Radiator and A/C Condenser Fan Low Speed Circuit Troubleshooting

WARNING: This page is about a different car, the 2013 Acura MDX, 2012 Acura MDX, 2011 Acura MDX, and 2010 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

Do not use this troubleshooting procedure if the A/C compressor is inoperative. Refer to the SYMPTOM TROUBLESHOOTING INDEX .
Before performing symptom troubleshooting, check for powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION ).

Check the No. 15 (30 A) fuse in the relay block, and the No. 30 (10 A) fuse in the under-dash fuse/relay box.
Are the fuses OK?

YES -Go to step 2.

NO -Replace the fuse(s), and recheck. If the fuse(s) blow again, check for a short in the No. 15 (30 A) and No. 30 (10 A) fuse(s) circuit.
Remove the A/C condenser fan relay and fan control relay from the relay block, and test it (see POWER RELAY TEST ).
Are the relay OK?

YES -Go to step 3.

NO -Replace the faulty relay.
Connect the HDS to the DLC.
Turn the ignition switch to ON (II).
Turn on the A/C.
Check the FAN LOW CTRL in the PGM-FI Data List with the HDS.
Is the FAN LOW CTRL on?

YES -Go to step 7.

NO -Substitute a known-good PCM (see SUBSTITUTING THE PCM ), and retest. If the symptom/indication goes away with a known-good PCM, replace the original PCM (see PCM REPLACEMENT ).
Set the A/C button and fan control button OFF, then turn the ignition switch to LOCK (0).
Measure the voltage between A/C condenser fan relay 4P socket terminal No. 1 and body ground.

Fig 1: Measuring Voltage Between A/C Condenser Fan Relay 4P Socket Terminal No. 1 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Go to step 9.

NO -Replace the under-hood fuse/relay box (see DTC B1065: RELAY CONTROL MODULE LOST COMMUNICATION WITH DRIVER'S MPCS UNIT (DRLOCKSW MESSAGE) ).
Connect the A/C condenser fan relay 4P socket terminals No. 1 and No. 2 with a jumper wire.

Fig 2: Connecting A/C Condenser Fan Relay 4P Socket Terminals No. 1 And No. 2 With Jumper Wire
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Do the A/C condenser and radiator fans run on low?

YES -Go to step 10.

NO -Go to step 19.
Disconnect the jumper wire.
Turn the ignition switch to ON (II).
Measure the voltage between A/C condenser fan relay 4P socket terminal No. 4 and body ground.

Fig 3: Measuring Voltage Between A/C Condenser Fan Relay 4P Socket Terminal No. 4 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Go to step 13.

NO -Go to step 32.
Turn the ignition switch to LOCK (0).
Reinstall the A/C condenser fan relay.
Jump the SCS line with the HDS.
NOTE: This step must be done to protect the powertrain control module (PCM) from damage.
Disconnect PCM connector A (49P).
Connect PCM connector A (49P) terminal No. 4 to body ground with a jumper wire.

Fig 4: Connecting PCM Connector A (49P) Terminal No. 4 To Body Ground With Jumper Wire
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Turn the ignition switch to ON (II).
Do the A/C condenser and radiator fans run on low?

YES -Check for loose wires or poor connections at PCM connector A (49P) terminal No. 4. If the connections are good, substitute a known-good PCM (see SUBSTITUTING THE PCM ), and recheck. If the symptom/indication goes away, replace the original PCM(see PCM REPLACEMENT ).

NO -Repair an open in the wire between the A/C condenser fan relay and the PCM.
Disconnect the jumper wire.
Reinstall the A/C condenser fan relay.
Disconnect the A/C condenser fan motor 2P connector.
Turn the ignition switch to ON (II), then set the A/C button and fan control button ON.
Measure the voltage between A/C condenser fan motor 2P connector terminal No. 2 and body ground.

Fig 5: Measuring Voltage Between A/C Condenser Fan Motor 2P Connector Terminal No. 2 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Go to step 24.

NO -Repair an open in the wire between the A/C condenser fan relay and the A/C condenser fan motor.
Set the A/C button and fan control button OFF, then turn the ignition switch to LOCK (0).
Test the radiator fan motor and A/C condenser fan motor (see FAN MOTOR TEST ).
Are the motor OK?

YES -Go to step 26.

NO -Replace the faulty fan motor.
Turn the ignition switch to ON (II), then set the A/C button and fan control button ON.
Measure the voltage between fan control relay 5P socket terminal No. 1 and body ground.

Fig 6: Measuring Voltage Between Fan Control Relay 5P Socket Terminal No. 1 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Go to step 28.

NO -Repair an open in the wire between the A/C condenser fan and the fan control relay.
Set the A/C button and fan control button OFF, then turn the ignition switch to LOCK (0).
Disconnect the radiator fan motor 2P connector.
Check for continuity between fan control relay 5P socket terminal No. 4 and radiator fan motor 2P connector terminal No. 2.

Fig 7: Checking For Continuity Between Fan Control Relay 5P Socket Terminal No. 4 And Radiator Fan Motor 2P Connector Terminal No. 2
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 31.

NO -Repair an open in the wire between the fan control relay and the radiator fan.
Check for continuity between radiator fan motor 2P connector terminal No. 1 and body ground.

Fig 8: Checking For Continuity Between Radiator Fan Motor 2P Connector Terminal No. 1 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Replace the radiator fan motor.

NO -Check for an open in the wire between the radiator fan and body ground. If the wire is OK, check for poor ground at G301 (see CONNECTOR TO FUSE/RELAY BOX INDEX ).
Turn the ignition switch to LOCK (0).
Remove A/C diode A from the relay block.
Using the diode setting ( ) on a DVOM, check for current flow in both directions between A/C diode A terminals No. 1 and No. 2.

Fig 9: Checking For Current Flow In Both Directions Between A/C Diode A Terminals No. 1 And No. 2
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there current flow in only one direction?

YES -Go to step 35.

NO -Replace A/C diode A.
Turn the ignition switch to ON (II).
Measure the voltage between A/C diode A 2P socket terminal No. 2 and body ground.

Fig 10: Measuring Voltage Between A/C Diode A 2P Socket Terminal No. 2 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Replace the under-hood fuse/relay box (see DTC B1065: RELAY CONTROL MODULE LOST COMMUNICATION WITH DRIVER'S MPCS UNIT (DRLOCKSW MESSAGE) ).

NO -Repair an open in the wire between the No. 30 (10 A) fuse in the under-dash fuse/relay box and A/C diode A.