When I open the rear hatch the light should come on. It almost never does unless I leave the lid open for a while, then it works. The bulb and switch are therefore working but why not when they should? There's no obvious way to trace the wiring or even find the switch. I've removed the lamp and checked for corrosion - like new. ???
Cruise control engages about every 20th time I try, then it performs perfectly for a few minutes and drops out. We've replaced the brake pedal switch, the steering column switch, the vacuum pump, and all the rubber tubing - no change whatever. Seems like an electrical connection failure but experienced Audi mechanics can't fix it.
Question: is there a control module for the cruise control, or is it operated from the central control for the engine? We replaced the ECU a year ago and the cruise control started failing soon after but the mechanics don't know the answer.
Operates perfectly when it will engage, very seldom, then suddenly disengages and won't come back for hours. Replaced brake switch, all hoses, vacuum pump, stalk switch. Seems to be electrical to me, but maybe it's a problem in the basic ECU or does it have an independent controller?