schematics and diagrams: How to replace heater core on Audi ?

Removal & Installation

Disconnect the negative battery cable.

Drain the engine coolant.

Completely remove the instrument panel.

From the engine compartment, label and remove all hoses and necessary wiring.

Remove and plug all A/C lines.

Remove and plug the coolant lines for the heater core.

On Passat models using a heater core that is not completely surrounded by the air box housing, remove the self tapping screws if installed, then slide the heater core out of the housing.

On A4 and Passat models with the heater core installed into the housing:

Remove the heater box housing which contains the evaporator.

Unclip the heater core box.

Remove the heater core.

Installation is the reverse of removal. Always make sure all seals are installed properly during the installation process.

On Passat models using a heater core that is not completely surrounded by the air box housing, install the heater core with a self adhesive seal installed along the top of the fins on the side of the heater core that is near the inlet and outlet spigots and around the end of the heater core spigot housing to seal the heater core in the housing. If the heater core fit is slightly loose, secure it to the housing with self-tapping screws.

If disassembled, seal all seams of the heater box with RTV.

The balance of the installation is in reverse order of removal making sure to have a MVAC certified technician evacuate and recharge the A/C system.

NOTE

Consult the under hood label for the correct refrigerant type and amount installed in the system. The R134A type of refrigerant was introduced as standard equipment in the 1993 models.

A4 And TT

Perform the Output Diagnostic Test Mode (DTM) using the VAG 1551 function 03 by performing the following procedure:
NOTE
If equipped with power seats, move the seats as far rearward as possible. Also, obtain the anti-theft radio coding and the preset radio stations from the owner.

Once the air flow flap closes, cancel the Output DTM by pressing the -C- button.

Discharge and recover the air conditioning system refrigerant.

Remove or disconnect the following:

Air plenum cover, the water guide and the dust/pollen filter, located at the right side
Negative battery cable
Positive battery cable and remove the battery
Coolant recovery tank cap to relieve the pressure from the system

Drain the cooling system into a clean container for reuse.

Label and disconnect or clamp off the heater hoses from (at) the heater core.

Place a container under the right heater core tube, induce pressurized air to the left tube and blow compressed into the tube to drain excess coolant.

Remove or disconnect the following:

Air conditioning system vacuum supply hose and attach it at the heater core inlet/outlet
Heater core-to-chassis boot
Refrigerant lines-to-evaporator core clamp bolt, disconnect the refrigerant line clamp and discard the O-rings. Plug the openings to prevent contamination.
Evaporator core-to-chassis boot
Low pressure switch electrical connector and secure it to the evaporator fixture

Remove the glove box, the driver-s side lower shelf and the instruments panel center section by removing or disconnecting the following:

5 glove box-to-instrument panel bolts and the glove box
3 clips, remove the 3 stowage compartment bolts and the stowage compartment at the driver-s side
Rear console
3 the knobs, remove the 4 center instrument panel trim bolts, the 2 screws and the trim
Radio
4 front console-to-instrument panel bolts
Trim cover and the console-to-chassis nut at the left side of the front console
Pedal assembly at the driver-s side

Place the front wheels in the straight-ahead position.

Remove the driver-s side air bag module by removing or disconnecting the following:

Air bag module-to-steering wheel screws using a T30 Torx bit; the screws are located on both sides of the steering wheel
Air bag module and disconnect the electrical connector
Place the air bag module in a safe place with the front facing upward.

Remove the steering wheel by removing or disconnecting the following:

Steering wheel nut
Horn and air bag electrical connectors
4 carrier unit-to-steering wheel bolts and the carrier unit
Steering wheel

At the steering column-to-instrument panel connection, secure the steering column wire to keep the steering column from sliding apart.

Remove or disconnect the following:

Steering column-to-steering gear bolt
Electronic box electrical connectors located in the left air plenum chamber
All instrument panel-to-chassis electrical connectors

Remove the instrument panel by removing or disconnecting the following:

Instrument panel-to-chassis bolts
Any necessary electrical connectors
Instrument panel

Remove or disconnect the following:

Ducts, heater/air conditioning housing assembly-to-chassis bolts and the assembly
Heater core-to-heater/air conditioning housing screws
Press the heater core-to-heater housing catches and remove the heater core from the heater/air conditioning housing

Fig. Exploded view of the air bag module, steering wheel and related components-A4

Fig. Exploded view of the rear console assembly-A4

Fig. Exploded view of the front console assembly-A4

Fig. Exploded view of the instrument panel assembly-A4

Fig. Exploded view of the heater core, heater/air conditioning housing and related components-A4

Fig. Removing the heater core-A4

To install:

Install or connect the following:

