TRANSFORMER 2157471 - Caterpillar

Illustration 3 g00482642
Heater unit
Check the relay for HI fan speed.Expected Result: Relay (19) is bad.Results:
OK - Replace the relay.
NOT OK - Replace blower motor (11). The fan wheel is part of the blower motor.Problem: The blower motor rotates at high speed only.
Check all fan speeds. If the blower only rotates when the HI fan speed is chosen, the BLC (blower linear control) is bad.Expected Result: The (BLC) is bad.Results:
OK - Replace the (BLC) (18) .
NOT OK - Refer to "Problem: The blower motor is nonfunctional and no error code exists."if the blower does not rotate at any speed.Problem: The blower motor is nonfunctional and no error code exists.
Check the main fuse (20 Amp).Reference: Refer to Testing and Adjusting, "Heating System Schematic" for the proper wiring diagram.Expected result: The fuse is good.Results:
OK - Proceed to step 2.
NOT OK - Check the circuit and replace the fuse as required.
Check relay (19) .Expected Result: The relay is functioning properly.Results:
OK - Proceed to step 3.
NOT OK - Replace relay (19) .
Unplug the blower motor. Increase the fan speed until the highest fan speed is attained. Check that voltage (24V) is present at wire 2-PK/BU at the blower motor.Expected result: Voltage is present.Results:
OK - Proceed to step 4.
NOT OK - Replace the (BLC) (18) .
Check that ground is present at wire 2-GN/RD at the blower motor.Expected Result: Ground is present.Results:
OK - Proceed to step 5.
NOT OK - If ground is not present, proceed to step 6.
Apply voltage (24V) to the blower motor.Expected Result: The motor turns without excessive noise, vibration or blower wheel rubbing.Results:
OK - Replace the (BLC) (18) .
NOT OK - If the motor does not turn properly, repair the obstruction or replace the blower motor.
Check the signal output of the control panel.Expected Result: The control panel is correct.Results:
OK - A wiring problem exists. Check the wiring harness and the connectors. Repair any problems that are found.
NOT OK - Replace the control panel.Problem: No heat is provided, but the blower motor is functional.
Check the water temperature.Expected Result: The water temperature is normal.Results:
OK - Proceed to step 3.
NOT OK - Proceed to step 2.
Check if the water supply valve on the engine block is open.Expected Result: The valve is open.Results:
OK - Proceed to step 3.
NOT OK - Open the valve.
Check the engine coolant level.Expected Result: The coolant level is correct.Results:
OK - Proceed to step 4.
NOT OK - Refill the coolant to the correct level. Be sure to purge air from the coolant system.
Check for a coolant line that is clogged and check for a coolant line that is bent.Expected Result: All coolant lines are clean and free of obstructions.Results:
OK - Proceed to step 5.
NOT OK - Remove any foreign material and repair any bent lines.
Check the heater core for leaks.Expected Result: The heater core is not leaking.Results:
OK - Proceed to step 6.
NOT OK - Replace the heater core.
Observe the LED for adjusting temperature.Expected Result: The LED is functioning properly.Results:
OK - Engage the link arm between the damper motor and the damper door. This link