Background

Rear spoiler motor and control module

The rear spoiler doesn’t survive our Ute transformation, but its demise has a few implications that must be addressed.

The spoiler moves via an electric step motor controlled with a separate, but integrated, electronic module.

Spoiler operation uses different logic circuits that require speed data input:

  1. if speed under 12mph → can raise manually, dash indicator blinks
  2. if speed exceeds 12mph → automatically lowered if raised before
  3. between 12-43mph → can raise/lower manually in single step
  4. if speed under 10mph → automatically lowered if raised before
  5. if speed exceeds 45mph → automatically raised, manual switch disabled
  6. if speed exceeds 85mph → sunroof automatically closed
  7. if speed 0mph → can raise/lower manually in steps

All of this complexity is handled by the following wiring schematic.

The internal electronics are proprietary to Volkswagen, so we can only make educated guesses about the reason for some of the connections. It appears that the ABS and comfort modules attach to the spoiler module for wiring convenience; that is, they all share some fuses and provide switched and unswitched B+ power.

Vehicle speed is a critical data input coming from the instrumental cluster module. The sunroof module connection enables the automatic partial closing of the sunroof when triggered by vehicle speed.

Data K-line

The data link diagnostic wire, referred to as K-line defined by ISO9141, is a low-speed serial communication system — independent from the high-speed CAN-Bus dual wire protocol — that reports any module faults and enables programming the master ECM for different spoiler opening speeds (a pre-2002 version opened up the spoiler at about 90mph instead of 45mph, for example). The GLX spoiler apparently has speed zones that open the spoiler in ECM-controlled four-step increments:

  1. 0-12mph
  2. 12-78mph
  3. 78-90mph
  4. over 90mph

In any event, as far as the Ute project goes, this is all a bit academic. The K-line was eliminated from the CAB-Bus specification about fifteen years ago. The K-line transmission is in the form of a square wave triggered when voltage is between 7 and 11 volts; voltages above this band may cause either DLC fault codes or prevent OBD2 scan tools from working properly. Probably the best method for “disposing” of the K-line is wrap it up with tape to prevent any voltage along the wire.

Removal impact

The big question of course is what happens when the spoiler control module is removed from the car. All the switching in the spoiler control module is ground activated:

  • pin 3 grounded by switch –> opens spoiler manually via motor relay and also removes pin 10 ground (normally closed) to trigger warning light
  • pin 5 grounded by switch –> closes spoiler manually via motor relay (in steps if speed < 10mph) and restores pin 10 ground when fully closed to turn off warning light
  • pin 6 grounded by VSS signal if speed over 45mph –> sunroof partially closes (full sunroof closing controlled by separate logic circuit independent of spoiler)
  • pin 10 not grounded –> spoiler warning light on

Thus, the impact of removing the spoiler module interrupts the ground from the spoiler warning wire and turns on the dash indicator light permanently! In addition, the spoiler switch under the dash becomes inactive and the partial sunroof closing safety feature is disabled because the VSS signal path is cut.

Functional re-purposing

The spoiler rocker switch hidden under the dash and the spoiler warning light can simply be disabled and forgotten.

Spoiler switch back

Spoiler rocker switch

Eaton 17-22145 switch plug

A more complete esthetic solution would be to remove the disabled switch and cover the opening with an Eaton 17-22145 plug (a standard 37x21mm toggle switch size).

On the other hand, there might be some future function best handled by the OE toggle momentary switch (to open/close or lock/unlock something). Or the existing switch could be swapped out for a non-momentary function (optimally in the rear of the Ute to make use of the existing harness).

While the blank spot on the instrument cluster for the spoiler warning causes no inconvenience, the spoiler warning could be re-wired to indicate some other operational condition although it would have to be consistent with the existing spoiler icon.

Dual rear camera setup

One possible re-purposing of the spoiler switch would modify it for a dual rear camera setup: one camera for backup located near the license plate, and one camera for cargo co-located with a third brake light above the rear window. This arrangement would only use one video input on a popup video screen entertainment head unit (replacing the existing radio/cassette player) so a third front camera could also be deployed.

A dual camera re-wiring can be accomplished with relatively minor modifications. A piggypack fuse provides positive current to the spoiler rocker switch (replaced with a same size non-momentary rocker) that uses the existing harness connection at the top of the rear window glass to turn on a cargo camera. A connection between pins 5 and 10 illuminates the old spoiler warning whenever the cargo camera is active. Otherwise, the backup camera is active and no warning is displayed.

Meanwhile, the spoiler motor fuse is removed rendering the pin 2 wire connection inactive. Wrapping up the end of the pin 12 wire eliminates any problems with CAN-Bus communication. Terminating the ground pins 4 and 11 has no impact, nor does disconnecting the 8 and 9 positive leads. The VSS signal is only incoming, so removing pin 7 leaves all other VSS functions unaltered. Finally, disconnecting pin 6 to the sunroof will not change its operation apart from the partial closure feature triggered at speeds over 45mph.

Disabled switch but truck lighting indicator

If the spoiler switch is disconnected (and the motor assembly removed), the warning indicator will remain illuminated. A possible solution is to re-purpose this warning as an exterior truck bed illumination indicator (bed lighting is difficult to see in daylight). To accomplish this, the warning light wiring must be incorporated into the heated rear window switch circuitry.