Removing and installing supplementary air heater element Z35 (with supplementary air heater control unit J604) — AUDI

🧭 Before you start

Fits: Audi A3 (8P, 2003–2012)

• Special tools named: VAS 5051

Don't miss

• Using a voltage tester, for example, check that there is no longer any voltage between the connections (C) (positive) and (B) (negative) (danger of short circuit).
• Detach both wires (B) and (C) to the supplementary air heater element Z35 (tightening torque of hexagon nuts 6 Nm) and insulate the connection points (danger of short circuit).

🔩 Torque settings

Values can differ between engine variants — check the code stamped on your block.

ℹ️ Always cross-check the exact figure against your vehicle's factory manual before final tightening — a wrong torque can damage the engine. These values are extracted from workshop data and may not cover every variant or revision.

📋 Procedure

1. Remove the driver's storage compartment. General body repairs, interior68
2. Remove the centre console. General body repairs, interior68
3. Remove the left footwell vent (A) (driver side). General body repairs, interior68
4. Remove the holder (B)General body repairs, interior68.
5. Remove the 4 bolts (A) and detach the cover (B). [Note: There are different versions of the cover (B) (for vehicles without or with electric supplementary heater) Electronic parts catalogue.If the lever to the left temperature flap is positioned such that the upper bolt (A) is not accessible, switch on the ignition and select a different temperature setting (on the operating and display unit, Climatronic control unit J255 for the left side, e.g. setting "“Hi”").]

6. Switch off ignition.
7. Interrupt the power supply to the supplementary air heater element Z35 by removing the corresponding fuse (currently 100 A). The fuse fitting location is indicated in the relevant current flow diagram
8. Unplug the connector (A) from the heater element (D).
9. Using a voltage tester, for example, check that there is no longer any voltage between the connections (C) (positive) and (B) (negative) (danger of short circuit).
10. Mark the two wires to the supplementary air heater element Z35 (danger of interchange, vehicles with supplementary air heater control unit J604 only). [Note: If the connection assignment is interchanged, the supplementary air heater control unit J604 can no longer regulate the current and there is a constant flow of current through the supplementary air heater element Z35 (with maximum heat output and no regulation).]
11. Detach both wires (B) and (C) to the supplementary air heater element Z35 (tightening torque of hexagon nuts 6 Nm) and insulate the connection points (danger of short circuit). — 6 Nm (4.4 lb-ft)
12. Pull the supplementary air heater element Z35(A) (together with the supplementary air heater control unit J604(B), cannot be checked and replaced separately) out of the air conditioning unit (heater).
13. Switch off ignition.
14. Remove the hexagon nut (A) (tightening torque 6 Nm). — 6 Nm (4.4 lb-ft)
15. Unplug the connector (B) from the supplementary air heater element Z35(C).
16. Pull the supplementary air heater element Z35(B) out of the air conditioning unit (heater). [Note: The hexagon nuts at the two wiring connections (B) and (C) to the supplementary air heater element Z35 are tightened to 6 Nm (excessive torque would damage the electronics of the supplementary air heater element Z35).The hexagon nut (A) at the connector (B) and the earth connection of the supplementary air heater element Z35(C) is tightened to 6 Nm. Excessive torque could damage the electrics of the supplementary air heater element Z35.]
17. If applicable, check actuation and operation of the supplementary air heater element Z35 after installation "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051 (vehicles with air conditioner) and (vehicles with no air conditioner).

Other AUDI procedures

• Removing and installing toothed belt – Audi · 56 torque figures
• Removing engine – Audi A8 D3 · 41 torque figures
• Removing camshaft timing chain from camshafts – Audi A6/A7 C7 · 38 torque figures
• Installing engine – Audi A8 D4 · 36 torque figures
• Removing and installing camshaft timing chain · 29 torque figures