Heater core to the heater/air conditioning housing and press the heater core into heater housing until the latches catch
Heater core-to-heater/air conditioning housing screws
Heater/air conditioning housing assembly and connect the ducts

Install the instrument panel by installing or connecting the following:

Instrument panel
Any necessary electrical connectors
Instrument panel-to-chassis bolts and torque the bolts to 44 inch lbs. (5 Nm)
All instrument panel-to-chassis electrical connectors
Electronic box electrical connectors located in the left air plenum chamber
Steering column-to-steering gear bolt

Install the steering wheel by installing or connecting the following:

Steering wheel
Carrier unit and the 4 carrier unit-to-steering wheel bolts
Horn and air bag electrical connectors
Steering wheel nut

Install the driver-s side air bag module by installing or connecting the following:

Air bag module and connect the electrical connector
Torque the air bag module-to-steering wheel screws to 53 inch lbs. (6 Nm) using a T30 Torx bit; the screws are located on both sides of the steering wheel
Pedal assembly at the driver-s side

Install the glove box, the driver-s side lower shelf and the instruments panel center section by installing or connecting the following:

Console-to-chassis nut and the trim cover at the left side of the front console. Torque the nut to 31 inch lbs. (3.5 Nm)
4 front console-to-instrument panel bolts and torque the bolts to 44 inch lbs. (5 Nm)
Radio
4 center instrument panel trim, the 4 center instrument panel trim bolts, the 2 screws and the 3 the knobs. Torque the bolts to 44 inch lbs. (5 Nm) and the screws to 31 inch lbs. (3.5 Nm)
Rear console
Stowage compartment, the 3 stowage compartment bolts and engage the 3 clips. Torque the bolts to 44 inch lbs. (5 Nm)
Glove box and the 5 glove box-to-instrument panel bolts; then, torque the bolts to 44 inch lbs. (5 Nm)

Install or connect the following:

Low pressure switch electrical connector
Evaporator core-to-chassis boot.
Refrigerant lines-to-evaporator core clamp and connect the refrigerant line clamp bolt making sure to use new O-rings
Heater core-to-chassis boot
Air conditioning system vacuum supply hose
Heater hoses to the heater core

Refill the cooling system.

Install the coolant recovery tank cap.

Install the battery and connect the positive (+) battery cable.

Connect the negative (() battery cable.

At the right side, install the dust/pollen filter, the water guide and the air plenum cover.

Evacuate, charge and leak test the air conditioning system.

Operate the engine to normal operating temperature; then, check the climate control operation and check for leaks.

A6

NOTE

If equipped with power seats, move the seats as far rearward as possible. Also, acquire the anti-theft radio coding from the owner.

Remove or disconnect the following:
NOTE
If desired, instead of draining cooling system, disconnect heater hoses from tubes in engine compartment and apply compressed air to upper tube and catch coolant from heater core coming out of bottom tube.

Negative battery cable
Positive battery cable and remove the battery
Coolant recovery tank cap to relieve the pressure from the system
Coolant
Heater hoses from (at) the heater core
Heater core tubes-to-chassis grommet

Remove the storage compartment on driver-s side.

From inside passenger compartment, remove bolts and brackets from heater core tubes.

Slightly pull the heater core from the A/C-heater housing.

Pull two coolant lines out of the heater core.

Remove the heater core.

If the heater core cannot be pulled out of the A/C housing, loosen the instrument panel cross member by removing or disconnecting the following:

Bolt at base of windshield (above meter cluster)
Loosen RH panel cross member bolts
Two bolts from bottom of instrument panel brace
ECM cover
Pedal bracket from cross member
LH instrument panel cover (push in steering column as far as possible)
Loosen 2 LH instrument panel nuts

Pull back instrument panel and cross member enough to allow heater core to be removed.

To install:

Installation is the reverse of the removal procedure, noting the following:

Install new clamps and O-rings at all connections
Before installing storage compartment on driver-s side, check for cooling system leaks
Ensure WOT stop of accelerator pedal is incorrect position

A8

Driver-s Side

Disconnect the negative battery cable.

Turn the ignition switch OFF.

Remove the windshield.

Remove the cowl panel.

Drain the cooling system into the clean container for reuse.

