07 century HDWY + - ??? air dump?

Per the F/liner online PDF for your truck:
The link can be found here, and I recommend you reading it thoroughly if there are no manuals in the rig.

http://globalautousa.com/downloads/manuals/drivers/century-coronado.pdf
Here is the relevant section:


Dash Switches
The following dash switches (Fig. 2.70) are used to
control the CWS and optional SmartCruise.
· Headway Alert (HDWY ALERT): This switch
turns on the CWS. On most systems, the CWS
will turn on automatically when the ignition is
turned on. The switch is backlit by a green light
that indicates the system is on.
If the system is equipped with the optional
SmartCruise, the switch will not be installed.
· Headway Control (HDWY CNTL): This switch
is installed on vehicles with the optional Smart-
Cruise. When this switch is pressed the light
comes on to indicated that the vehicle is in
SmartCruise mode. It has the same function as
the SPD CNTL switch, which will be installed
on vehicles without SmartCruise. The switch
will be backlit by a green light when the Headway
Control is on.
· Resume/Accelerate - Set/Coast (RSM/ACC -
SET/CST): This switch works the same as it
05/08/2000
1 2
f610414
3 4 5
1. Headway Control Switch
2. Resume/Accelerate - Set/Coast Switch
3. Headway Alert Switch (on vehicles without
SmartCruise)
4. Headway Adjustment Switch
5. Headway Volume Switch
Fig. 2.70, Dash Switches for CWS and optional
SmartCruise
Instruments and Controls Identification
2.57
does on conventional cruise control. On vehicles
with SmartCruise, the speed will change
if necessary to maintain the set headway.
· Headway Volume (HDWY VOL+/-): This
switch adjusts the volume of the headway
alerts and other audible alerts from the CWS.
The speaker volume ill reset to maximum volume
when the system turned off and back on
again or the ignition is turned off and back on.
· Headway Adjustment Switch (HDWY+/
HDWY-): This switch will adjust the headway
for alerts. When the system power is reset, the
headway will default back to the maximum distance.
For vehicles with SmartCruise, the headway
adjustment will determine the headway the vehicle
will maintain from other moving vehicles
in the same traveling lane of your vehicle.
Cruise control must be set for the headway to
adjust.
Headway Alerts
The ICU displays indicator lights and messages that
advise of multiple warning levels, system power, system
failure. See Fig. 2.71 and Table 2.6.
The speaker provides audible alert tones to warn of
closing on an object ahead and when equipped with
an optional side sensor, of objects alongside when
the turn signal is activated in preparation for a lane
change. Additional tones indicate speaker volume,
system failure and data extraction pass or fail.
The "object ahead" alerts given by the system are
based on headway to the vehicle ahead, that is the
time required by the host vehicle to travel ahead and
reach the vehicle ahead. A simple way to figure the
headway is to look when the vehicle ahead drives by
a certain object, like a traffic sign, and then start
counting the time required to reach the same sign. If
the count reaches three, then the headway is a
3-second headway. A more precise method of determining
the headway would be to use a stopwatch
rather than counting.
For example, if the headway is 3 seconds and the
vehicle speed is 55 mph (88.5 km/h), then the distance
to the vehicle ahead is 242 ft (74 m). If the vehicle
speed is reduced to 40 mph (64 km/h), the distance
is 176 ft (53.5 m) for a 3-second headway.
Audible and visual headway alerts are as follows:
· When a moving object is detected in the travel
lane and is less than 350 ft (107 m) from the
front of the vehicle, the HDWY DETECT light
will illuminate on the ICU. No warning tone will
sound.
· When a moving object is detected in the travel
lane and it has a headway between one and
two seconds, the HDWY DETECT light will illuminate
and a message will appear on the ICU.
A warning tone will sound.
· When a moving object is detected in the travel
lane and it has a headway is between 1/2 second
and 1 second, the HDWY DETECT light
