Circuit/System Testing

Ignition OFF, disconnect the cooling fan relays.
Connect a 30A fused jumper between the relay switch B+ circuit and the ground circuit at the series/parallel fan 2 relay connector. This will complete the left side or main fan ground circuit. Leave this jumper in place for the remainder of this procedure.
NOTE: The following test must be performed on both the fan 3 relay circuit and the fan 1 relay circuit.
Ignition ON, verify that a test lamp illuminates between the relay switch B+ circuit and ground.
- If the test lamp does not illuminate, test the relay switch B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay switch B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the relay.
  NOTE: The following test must be performed first on the fan 3 relay circuit and next on the fan 1 relay circuit. Leave the jumper connected to the fan 1 relay circuit for the next test.
Connect a 30A fused jumper between the relay switch B+ circuit and the relay controlled output circuit. Verify the appropriate fan is activated
- If the appropriate fan does not activate, test the relay controlled output circuit for a short to ground or an open/high resistance. If the circuit tests normal, test the fan ground circuit for an open/high resistance. If the circuit tests normal, replace the fan.
Install the fan 2 relay. Verify both fans activate at low speed.
- If both fans do not activate, test the relay controlled output circuit of the fan 2 relay for a short to ground or an open/high resistance.
If all circuits test normal, test or replace the relay.