Paul,

I think that the 86 is basically the same as the 85, and Helga is also factory equipped. There is a module under the glove box (right beside the fuel pump relay). The servo is under the hood on the passenger side, and then you have the multifunction switch on the turn signal lever. There is a vacuum disconnect switch on the brake pedal as well.

As I understand the system (and I may miss a couple of items), the module receives its signal from a speed sensor on the speedometer. It measures the pulses and converts this information to a frequency reading. when you press the set portion of the multifunction switch, the module remembers this speed frequency, and tries its best to maintain that frequency. It orders the servo to open or close the vacuum motor control in order to keep the frequency within its limits. The servo operates the throttle drum, either opening the throttle valve, or closing it to match the signal that the module is receiving to the remembered frequency. The system also has a vacuum defeat switch that is activated by pressing the brake pedal, which will put the frequency out of limits, causing the system to fail off. There is also a mercury switch that will shut the system down electrically should the car tip further than the switch will allow.

Now, when you tried to shut the system down by touching the brake pedal, the system did not recognize the vacuum dump. When you tried to shut it off with the switch, it ignored that signal as well. It sounds as if the module has either suffered a failure (perhaps a diode burned shut) or you have lost a necessary ground connection. When you turned the ignition off, with the cruise switch in the off position, the module did not energize, and so had no frequency to remember, so it stayed off. If you have a spare module, I would try switching it out. It should take no more than a couple of minutes to do this. A test drive will tell you quickly if that was the fix. If not, then you need to check the connector at the speedo, and proceed to search the grounds for the system.

I'll be watching to see what you find.

Bill