will illuminate and a message will appear on
the ICU. Warning tones will sound also.
If the headway is increasing, no tone will
sound. If the headway is decreasing, double
tones will sound. Within a 1/2-second or less
following interval, opening or closing, the tones
will repeat twice per second.
· If a stationary vehicle or object or an object
moving at least 20 percent slower than your
vehicle is detected within 220 feet (67 meters)
and within 3 seconds, HDWY DETECT lamp
will illuminate, a message will be displayed,
and double tones will sound. This warning
overrides all others and is not affected by the
headway setting.
· If your vehicle is traveling less than 5 mph (8
km/h) and an object is detected less than 15 ft
(4.5 m) in front of your vehicle and the closing
rate is less than 2 mph (3 km/h) but more than
1/2 mph (1 km/h), the HDWY DETECT lamp
will illuminate, a message will be displayed,
and a low-frequency double tone will sound.
FASTEN SEATBELTS
0000432 MILES
2
f610412
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1. SmartCruise Lamp (HDWY CRUISE)
2. Headway Alert Lamp (HDWY DETECT)
3. System Failure Lamp (HDWY FAIL)
Fig. 2.71, ICU Displays
Instruments and Controls Identification
2.58
ICU Display Messages
ICU Message Description
Speed Set: 55 mph (88.5 km/h)
Headway Set: 3.0s
The Speed Set and Headway readings will display when the vehicle speed
drops 5 mph (8 km/h) below the set speed. The vehicle will automatically
accelerate to the set speed when the headway is clear up to the Headway Set
distance.
WARNING
HEADWAY FAILURE
CWS has failed. HDWY FAIL lamp will also illuminate.
WARNING
CRUISE OFF
Vehicle speed is below 30 mph (48 km/h), minimum cruise speed. An audible
tone will also be heard. The cruise is off.
HEADWAY RANGE
f601895
Displays current headway setting (maximum setting displayed).
HEADWAY ALERT VOLUME
f601896
Displays current audible tone volume (maximum volume shown).
HEADWAY EVENT DATA
WAS SAVED
Accident reconstruction segment was saved.
HDWY EVENT DATA NOT
SAVED, MEMORY FULL
Second accident reconstruction segment was not saved. Only one accident
reconstruction segment may be saved.
OBJECT AHEAD
f601891
Displayed if an object is detected and has a headway 0.5 to 1 second. Also
displayed if a very slow or stationary target is detected in the vehicle
headway.
OBJECT AHEAD
f601892
Displayed if an object is detected and has a headway of more than one
second and up to 2 seconds.
OBJECT AHEAD
f601893
Displayed if an object is detected and has a headway of more than 2 seconds
and up to 3 seconds.
APPROACHING OBJECT
f601894
Displayed if an object is within 15 ft (4.5 m) and the vehicle is traveling less
than 5 mph (8 km/h)
Table 2.6, ICU Display Messages
NOTE: All warnings apply only to objects within
the maximum headway range and in your lane.
Proximity alert tones and vehicle-closing 1- to
2-second following interval tones are configured
items. All tones, except the 1/2-second alert, are
disabled in sharp turns or when the brakes are
applied. If the configuration permits, the
3-second alert level may be adjusted with the
headway adjustment switch (HDWY +/HDWY -)
on the dash. A single low-frequency tone
sounds when a system failure is detected. A
medium-frequency tone sounds when the volume
control level is changed. Successful downloading
of Vehicle Information Management System
(VIMS) data will cause a double tone to
sound. Unsuccessful downloading will cause a
low-frequency tone to sound.
Instruments and Controls Identification
2.59

 

Guess that's NOT the switch to "dump" the air ride suspension.

 

Thats possible, you could have a dump installed.

 

Sounds like it doesn't have a dump valve installed indeed.
You can either get an OEM switch and plumb it in, or get a 12v solenoid and mount it to the frame, then plumb that in and just run 1 wire to the cab switch. I have installed them both ways, and the solenoid was the easier way to install.
Looks like it came from a fleet, if they had "smart cruise" but no dump valve. Make 110% sure it has the maintenance records with it, as a lot of fleets run a very extended oil change program. Not cool IMHO.

Martin