VW used to have a box that was tied into the speedo cable, that would automatically have the light come on every 15 k miles. It would be behind the firewall - the area where you would find the wiper mechanism, and the blower for the cabin.
I don't know for how long they used this gadget, but what the heck...thought I would mention it - maybe you'll get lucky.

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D