An Updated Blower Assembly is Available for Certain Off-Highway Trucks {7320} Caterpillar

Off-Highway Truck/Tractor

769C (S/N: 01X75400-UP)

769D (S/N: 5SS76001-UP)

772 (S/N: RLB865-UP)

773B (S/N: 63W76006-UP)

773D (S/N: NBJ76001-UP; 7ER76001-UP; 7CS75003-UP)

773E (S/N: BDA78001-UP; PRB1-UP; KEG235-UP; ASK967-UP; DJS1-UP)

777C (S/N: 4XJ78005-UP)

777D (S/N: AGC75005-UP; FKR2114-UP; 3PR77001-UP)

777E (S/N: KDP1-UP)

OEM POWERTRAIN (S/N: DTE561-UP)

Quarry Truck

771C (S/N: 3BJ76001-UP)

771D (S/N: BCA76002-UP; 6YS76004-UP)

775D (S/N: 8AS75004-UP)

775E (S/N: BEC75001-UP)

A 550-2449 Cab Blower (Kit) is available for certain Off-Highway Trucks. Installation of the cab blower kit will extend the service life of the climate control system.

The current 174-1489 Electric Motor Gp is being replaced by the 453-2441 Blower As. Refer to the parts table and following procedure for rework information.

The following changes are now available for the products within the listed serial numbers.

Note: The 550-2449 Cab Blower (Kit) is not serviceable. All required parts must be ordered individually.

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Do not operate or work on this product unless you have read and understood the instruction and warnings in the relevant Operation and Maintenance Manuals and relevant service literature. Failure to follow the instructions or heed the warnings could result in injury or death. Proper care is your responsibility.

Rework Procedure

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Illustration 1	g06266772
Front view of the cab

1. Remove front cab panel to gain access to the blower assembly. Retain the panel and fasteners to reinstall later.
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   Illustration 2	g06270168
   View of HVAC enclosure (A) Old blower behind plate

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   Illustration 3	g06270171
   View of outside of HVAC enclosure (B) Main harness receptacles (C) Existing grommet (D) Wire clips (E) Fasteners (F) Support handles (G) Outer plate

2. Disconnect three wiring receptacles (B) from the main harness assembly.

   Remove existing grommet (C), along with two wire clips (D) and retain for later use.

   Feed the wiring harness assembly through the hole in the cover plate to the Blower compartment.

   Remove all the fasteners (E) and release three support handles (F) connecting the HVAC unit to the frame.

   Remove outer plate (G).

   Note: The blower assembly and resistor components are attached to the outer plate and will come out with plate (G) when plate (G) is removed.

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   Illustration 4	g06270409
   View of blower unit removed from HVAC housing

3. Disconnect the harness from blower, remove any wire ties securing the harness and resistor harnesses to the plate. Remove the harness and retain for later.

   Note: Note which wires go on which tab on the resistor before removing this portion of the harness connection.

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   Illustration 5	g06270443
   View of the back of the blower box (D1) 3.9 mm (0.15354 inch) (D2) 0.08 mm (0.003 inch) (D3) 217.5 mm (8.6 inch) (D4) 111.0 mm (4.4 inch) (D5) 10.8 mm (0.4 inch) (D6) 13 mm (0.51 inch)

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   NOTICE
   Ensure that all metal shavings are removed from the HVAC unit after drilling is complete (may need to remove the second cover plate to accomplish removing all the shavings).

4. Drill four 13 mm (0.51 inch) clearance holes (D6) in the back plate of the HVAC assembly for the adapter plate weld nuts.
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   Illustration 6	g06270710
   View of new blower sub assembly (1) 153-6932 Gasket (2) 453-2441 Blower As (3) 550-2450 Plate As (6) 8T-0337 Screw

5. Assemble blower assembly (2) and gasket (1) onto plate assembly (3) using four screws (6).
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   Illustration 7	g06270783
   View of new blower assembly mounted onto back inner plate of the HVAC unit

6. Use the existing hardware to secure the blower/ plate subassembly into the back inner plate of the HVAC unit.

Reconnecting the Harnesses

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Illustration 8	g06270789

1. Swap the two wires (power and ground) in the blower harness so that the wires match the new blower motor (2).

   Note: The new blower motor is wired opposite the old blower.

2. Connect blower resistor harness to new blower resistor. Secure the connection with one cable strap.
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   Illustration 9	g06267013
   View of resistor pack (A) New resistor pack (B) Old resistor pack

3. Connect the resistor harness to the resistor pack.

   Note: Leave the Low/Min Terminal empty on the new blower resistor.

Completing the Rework

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Illustration 10	g06270850
View of front of the HVAC unit (A) Grommet (B) P Clip

1. Thread the remaining harness back out through the cut out in the face of 550-2451 Plate As (4). Reuse grommet (A) to secure the harness in the cut out in plate assembly (4).

2. Install new 550-2451 Plate As (4) onto the HVAC unit using the existing hardware retained earlier.

3. Reinstall "P" clips (B) removed prior to secure the existing harness.
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   Illustration 11	g06271110
   View of the front of the cab

4. Reconnect the blower harnesses to the cab harness connections.

5. Reinstall the front cab panel.