The quest for enabling the compass display in a 2018 Volkswagen Alltrack S led to a deep dive into the erWin service documentation, revealing some intriguing findings about the Vw Compass system. This investigation focuses on the antenna hardware and associated modules responsible for compass functionality.
Decoding the Antenna Network
The Golf Mk7 platform, upon which the Alltrack is based, boasts a complex network of antennas. While no single antenna is specifically designated for the VW compass, evidence suggests it’s likely integrated within the Roof Antenna (RX5). This aligns with VW’s typical placement of the compass antenna.
The RX5 antenna connects to either the Front Information Display Control Head (J685) or the Information Electronics Control Module 1 (J794), determined by the vehicle’s optional equipment.
Module Mysteries: J685 and J794
In models equipped with the Discover Media system (SE and SEL trims), J685 and J794 are distinct components. However, the base S model, featuring the Composition Color head unit, appears to combine these modules within the dashboard.
J794, the Information Electronics module, typically resides as the CD player unit in the glove compartment. Notably, the Alltrack S lacks this component.
Further investigation revealed that the J794 module in an Alltrack SE (part number 3Q0 035 844) is indeed the CD player with coaxial antenna jacks.
Contrastingly, the Alltrack S has a single Information Electronics module (5G6 035 868), presumably the combined display and module unit in the dashboard.
The Case of the Missing Antenna
A crucial discovery was made upon inspecting the Alltrack S’s roof: the antenna is a dummy, devoid of any wiring.
This absence, potentially a cost-saving measure, coincides with the 2018 model year’s infotainment system changes and the omission of full VW Car-Net functionality in the S trim. Car-Net buttons, present in 2017 models and the 2018 Alltrack SE, are absent in the Alltrack S.
Exploring Alternative Solutions: The J949 Module
The wiring diagram indicates the RX5 antenna can also connect to the J949 module (“Control Module for Emergency Call Module and Communication Unit,” likely Car-Net). Located behind the instrument cluster, this module is responsible for telematics and GPS data.
This raises the question: could installing a J949 module (5QE 035 285) with only the compass input enable the compass display? This remains a theoretical possibility, warranting further investigation.
Conclusion: The VW Compass Conundrum
The lack of a physical antenna and the integrated nature of the infotainment system in the 2018 Alltrack S present significant challenges to enabling the VW compass display. While the J949 module offers a potential avenue for exploration, it’s clear that activating the compass in this model isn’t a simple VCDS tweak as in previous years. The investigation highlights the complexities of modern automotive systems and the impact of cost-saving measures on feature availability.
