Resistance testing of a new 04671929AB cruise control lever.
Measurements by Lawrence Glaister VE7IT (firstname.lastname@example.org)
October 9 2010.
Pin to Pin Resistance
Lever position 1-2 1-3 2-3
============== ======= ======= =======
Normal 20.5k 40.8k 20.5k
Cruise on/off 6.19k 6.66k 0.51k
Cancel 3.28k 4.46k 1.21k
Resume 1.71k 10.49k 8.82k
Set 0.79k 5.12k 4.37k
-in all cases, column 2 is approx the sum of column 1 and 3
-column 1 has an interesting sequence close to 6.4k, 3.2k, 1.6k, 0.8k
-ohm meter polarity doesnt seem to matter indicating the
device consists of switches and resistors (no solid state devices)
-how many resistors and how many switches and what is the configuration
to make this 3 terminal network function?
-I made a test connector using a cut down computer 3.5" floppy drive power
connector (cut the 4 pin plug down to 3 pins using exacto, file, or grinder)
This could be used instead of the factory $70 harness, but I dont want to have
insurance or guarantee issues, so I suggest using the factory harness to install
the cruise option.
Possible control configuration....
Pin 2 may be grounded and pin 1 and 3 may be pulled up to 5v by the ecu by say 10k.
All control inputs use dual redundancy... in other words for a state change to be
recognized, 2 switches must close and create the right voltages on pins 1 and 3.
This follows similar logic to the throttle pedal position sensor using multiple
channels of sensor to verify valid position sensing and to reject noisy or invalid
commands. At this point, I don't really want to break the switch open to look at
the internal logic or to try and measure the pin voltages with the engine on
doing 30+mph with the air bag hanging loose in my lap. The above table should
still be useful for troubleshooting cruise control switch problems.
The control could be implemented with a fixed 20.5k resistor from pin 1 to 2
and a 20.5k resistor from pins 2 to 3.. this would satisfy the normal state
condition and enable the ecu to recognize that the cruise option lever was
installed. Each of the other states could be created by switching a set of
resistors of the appropriate values across the 2 resistors mentioned above. This
would require 2 switch contacts for each state or a total of 8 contacts and a
total of 10 resistors. It may also be possible to reduce the network to fewer
resistors by using series resistors and a creative switching scheme. Without
opening the cruise switch, my guesses are purely conjecture. Anyone willing to
dissect a cruise control lever?