Removing, installing and checking auxiliary air heater element Z35 with auxiliary air heater control unit J604 — AUDI

🧭 Before you start

Fits: Audi A8 D4 (4H, 2010–2017)

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• The fitting location of the fuse can be found in the relevant current flow diagram .
• After detaching, insulate the two wires (B) and (C) separately (risk of short circuit).

📋 Procedure

1. Move the front right seat (front passenger's seat) as far back as it will go.
2. Switch off ignition.
3. Remove right footwell vent (front passenger's side) Removing and installing passenger side footwell vent.
4. ⚠ The air conditioner will not function properly if control motors and/or the corresponding connectors are interchanged Overview of control motors of air conditioner.The control motors and connectors are identical. If these are incorrectly installed or connected, the corresponding flaps can no longer be properly matched and/or activated.Mark control motors and connectors clearly before detaching or removing to prevent incorrect installation. — Remove air-intake box Removing and installing air intake box of front air conditioning unit.
5. Remove the right centre vent control motor V111Removing and installing right centre vent control motor V111.

6. ⚠ Risk of short circuit when disconnecting the power supply to the auxiliary air heater element Z35Remove the fuse in the power supply to the auxiliary air heater element Z35. — Interrupt the power supply to the auxiliary air heater element Z35 by removing the corresponding fuse (currently 150 A). [Note: The fitting location of the fuse can be found in the relevant current flow diagram .]
7. Unplug the connector (A) from the supplementary air heater control unit J604(D).
8. Check again using a voltage tester. There must not be any voltage between the connections (C) (positive) and (B) (negative) (danger of short circuit). [Note: To prevent interchange of the connections (C) (positive) and (B) (negative), the diameters are different (M6 thread and M8 thread on J604).If the connections ((C) and (B)) are incorrectly assigned, J604 can no longer regulate the current and there will be a constant flow of current through Z35 (unregulated with maximum heat output).]
9. Detach the two wires (B) and (C) to J604.
10. After detaching, insulate the two wires (B) and (C) separately (risk of short circuit).
11. Remove bolts (E).
12. ⚠ The auxiliary air heater element Z35 may be hot.If Z35 has been activated prior to removal, do not touch Z35. — Pull J604(A) (with Z35(B), cannot be checked and replaced separately) out of the mounting slot (C) of the air conditioning unit.
13. Check the mounting slot (C) of the air conditioning unit for contamination with Z35(B) removed and clean if necessary.
14. Check the partition between the left and right side in the air conditioning unit by way of the mounting slot (C) for Z35.
15. Slide Z35(B) with J604(A) into the mounting slot (C) of the air conditioning unit.
16. Only install Z35(B) in the mounts (F) of the air conditioning unit with the rubber bushes (D) at the lugs (E).
17. Fit bolts (E).
18. Attach the two wires (B) and (C) to J604.
19. Re-install all components removed in reverse order.
20. Perform basic setting and final control diagnosis for the air conditioner in "“Guided Fault Finding”" mode. [Note: The control motors on this vehicle are equipped with electronics. A new control motor only learns its position at the air conditioning unit in the course of basic setting and can then be activated by the air conditioner front operating and display unit, Climatronic control unit J255 (all control motors are identical at present) in "“Guided Fault Finding”" mode.While you are performing the basic setting, the control motors are assigned and adapted in accordance with the series connection of the wiring. If the sequence is not as specified, the control motors will not be adapted properly and the flaps will not be controlled correctly Overview of control motors of air conditioner.]
21. Interrogate the event memory of J255 and erase any faults displayed in "“Guided Fault Finding”" mode.
22. After installation, check the activation and operation of Z35 by way of J604 if applicable in "“Guided Fault Finding”" mode and Checking electric supplementary heater.

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