EV Chiller Unit

This procedure covers the removal and replacement of the EV chiller unit on the 2023 Chevrolet Bolt EUV, which is part of the battery thermal management system.

Warnings

Tools required

Parts

• EV chiller unit assembly × 1 — Use OEM specification
• Chiller coolant line O-rings × 4 — Use OEM specification
• Refrigerant line seal washers × 2 — Use OEM specification
• Hose clamps × 4 — Use OEM specification

Fluids

• ACDelco DEX-COOL (Orange) — 3 qt
• R-1234yf refrigerant

Preparation

1. Park vehicle on level surface and apply parking brake
2. Ensure high voltage battery has been off for at least 15 minutes to allow capacitors to discharge
3. Open hood and locate 12V battery in front compartment
4. Disconnect 12V negative battery terminal and wait 2 minutes for system shutdown
5. Remove high voltage service disconnect (orange plug) located in rear cargo area under cover
6. Verify high voltage disconnect with multimeter at service points if equipped
7. Remove front underbody shield to access chiller unit from below
8. Place coolant drain pan under vehicle beneath chiller unit location

Procedure

1. 1

   Recover refrigerant from AC system
   Connect AC recovery machine to service ports. Follow machine instructions to fully recover R-1234yf refrigerant from the system. Record the amount recovered for proper recharging. Ensure recovery is complete before proceeding with any line disconnection.
2. 2

   Drain low-temperature coolant loop
   Locate the drain valve on the low-temperature coolant reservoir. Attach drain hose and route to collection pan. Open drain valve and allow coolant to drain completely. The chiller unit is part of the low-temp loop, not the main engine cooling loop. Expect approximately 2-3 quarts to drain.
3. 3

   Disconnect electrical connectors
   Locate the chiller unit mounted in front lower section behind bumper. Disconnect the chiller pump electrical connector by pressing release tab. Disconnect the temperature sensor connector from the chiller body. Label connections if needed for reassembly reference.
4. 4

   Remove refrigerant line connections
   Using appropriate wrench, carefully loosen and remove the refrigerant line fittings from the chiller unit. There are two connections: inlet and outlet. Cap all open refrigerant ports immediately to prevent moisture contamination. Discard old seal washers.
5. 5

   Disconnect coolant lines
   Using hose clamp pliers, release the hose clamps on all four coolant connections (two inlet, two outlet). Carefully remove coolant hoses from chiller unit ports. Have absorbent material ready to catch residual coolant. Cap or plug open coolant ports to prevent contamination.
   Torque spec

   Hose Clamps3 Nm (2 lb-ft)
6. 6

   Remove mounting bracket cover
   Locate the protective cover over the chiller mounting bracket. Remove the cover screws securing the cover panel. Set cover aside carefully to avoid damage to clips or mounting points.
   Torque spec

   Cover Screws11 Nm (8 lb-ft)
7. 7

   Remove chiller mounting fasteners
   Remove the mounting bolts securing the chiller unit to the vehicle frame. There are typically three mounting bolts. Support the chiller unit weight while removing the final bolt to prevent it from dropping.
   Torque spec

   Mounting Bolts27 Nm (20 lb-ft)
8. 8

   Remove chiller unit from vehicle
   Carefully lower the chiller unit assembly from its mounting position. Maneuver the unit through the lower access area, being careful not to damage surrounding components or wiring. Inspect mounting area for any debris or damage before installing new unit.
9. 9

   Install new chiller unit
   Position the new chiller unit into the mounting location. Align mounting holes with frame brackets. Ensure all clearances are adequate and no wires or hoses are pinched. Hand-thread all mounting bolts before torquing.
10. 10

    Secure chiller mounting bolts
    Using a calibrated torque wrench, tighten all mounting bolts to specification in a crossing pattern to ensure even seating. Verify unit is secure and properly aligned.
    Torque spec

    Mounting Bolts27 Nm (20 lb-ft)
11. 11

    Reinstall mounting bracket cover
    Position the protective cover over the mounting bracket. Install and torque cover screws to specification. Ensure cover is seated properly and not interfering with any moving parts or lines.
    Torque spec

    Cover Screws11 Nm (8 lb-ft)
12. 12

    Connect coolant lines
    Install new coolant line O-rings on chiller ports, lubricating lightly with fresh coolant. Slide coolant hoses onto ports, ensuring they are fully seated. Install new hose clamps and torque to specification. Ensure clamps are positioned correctly away from potential wear points.
    Torque spec

    Hose Clamps3 Nm (2 lb-ft)
13. 13

    Reconnect refrigerant lines
    Install new seal washers on refrigerant line fittings. Connect refrigerant lines to chiller unit inlet and outlet ports. Hand-tighten fittings first, then torque to specification using a backup wrench to prevent component damage. Do not over-torque as this can damage the aluminum ports.
    Torque spec

    Coolant Line Fittings15 Nm (11 lb-ft)
14. 14

    Reconnect electrical connections
    Connect the temperature sensor connector to the chiller unit, ensuring it clicks into place. Connect the chiller pump electrical connector, verifying proper seating. Ensure no wires are pinched or stretched.
15. 15

    Refill coolant and evacuate AC system
    Refill the low-temperature coolant loop with fresh ACDelco DEX-COOL through the reservoir to the proper level. Use AC service machine to evacuate the refrigerant system for at least 30 minutes to remove moisture. Recharge with the recorded amount of R-1234yf refrigerant plus any additional amount needed per specifications.

Reassembly

1. Reinstall front underbody shield and secure all fasteners
2. Reinstall high voltage service disconnect (orange plug) and secure cover
3. Reconnect 12V negative battery terminal
4. Start vehicle and allow thermal management system to initialize
5. Check for coolant leaks at all connection points while system circulates
6. Verify coolant level in low-temperature reservoir after system reaches operating temperature

Verification

• Use refrigerant leak detector to check all AC line connections for leaks
• Monitor coolant level for 24 hours and top off if necessary
• Verify chiller pump operation by listening for pump noise when thermal management activates
• Check for proper temperature readings using vehicle diagnostics if available
• Confirm no warning lights or fault codes related to thermal management system
• Test drive vehicle and verify battery thermal management functions normally during charging and driving

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