Cabin Heater - PTC

This procedure guides the removal and replacement of the PTC (Positive Temperature Coefficient) cabin heater assembly on the 2023 Chevrolet Bolt EUV electric vehicle.

Warnings

Tools required

Parts

• PTC cabin heater assembly × 1 — Use OEM specification
• Coolant line O-rings × 2 — Use OEM specification
• High voltage connector seal × 1 — Use OEM specification

Fluids

• ACDelco DEX-COOL (Orange) — 2 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Turn off vehicle and remove key fob from cabin
3. Open hood and disconnect 12V auxiliary battery negative terminal
4. Wait minimum 5 minutes for high voltage capacitors to discharge
5. Remove engine cover by lifting from rear and pulling forward
6. Place coolant drain pan beneath vehicle under HVAC area
7. Remove lower dash panel on passenger side to access heater assembly from cabin
8. Photograph all electrical connections before disconnection for reference

Procedure

1. 1

   Verify high voltage system de-energization
   Using a CAT III rated multimeter, test between high voltage bus bars at the main battery disconnect to verify 0V DC. Do not proceed if any voltage is detected. Verify high voltage interlock loop is open by checking indicator on instrument cluster.
2. 2

   Drain coolant from PTC heater circuit
   Locate coolant drain valve on the low-temperature coolant circuit near the PTC heater. Attach drain hose to valve and route to drain pan. Open valve and allow approximately 1-2 quarts to drain. Close valve when flow stops.
3. 3

   Disconnect coolant lines from PTC heater
   Using appropriate wrench, loosen coolant line fittings at inlet and outlet ports on PTC heater assembly. Be prepared for residual coolant spillage. Remove fittings completely and cap open lines to prevent contamination. Remove and discard O-rings from fittings.
   Torque spec

   Coolant Line Fittings15 Nm (11 lb-ft)
4. 4

   Remove high voltage connector cover
   Locate orange high voltage connector on side of PTC heater assembly. Remove cover screws securing the protective cover over the HV connector. Carefully lift cover away and set aside.
   Torque spec

   Cover Screws11 Nm (8 lb-ft)
5. 5

   Disconnect high voltage connector
   While wearing high voltage safety gloves, press release tab on orange HV connector and carefully pull connector straight out from PTC heater assembly. Do not twist or bend connector. Inspect connector seal for damage and replace if necessary. Position connector away from work area.
6. 6

   Disconnect low voltage control connector
   Locate the low voltage control connector (typically gray or black) on the PTC heater assembly. Press connector release tab and disconnect. Remove connector bolt if equipped.
   Torque spec

   Connector Bolts7 Nm (5 lb-ft)
7. 7

   Remove temperature sensor
   Disconnect coolant temperature sensor electrical connector from sensor mounted on PTC heater housing. Remove sensor mounting bolt and carefully extract sensor from housing. Inspect sensor O-ring.
   Torque spec

   Sensor Bolts11 Nm (8 lb-ft)
8. 8

   Remove PTC heater mounting bracket
   Locate and remove bracket bolts securing the support bracket to the PTC heater assembly and vehicle structure. There are typically 2-3 bracket bolts. Support heater assembly weight while removing final bolts.
   Torque spec

   Bracket Bolts20 Nm (15 lb-ft)
9. 9

   Remove PTC heater mounting bolts
   Remove the main mounting bolts securing PTC heater assembly to HVAC housing or vehicle structure. There are typically 4 mounting bolts. Carefully support assembly weight to prevent dropping.
   Torque spec

   Mounting Bolts27 Nm (20 lb-ft)
10. 10

    Extract PTC heater assembly
    Carefully maneuver PTC heater assembly out of mounting position, being mindful of remaining coolant spillage. Tilt assembly as needed to clear surrounding components. Remove assembly from vehicle and place on clean work surface.
11. 11

    Install new PTC heater assembly
    Position new PTC heater assembly into mounting location, aligning mounting bolt holes. Install mounting bolts hand-tight first to verify proper alignment, then torque to specification in a cross-pattern.
    Torque spec

    Mounting Bolts27 Nm (20 lb-ft)
12. 12

    Install mounting bracket
    Position support bracket and install bracket bolts. Torque bracket bolts to specification.
    Torque spec

    Bracket Bolts20 Nm (15 lb-ft)
13. 13

    Install temperature sensor
    Install temperature sensor with new O-ring into PTC heater housing. Torque sensor bolt to specification. Connect sensor electrical connector.
    Torque spec

    Sensor Bolts11 Nm (8 lb-ft)
14. 14

    Reconnect electrical connectors
    Reconnect low voltage control connector to PTC heater assembly. Ensure connector locks fully. If equipped with connector bolt, torque to specification. Reconnect high voltage connector ensuring it seats fully and locks. Install HV connector cover and torque cover screws.
    Torque spec

    Connector Bolts7 Nm (5 lb-ft)

    Cover Screws11 Nm (8 lb-ft)
15. 15

    Reconnect coolant lines
    Install new O-rings on coolant line fittings, lubricating lightly with coolant. Connect coolant lines to inlet and outlet ports on PTC heater assembly. Torque coolant line fittings to specification.
    Torque spec

    Coolant Line Fittings15 Nm (11 lb-ft)
16. 16

    Refill and bleed cooling system
    Using coolant refill funnel, add ACDelco DEX-COOL coolant to low-temperature cooling system reservoir to proper level. Start vehicle and allow to run with climate control set to maximum heat to circulate coolant and purge air. Monitor coolant level and add as necessary. Check for leaks at all connection points.

Reassembly

1. Reinstall lower dash panel in cabin
2. Reinstall engine cover
3. Reconnect 12V auxiliary battery negative terminal
4. Clear any diagnostic trouble codes using scan tool

Verification

• Start vehicle and verify no warning lights related to high voltage or HVAC systems
• Set climate control to maximum heat and verify warm air output from cabin vents within 2-3 minutes
• Monitor coolant level after test drive and top off if necessary
• Verify no coolant leaks at PTC heater connections after system reaches operating temperature
• Use scan tool to verify PTC heater is receiving command signals and reporting normal operation
• Check for stored diagnostic trouble codes and verify none related to PTC heater system

Related trouble codes on this vehicle

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