851519 Removing and Installing Heater/Air-Conditioning Unit

WM 851519 Removing and installing heater/air-conditioning unit

Technical values





Preliminary work

1. Drain engine coolant. -> 193817 Draining and topping up with coolant (includes bleeding) - section on "draining" Service and Repair
2. Remove the carrier for the instrument panel. -> 701219 Removing and installing carrier for instrument panel - section on "Removing" 701219 Removing and installing bracket for dashboard
3. Remove the condenser-evaporator line and compressor-evaporator line at the expansion valve and close the connections. -> 877019 Removing and installing expansion valve - section on "Removing" 877019 Removing and installing expansion valve

Removing heater/air-conditioning unit

CAUTION

Risk of material damage

-> Remove ignition key. Disconnect battery. Route or isolate the ground strap so that all contact with a ground carrier (e.g. body, seat frame) is avoided. -> 90 Work instructions after disconnecting the battery





Overview of heater/air-conditioning unit

1. Support the heater/air-conditioning unit under the centre section -A- and under the evaporator -B- with a plastic or wooden board.





Supporting heater/air-conditioning unit

2. Unclip wiring harness on the left heat exchanger cover.





Unclipping wiring harness on the left heat exchanger cover

3. Unscrew both fastening screws on the left heat exchanger cover and unclip the cover.
4. Unscrew the fastening screw of the right heat exchanger cover and unclip the cover.





Unscrewing fastening screw of the right heat exchanger cover

5. Pull the retaining clips -arrows A- off the coolant supply line and return line.





Pulling off retaining clips on coolant lines

Information

- Line the driver's footwell with very absorbent material.

6. Pull the interior carpet away from the coolant lines and place a suitable collecting container in position.





Pulling interior carpet away from the coolant lines

7. -arrows B- Slowly pull out the lines from the heat exchanger and drain the coolant into the collecting container.
8. Unscrew both centre air guide fastening screws -4- for the back seat area and pull out the upper air guide toward the rear -arrow A- and the lower one toward the front -arrow B-.





Releasing and removing centre air guide

9. Pull out centre air vents on the left -A- and right -B-.





Removing left and right air vents

10. Turn the left and right temperature sensor -90°- and pull out of the heater/air-conditioning unit.





Releasing and removing temperature sensor

11. Pull the centre air vents for the footwell downwards from the heater/air-conditioning unit, lift it toward the rear, and pull it out of the air vents for the footwell.
12. Release the electric central connector -A- ( -arrows a- ), lever apart the connector lock -B- with two screwdrivers and pull off.





Pulling off electric central connector

Information

- Make sure not to damage the insulation of the main wiring harness.

13. The main wiring harness is secured to the heater/air-conditioning unit with tie-wraps. Separate the tie wraps carefully with side cutters.





Cutting through main wiring harness tie-wraps on the heater/air-conditioning unit

14. The main wiring harness runs along the right A-pillar and is secured to the heater/air-conditioning unit in the fan area with a tie-wrap. Separate the tie wrap carefully with side cutters.





Cutting through tie-wrap in fan area

15. Disconnect the water drainage hose from the air-conditioning unit.





Disconnecting water drainage hose from air-conditioning unit

16. Detach the main wiring harness on the heater/air-conditioning unit.





Detaching main wiring harness on heater/air-conditioning unit

17. Grasp the heater/air-conditioning unit on the left and right, pull backwards about 5 cm and remove completely.

Installing heater/air-conditioning unit

Information

Before the heater/air-conditioning unit is installed again, the following points must be checked:

- Check the water drainage hose for any cracks, deformities and other damage.





Water drainage hose

- Check on the body for damage to both mounts (stars) for the heater/air-conditioning unit. The stars must be able to turn for installation.





Checking the mounts (stars) for the heater/air-conditioning unit

- Both mounts for the stars on the heater/air-conditioning unit must not be damaged.





Checking the mounts for the stars on the heater/air-conditioning unit

1. Position the plastic or wooden boards used for removal in the vehicle. Position the heater/air-conditioning unit in the vehicle. Get a second person to check the position of the stars - twist them if necessary.

WARNING

Risk of damage to the mounts (stars).

-> The heater/air-conditioning unit must be supported

2. Slide the heater/air-conditioning unit onto both mounts (stars) and support it.
3. Push the water drainage hose onto the air-conditioning unit and make sure it is seated correctly.





Pushing the water drainage hose onto the air-conditioning unit

4. Engage the main wiring harness on the heater/air-conditioning unit.





Engaging main wiring harness on heater/air-conditioning unit

5. Lay the main wiring harness on the heater/air-conditioning unit and position it on the heater/air-conditioning unit -A- and -B- using one tie-wrap each.





Laying and positioning main wiring harness on heater/air-conditioning unit

6. Insert the electric central connectors -A- and -B- into the plug connections until they click into place.





Inserting central connectors

7. Plug the centre temperature sensor on the left and right into the heater/air-conditioning unit and turn -90°-.





Installing temperature sensor

8. Insert the centre air vents for the footwell into the air guides for the footwell and push onto the heater/air-conditioning unit.
9. Connect the centre air vents on the left -A- and right -B-.





Connecting centre air vents on the left and right

10. Slide the lower centre air guide into the rear air guide -arrow B- , press the upper centre air guide onto the heater/air-conditioning unit -arrow A- , and screw down with the two fastening screws -4-. => Tightening torque: 1 ftlb.





Sliding lower centre air guide into rear air guide and securing

11. Position the carrier for the instrument panel. -> 701219 Removing and installing the carrier for the instrument panel - section on "Installing" 701219 Removing and installing bracket for dashboard
12. Tighten the fastening screws -1- and -2-. => Tightening torque: 7.5 ftlb.
13. Remove the support for the heater/air-conditioning unit.

Information

- Always replace O-rings.

14. Insert the coolant supply line and return line -B- into the heat exchanger.





Inserting coolant lines into the heat exchanger

15. Push on the retaining clips -A- until the clips click into place.
16. Top up engine coolant. -> 193817 Draining and topping up with coolant (includes bleeding) - section on "Topping up" Service and Repair.
17. Check the heating system for leaks.
18. Clip in left cover and secure with the fastening screws. => Tightening torque: 1 ftlb.





Securing left cover

19. Clip in wiring harness on the left heat exchanger cover.
20. Install the condenser-evaporator line and the compressor-evaporator line on the expansion valve. -> 877019 Removing and installing expansion valve - section on "Installing" 877019 Removing and installing expansion valve

Subsequent work

1. Install the carrier for the instrument panel. -> 701219 Removing and installing the carrier for the instrument panel - section on "Installing" 701219 Removing and installing bracket for dashboard
2. Carry out work instruction after disconnecting the battery. -> 90 Work instructions after disconnecting the battery.