Eric,

Thanks for the detailed HOWTO.

I installed a similar unit a while back and it seems to work fine on my '84.

1) Why did you use the magnetic pickup?  I thought that was only
   necessary with an automatic transmission?  My installation senses
   engine speed through the coil wire.

2) A disengage down hill is a safety feature.  The idea is that the
   car shouldn't continue to speed along, or increase speed over some
   length of time with that the cruise thinks is a closed throttle.  I
   haven't experienced it with my current cruise control, but I did
   experience it with the previous one on long mountain descents.

3) Just a week ago, I made a wiring change in my installation to
   reflect behavior that I was used to in all my previous cruise
   control installations.  The AudiVox unit acts like most factory
   installations in that there is no provision to disengage the cruise
   without losing its setting except by using the brakes.  All of my
   aftermarket units, until the AudioVox, retained the last setting
   when switched off and then back on again.  Only using the set key,
   or turning off the ignition unset the unit.

   I measured the current draw of the unit and found it to be less
   than 100 milliamps when disengaged, so I reasoned that I could
   leave the unit active all the time.  So I made the following wiring
   modifications.

   a) I connected the power to the unit from the control, and
      connected directly to the fused power source.  This leaves the
      unit powered on any time the ignition is on.

   b) I disconnected the wire from the unit that senses brake light
      battery voltage and connected it to the switched power source
      from the control unit.  This is the place the cruise unit
      power lead was originally connected.  This change supplies the
      cruise with brake light reference voltage only when the cruise
      switch and the ignition switch is on.

   c) I added a diode in the wire from the brake lights to the cruise
      unit.  I don't know whether this was necessary, but with the
      ignition or cruise switch off, stepping on the brake pedal
      causes this lead to go to 12 volts.  With my other
      modifications, the brake light reference voltage is zero and bad
      things could happen to the cruise.  The diode blocks reverse
      current flow.

      I determined that the current flow was out of the control unit,
      so the arrow on the diode should point toward the brake lights
      and away from the cruise unit.

   With the above modification the cruise acts the same as before, but
   will return to its last speed setting if the unit is on and resume
   is pressed.  It does lose its setting on ignition off.

Thanks again for sharing.

Mike      '84 GL  '58 Isetta (no cruise)