Remove or disconnect the following:

Engine-to-pump valve unit heater hoses. Drain and plug the openings
Electrical connectors from the pump valve unit

Remove the reinforcement plate (plenum) by removing or disconnecting the following:

Remove the intake hose from the air filter.
At the front wall of the plenum, remove the sound proofing mat.
Remove the reinforcement plate (plenum)-to-chassis nuts/bolts and the plenum

Remove or disconnect the following:

Loosen the heater hose holder screw in the plenum about 2 turns

Remove the knee bar by removing or disconnecting the following:

Open the glove box
2 knee bar trim screws
4 knee bar screws
Pull out the knee bar and disengage the latch
Electrical connector and remove the knee bar

Remove or disconnect the following:

Left support bolts and the retainer bolts; then, remove the left support and the retainer
Center console side trim
Passenger-s footwell air outlet
Passenger-s side heater hose clamps, move the heater hoses toward the plenum and discard the O-rings
Passenger-s side heater core-to-heater case clamp screws and the clamp
Passengers side heater core
Driver-s side shelf and center console-s side trim
Loosen the heater hose holder screws about 2 turns at the driver-s side heater core
Driver-s side footwell air outlet
Driver-s side heater hose clamps, move the heater hoses toward the plenum and discard the O-rings
Driver-s side heater core through the passenger-s side of the heater housing

To install:

Install or connect the following:

Driver-s side heater core through the passenger-s side of the heater housing
Move the heater hoses away from the plenum and install the driver-s side heater hose clamps using new O-rings
Driver-s side footwell air outlet
Heater hose holder screws at the driver-s side heater core
Driver-s side shelf and center console-s side trim
Passenger-s side heater core
Heater core-to-heater case clamp and the clamp screws
Heater hoses to the plenum using O-rings and install the passenger-s side heater hose clamps
Footwell air outlet
Center console side trim

Install the knee bar by installing or connecting the following:

Left support and the retainer and the left support bolts and the retainer bolts; then, torque the bolts to 16 ft. lbs. (22 Nm)
Electrical connector and install the knee bar
Knee bar and engage the latch
4 knee bar screws and torque to 22 inch lbs. (2.5 Nm)
2 knee bar trim screws and torque to 22 inch lbs. (2.5 Nm)

In the plenum, tighten the heater hose holder screw.

Install the reinforcement plate (plenum) by installing or connecting the following:

Reinforcement plate (plenum) and the plenum-to-chassis nuts/bolts
Sound proofing mat at the front wall of the plenum
Intake hose to the air filter.

Install or connect the following:

Electrical connectors to the pump valve unit
Engine-to-pump valve unit heater hoses

Refill the cooling system.

Cowl panel
Windshield

Connect the negative battery cable.

Operate the engine to normal operating temperature; then, check the climate control operation and check for leaks.

Passenger-s Side

Disconnect the negative battery cable.

Turn the ignition switch OFF.

Remove the cowl panel.

Drain the cooling system into the clean container for reuse.

Remove or disconnect the following:

Engine-to-pump valve unit heater hoses. Drain and plug the openings
Electrical connectors from the pump valve unit

Remove the reinforcement plate (plenum) by removing or disconnecting the following:

Intake hose from the air filter
Sound proofing mat at the front wall of the plenum
Reinforcement plate (plenum)-to-chassis nuts/bolts and the plenum
In the plenum, loosen the heater hose holder screw about 2 turns

Remove the knee bar by removing or disconnecting the following:

Open the glove box
2 knee bar trim screws
4 knee bar screws
Pull out the knee bar and disengage the latch
Electrical connector and remove the knee bar

Remove or disconnect the following:

Left support bolts and the retainer bolts; then, remove the left support and the retainer
Center console side trim.
Footwell air outlet

Place an absorbent cover on the floor of the car, under the heater core to catch any spilt coolant.

Passenger-s side heater hose clamps, move the heater hoses toward the plenum and discard the O-rings
Heater core-to-heater case clamp screws and the clamp
Heater core

Fig. Exploded view of the glove box, knee bar assembly and related components-A8

Fig. Exploded view of the heater cores and related components-A8

To install:

Install or connect the following:

Heater core
Heater core-to-heater case clamp and the clamp screws
Heater hoses to the plenum (using O-rings) and install the passenger-s side heater hose clamps
Footwell air outlet
Center console side trim

Install the knee bar by installing or connecting the following:

Left support and the retainer and the left support bolts and the retainer bolts; then, torque the bolts to 16 ft. lbs. (22 Nm)
Electrical connector and install the knee bar
Knee bar and engage the latch
4 knee bar screws and torque to 22 inch lbs. (2.5 Nm)
2 knee bar trim screws and torque to 22 inch lbs. (2.5 Nm)
Tighten the heater hose holder screw in the plenum

Install the reinforcement plate (plenum) by installing or connecting the following:

Reinforcement plate (plenum) and the plenum-to-chassis nuts/bolts
Sound proofing mat at the front wall of the plenum
Intake hose to the air filter
Electrical connectors to the pump valve unit
Engine-to-pump valve unit heater hoses