SparePartAlam

On a 2005 Octavia Mk2 (1Z5 estate) with dual-zone Climatronic, the wiring is different from the manual Climatic setup because there is no separate 4-speed resistor pack (N24) in the ducting. Instead, the PWM blower control module (J126) is clipped directly onto the fresh air blower motor assembly (V2), and the whole unit is fed by a single 6-pin connector (T6z) behind the glovebox. 1. Factory wiring and pinout at the 6-pin blower plug (T6z on J126) - Pin 4 (T6z/4, thick 4.0 mm² red/black or red/white wire): permanent 12V battery feed (Terminal 30a) via splice B322 from fuse SC22 (40A) in the dash-end fuse box. On some later MY2008+ diagrams this 40A blower fuse moves to SC40 or SC38, so check both 40A maxi fuses in the dash-end panel. - Pin 3 (T6z/3, thick 4.0 mm² brown wire): main earth (Terminal 31) via harness splice 374 to earth point 617 on the lower right A-pillar behind the kick trim. - Pin 1 (T6z/1) and Pin 2 (T6z/2, thin 0.35/0.5 mm² wires): PWM speed demand signal and diagnostic feedback between the blower regulator (J126) and the brown 16-pin plug (T16l) on the back of the Climatronic panel (J255, pins T16l/15 and T16l/6, routed through the 10-pin coupling plug T10e behind the dash). - Climatronic panel (J255) supply fuses: SC4 (10A) for switched ignition (15a) and SC16 (10A) for permanent memory supply (30a). - From the J126 controller, two short heavy fly-leads (red and black) plug straight onto the brush tabs of the V2 blower motor. 2. How to test why it is cutting out intermittently 1) Check voltage under load at T6z Pin 4 and Pin 3: unplug the 6-pin T6z connector under the passenger footwell foam cover (twist the locking tab and rotate the motor assembly clockwise to drop it). Put a 21W/55W headlamp bulb across Pin 4 (+12V) and Pin 3 (earth). If the bulb lights brightly and does not flicker when you wiggle the plug or fuse SC22, your main power and A-pillar earth (617) are sound. 2) Check the PWM signal on Pin 1 / Pin 2: with the ignition on and the Climatronic fan turned from minimum to maximum, the control voltage from J255 on the thin control wire should vary smoothly with fan speed demand. 3) Why intermittent failure happens on a 2005 Mk2: - Sticking brushes / water ingress in V2: rainwater getting past a blocked scuttle drain or poorly seated pollen filter cover drips onto the top bearing of the blower. When the bearing drags or the carbon brushes stick, current draw spikes and the J126 controller trips its internal thermal cut-out (and usually logs fault code 01273 - Fresh Air Blower (V2): 010 Open or Short to Plus, or 003 Mechanical Failure, in VCDS Address 08 Auto HVAC). - Dry solder joints inside J126 (3C0 907 521): the regulator module on the fan frame suffers from cracked MOSFET legs after years of heat cycling. You can test the motor (V2) on its own by unplugging the two heavy motor tabs from J126 and feeding fused 12V directly to the motor pins. 3. Part numbers to watch if you buy a replacement If the commutator is worn or the bearing is dry and you decide to replace the unit, make sure you get the right-hand-drive Climatronic version: - Complete RHD Climatronic blower with regulator: 1K2 820 015 (superseded by 1K2 820 015 A, D, G and H). - Blower regulator (J126) on its own: 3C0 907 521 / 3C0 907 521 F. - Avoid 1K1 820 015: any part starting 1K1 is left-hand drive; the blades and housing scroll run in the opposite direction and will barely push any air through a UK right-hand-drive heater box. Also avoid 1K2 819 015, which is the bare 2-pin motor for manual Climatic without the J126 controller mount.