voltage To Blower Motor
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes : GO to I2.
- No : GO to I4.
I2 CHECK CIRCUIT 261 (OG/BK) FOR GROUND
- Measure the resistance between auxiliary blower motor C4106-1, circuit 261 (OG/BK) and ground.
  
  Fig 2: Measuring Resistance Between A/C Blower Motor Connector And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : INSTALL a new auxiliary blower motor relay. TEST the system for normal operation.
- No : GO to I3.
I3 CHECK CIRCUIT 261 (OG/BK) FOR AN OPEN
- Measure the resistance between auxiliary blower motor C4106-1, circuit 261 (OG/BK) and the auxiliary high speed blower motor relay socket pin 30, circuit 261 (OG/BK).
  
  Fig 3: Measuring Resistance Between Auxiliary Blower Motor And Auxiliary High Speed Blower Motor
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : CARRY OUT the relay test on the auxiliary high speed blower relay. If the relay tests good, REPAIR circuit 57 (BK). TEST the system for normal operation.
- No : REPAIR circuit 261 (OG/BK) for an open. TEST the system for normal operation.
I4 CHECK CIRCUIT 884 (YE/BK) FOR VOLTAGE
- Key in OFF position.
- Disconnect: Auxiliary Blower Motor Relay.
- Measure the voltage between auxiliary blower motor relay socket pin 30, circuit 884 (YE/BK) and ground.
  
  Fig 4: Measuring Voltage Between Relay Socket And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes : GO to I5.
- No : VERIFY the battery junction box (BJB) fuse 14 (50A) is OK. If OK, REPAIR circuit 884 (YE/BK) for an open. TEST the system for normal operation.
I5 CHECK CIRCUIT 753 (YE/RD) FOR VOLTAGE
- Measure the voltage between auxiliary blower motor relay socket pin 85, circuit 753 (YE/RD) and ground.
  
  Fig 5: Measuring Voltage Between Auxiliary Blower Motor Relay Socket And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts.
- Yes : GO to I7.
- No : GO to I6.
I6 CHECK CIRCUIT 753 (YE/RD) FOR AN OPEN
- Key in OFF position.
- Measure the resistance between auxiliary blower motor relay socket pin 85, circuit 753 (YE/RD) and function selector switch C294a-2, circuit 753 (YE/RD).
  
  Fig 6: Measuring Resistance Between Auxiliary Blower Motor Relay Socket And Function Selector Switch
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : INSTALL a new function selector switch. TEST the system for normal operation.
- No : REPAIR circuit 753 (YE/RD) for an open. TEST the system for normal operation.
I7 CHECK CIRCUIT 57 (BK) FOR AN OPEN
- Key in OFF position.
- Measure the resistance between auxiliary blower motor relay socket pin 86, circuit 57 (BK) and ground.
  
  Fig 7: Measuring Resistance Between Auxiliary Blower Motor Relay And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : CARRY OUT the relay test on the auxiliary blower relay. If the relay tests good, REPAIR circuit 371 (PK/WH). TEST the system for normal operation.
- No : REPAIR circuit 57 (BK) for an open. TEST the system for normal operation.