Circuit/System Testing

Inoperative in All Speeds

1. Ignition OFF, disconnect the harness connector at the G10 Cooling Fan Motor.
2. Verify a test lamp illuminates between the ground circuit and B+.
   • If the test lamp does not illuminate 
   1. Ignition OFF, remove the test lamp.
   2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
   • Go to next step: If the test lamp illuminates 
3. Test or replace the G10 Cooling Fan Motor. Replace the cooling fan fuses if necessary.

Low or High Speed Inoperative

1. Disconnect the following cooling fan relays, ignition ON:
   • KR20C Cooling Fan Low Speed Relay
   • KR20P Cooling Fan Medium Speed Relay
   • KR20D Cooling Fan High Speed Relay
2. Verify a test lamp illuminates between ground and each of the cooling fan relay B+ circuit terminals listed below:
   • KR20C Cooling Fan Low Speed Relay terminal 30
   • KR20P Cooling Fan Medium Speed Relay terminal 30
   • KR20D Cooling Fan High Speed Relay terminal 30
   • If the test lamp does not illuminate and the circuit fuse is good 
   1. Ignition OFF, remove the test lamp.
   2. Test for less than 2 Ω in the appropriate relay B+ circuit, end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
   • Go to next step: If the test lamp does not illuminate and the circuit fuse is open 
   1. Ignition OFF, disconnect the harness connector at the G10 Cooling Fan Motor.
   2. Test for infinite resistance between the appropriate relay controlled output circuit terminal listed below and ground:
   • KR20C Cooling Fan Low Speed Relay terminal 87
   • KR20P Cooling Fan Medium Speed Relay terminal 87
   • KR20D Cooling Fan High Speed Relay terminal 87
     • If less than infinite resistance, repair the short to ground in the circuit.
     • If infinite resistance, test or replace the G10 Cooling Fan Motor, replace the fuse as necessary.
   • Go to next step: If the test lamp illuminates 
3. Ignition OFF, install all of the previously removed KR20 Cooling Fan Relays. Disconnect the harness connector at the G10 Cooling Fan Motor, ignition ON.
4. Command the cooling fan ON at high or low speed as appropriate with a scan tool.
5. Verify a test lamp illuminates between ground and the G10 Cooling Fan Motor B+ circuit terminal.
   • If the test lamp does not illuminate at each terminal 
   1. Ignition OFF, remove the test lamp.
   2. Disconnect the appropriate relay from the list below:
      • KR20C Cooling Fan Low Speed Relay
      • KR20P Cooling Fan Medium Speed Relay
      • KR20D Cooling Fan High Speed Relay
   3. Test for less than 2 Ω in the relay controlled output circuit, end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, test or replace the relay.
   • Go to next step: If the test lamp illuminate at each terminal 
6. Test or replace the G10 Cooling Fan Motor.