MOUNT 1868403 - Caterpillar

Illustration 1 g06246603
(1) Blower motor
(2) Blower motor controller
Diagnostics
Illustration 2 g06246611
Partial electrical schematic
Use the fan switch to set the air flow to the maximum High position.
Remove connector (H) from the blower motor connector. Check to see if voltage is applied between the "WH/GRN" wire and the "BK/BLU" wire on connector (H). If there is no voltage, see Step 3. If there is voltage, then the blower motor has failed. Replace the blower motor.
Check the battery voltage applied between the "WH/GRN" wire at (+) side of the blower motor and ground. If there is no voltage, see Step 4. If there is voltage, see Step 7.
Check the blower motor relay. Directly connect the "WH/GRN" wire and the "RD" wire on the blower motor relay to see if the motor rotates. If the blower motor does not rotate, the wire harness is defective. Check and repair the wire harness or replace the wire harness. If the blower motor rotates, see Step 5.
Check to see if battery voltage is applied between the "RD" wire of the blower motor relay and ground. If there is no battery voltage, check and repair the wire harness or replace the wire harness. If there is voltage, see Step 6.
Ground the "BK/BLU" wire of the blower motor to see if the blower motor rotates. If the blower motor does not rotate, replace the blower motor relay. If the blower motor rotates, check and repair the wire harness or replace the control panel.
Check to see if there is voltage between the "BLU/BK" wire and the "BK" wire on the fan control. Check to see if there is voltage between the "BR/BK" wire and the "BK" wire on the fan control. If there is no voltage, replace the control panel. If there is voltage, see Step 8.
Remove and check the fan control. Refer to "Specifications". If the fan control checks out normal, check and repair the harness. If the fan control is faulty, replace the fan control.Specifications
Illustration 3 g06244200
Fan Control
Table 1
Fan Control
Terminal Number Conductivity
1 2 3 4
Tester + − Exists (4.7k Ohm)
− + Does not exist
+ − Exists (Diode parallel forward direction) Blower motor voltage (reference value) for each preset air amount at ACC voltage 27 V.Lo ... 10 VMi ... 13.3 VM2 ... 16 VM3 ... 19.9 VM4 ... 23.2 VHi ... 27 V