wingless' '86 911 Carrera Cruise Control Adjustment Questions

[winglesss]

The optional OEM cruise control on my gorgeous new-to-me 1986 911 Carrera Targa is functional but doesn't perform to my liking.

There are four positions on the cruise control stalk. These are: UNCHANGED (resting position); SET / ACCELERATE (lift stalk); RESET (lower stalk) and CANCEL (pull stalk).

All those functions work as-described.

The issue has been that once the cruising velocity is set, then there will be a up / down "ripple" in the velocity. The speed will droop, then a short while later there will be a large throttle application until the setpoint velocity is restored, then that cycle repeats.

My hope had been that elimination of the small amount of existing cable slack between the throttle valve and the cruise control actuator would have eliminated this surging, but there was no discernable effect.

My secondary hope is that the "old school" cruise control module would have manual electrical trimpot adjustment screws to change the settings for gain, response speed and the like, but instead the module, located under the stereo has zero obvious adjustments available. The module has a staked shut enclosure box.

What is the method for "tweaking" this cruise control to have acceptable results? (Thanks in-advance for any / all assistance.)

At this point I am leaning to bend open the six staked closures retaining the aluminum box to the plastic connector plate.

[winglesss]

The six folded edge stakes were manually opened up to permit the cruise control module to be slid out of the aluminum extrusion box.

Once the guts were exposed it was determined that there are not any adjustments on that controller board. All of the components are through hole devices, soldered onto one side of a circuit board.

Both sides of the circuit board are protected from degradation by a thick conformal coating.

... still open to suggestions for functional improvements on the cruise control...

[mysocal911]

Originally Posted by winglesss

The optional OEM cruise control on my gorgeous new-to-me 1986 911 Carrera Targa is functional but doesn't perform to my liking.

There are four positions on the cruise control stalk. These are: UNCHANGED (resting position); SET / ACCELERATE (lift stalk); RESET (lower stalk) and CANCEL (pull stalk).

All those functions work as-described.

The issue has been that once the cruising velocity is set, then there will be a up / down "ripple" in the velocity. The speed will droop, then a short while later there will be a large throttle application until the setpoint velocity is restored, then that cycle repeats.

My hope had been that elimination of the small amount of existing cable slack between the throttle valve and the cruise control actuator would have eliminated this surging, but there was no discernable effect.

My secondary hope is that the "old school" cruise control module would have manual electrical trimpot adjustment screws to change the settings for gain, response speed and the like, but instead the module, located under the stereo has zero obvious adjustments available. The module has a staked shut enclosure box.

What is the method for "tweaking" this cruise control to have acceptable results? (Thanks in-advance for any / all assistance.)

At this point I am leaning to bend open the six staked closures retaining the aluminum box to the plastic connector plate.

Your cruise control module is bad and needs to be repaired.

[winglesss]

Originally Posted by mysocal911

Your cruise control module is bad and needs to be repaired.

Thanks, suggestions for service provider? This guy charges $100 flat rate.

This topic has good info. This topic too.

FWIW, opening the enclosure had the distinct smell of failed electronics.