Air throttle and related systems

[Ralph L. Fullenwider]

Hello everyone:

On a thread I started a few weeks ago on the air throttle and high idles
systems, it seemed unclear as to what happens and when on these systems. I
contacted Benny and received the "prints" on these systems and have
attempted to do a write up for everyone who is interested. Below is the
sequence of operation, as I interpret the prints.

Air Throttle system/Cruise control/air break interaction

Throttle control:
1. Coach air is supplied to the air throttle control valve (gas peddle)
which modulates the amount of air passed to the double check valve to the
throttle air cylinder.

2. There is an exhaust port on the air throttle vale that exhausts excess
air when less throttle is called for,

3. or the air break is used dumping all throttle air off the throttle air
cylinder.

Cruise control:

1. Coach air supplied to the pressure reducing valve, from 120 psi to 80 to
90 psi.

2. From the pressure regulating valve to the dual valve on or near the
Bendix cruise control module. The module controls the position of the
shuttle in the valve to call for more, or less air going to the TR-3
inversion valve.

3. From the TR-3 inversion valve to the double check valve,

4. and from the double check valve to the air throttle cylinder

5. There is an exhaust port on the TR-3 inversion valve to release the air
when the air break is pressed, exhausting the cruise control air to
atmosphere, kicking out the cruise control.

6. The Bendix memory holds the electronic sense position to return the dual
valve back to the preset position for resume.

7. Turning off the cruise control power switch or the Coach key switch,
resets the Bendix control module memory.

Air break interaction:
This is stated in the various actions in the above for the Throttle control
and the cruise control.

Throttle air cylinder:

1. Pulls back on the attached cable to the throttle control on the engine.

Of course, all this is air controlled by the 60 psi air switch, so the
front air tank, rear air tank and the "wet" tank must have reached 60 psi min.

Air systems:

1. The "wet" tank is supplied air from the coach compressor through the
governor and the air drier.

2. The front and rear "break" tanks are supplied by the "wet" tank which
there is a check valve between the "wet" tanks and the front and rear
"break" tanks.

3. All air systems in the Coach; air step/ride height air bags/throttle
control/up-down co-pilot step well cover/air ride seats/seat slide/water
winterizing blow out system, and so forth, are suppled from the "wet" tank
only.

This is all separate from the "high idle" control system.

The cruise control system on the FC's is similar to the PT's but have a
different control cylinder. That cylinder has electronic positioning sensor
which pulls the cable going to the bell crank on the cable/manual throttle,
and there are two solenoids that deal with the "clutch" part of the old
Bendix control. The "clutch" part interacts with the transmission neutral
switch to get the selectable "high idle" electronically.


Safe travels,

Ralph and Charolette Fullenwider
Ralph's RV Solutions, Duncan, Oklahoma
http://home.swbell.net/rlf47/index.htm