Air throttle and related systems

[Ralph L. Fullenwider]

Hi Bill:

The FC's have something the PT's don't, and that is 2 large solenoids to
the left of the Bendix control unit.

One day, I had the panel under the coach open, tracing a problem I was
having and nothing I did seemed to make any difference at all. Out of
frustration, more or less, I turned the bolts that held the solenoids to
the back of the panel and all of a sudden everything started working to
beat the band.

What I found was, rust had become an insulator and the solenoids were not
making a good ground so the system just would not work as advertised.
Interesting. Anyway, I pulled the bolts, wire brushed everything and re
installed with new stainless bolts, and what I thought was low voltage went
away. Just a thought.

I also cleaned up the valve, which was sticky and devised an inline gauge
to check the air pressures going through each point. Over kill I know, but
it sure took some of the do I or don't I stuff out of the equation. Then I
added a relay so the on/off switch pulled the coil of the relay and through
the contacts of the relay I went straight from the batteries to the power
input of the Bendix. That was a good mod.

Truth be known, Charolette had some "honey do's" for me and I was avoiding
them so I took the time to make the gauge set up for those checks,

Safe travels,

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

At 05:14 PM 11/27/2005 +0000, you wrote:


>Ralph,
>
>Thanks for the info. I was unaware of the minimun
>idle air pressure needed, I am hoping my idle problem was
>not enough air pressure, when engaging the idle controlls.
>It could also be the pressure reducing valve or the check valve.
>
>This is a minor issue for me, not high on the list.
>The electronic module seems to work fine at highway
>cruise control speeds.
>
>
>Bill 88 Fc
>
>
> > 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.
> >
>