Coolant fan override switch

[David Brady]

Leroy,

From a circuit standpoint, I think you're looking for an Open Collector
Output on each of the signals: a/c, override switch, and alarmstat. All
three would then be tied together and pulled up with a power source
and a resistor. This signal could then be fed into the bypass switch.

When all signals are off, the pull up resistor supplies power to the bypass
enabling the piston and the slow fan speed. When one or more of the input
signals drives it's Open Collector output to ground, the pull up
resistor will
be driven to ground and in turn the input to the bypass switch will be
ground
resulting in the release of the piston and a high fan speed.

If the power source goes away, then the input to the bypass switch loses
it's
voltage and the bypass defaults to high fans speed.

This can easily be implemented with transistors, relays are another story...

David Brady
'02 LXi, Smokey
NC

Leroy Eckert wrote:
> Ok, thanks. Now all I have to figure out is how any one of the three
components disables the other two when in high mode. Somehow, the a/c and
override switch must be tied to the Alarmstat NC sensor . I just haven't figured
that one out. I want to make an electrical drawing of my system. If I figure it
out, I'll post it.
>
> Thanks,
>
> Leroy Eckert
> 1990 WB-40"Smoke N Mirrors"
> Niceville, FL
>
>
>
> ----- Original Message -----
> From: g_man1146
> To: WanderlodgeForum@yahoogroups.com
> Sent: Tuesday, February 20, 2007 9:11 AM
> Subject: [WanderlodgeForum] Re: Coolant fan override switch
>
>
> Leroy,
> You are correct; the fan bypass defaults to closed, thereby forcing
> all of the pump output through the fan motor. Cool temperatures, air
> conditioner "ON" or "Fan Override" switch "ON" all hold the bypass
> valve open allowing oil to flow around the fan motor. When I was
> attempting to diagnose what turned out to be a defective pump, BB
> sent me a diagram and test procedure to follow. They said the LXi
> shared the same system as the "LTC" commercial coach.
>
> Rich D. '99LXi43' CT
>
> --- In WanderlodgeForum@yahoogroups.com, "Leroy Eckert"
> wrote:
> >
> > Rich: I have a question on the bypass valve if you know. I do not
> have a drawing of the valve.
> >
> > As I understand the system, the fan is normally in idle(bypass)
> mode until one of three things happen. The alarmstat activates high
> mode based on water temperature, the fan override(manually by humans
> or grandkids) activates high mode or the chassis a/c on switch
> activates high mode.
> > Does the fan bypass valve default to fan high mode? . That would
> make sense otherwise the system would overheat with valve or
> electrical failure. If so, one could conclude that the piston in the
> valve is actuated by continuous power in the bypass position and the
> fan override, a/c switch and alarmstat cuts power off to it and it is
> spring loaded to full fan mode.
> >
> > If you know. Thanks. Trying to learn more here.
> >
> >
> > Leroy Eckert
> > 1990 WB-40"Smoke N Mirrors"
> > Niceville,FL
> >
> >
> >
> >
> >
> >
> > ----- Original Message -----
> > From: Leroy Eckert
> > To: WanderlodgeForum@yahoogroups.com
> > Sent: Monday, February 19, 2007 9:35 PM
> > Subject: Re: [WanderlodgeForum] Re: Coolant fan override switch
> >
> >
> > That was to Greg, but I think we are all speaking of the same
> thing, just a different component in the system with a bypass. The
> fan control valve has a bypass as does the Parker filter. The
> override sends a message so to speak to the valve to stop the bypass
> and get into high mode. So does the chassis a/c on switch. If the
> valve is bad, the fan will not spool up.
> >
> > Leroy Eckert
> > 1990 WB-40"smoke N Mirrors"
> > Niceville, FL
> >
> > ----- Original Message -----
> > From: g_man1146
> > To: WanderlodgeForum@yahoogroups.com
> > Sent: Monday, February 19, 2007 9:08 PM
> > Subject: [WanderlodgeForum] Re: Coolant fan override switch
> >
> > Gregory,
> >
> > On the later model Series 60's the fan bypass valve diverts
> > hydraulic oil around the fan motor to allow the fan to run at a
> > lower speed by sending the oil back without going through the
> > fan "motor". If the bypass valve fails, you get full RPM of the
> fan
> > as all of the oil is directed to the fan motor. This has nothing
> to
> > do with a filter bypass. The bypass valve can also be tested by
> > plugging the return line that goes to the bypass valve thus
> forcing
> > all oil through the fan motor.
> >
> > Rich D. '99LXi43' CT
> >
> > --- In WanderlodgeForum@yahoogroups.com, "Leroy Eckert"
> > wrote:
> > >
> > > Yes.
> > >
> > > Leroy Eckert
> > > 1990 WB-40"Smoke N Mirrors"
> > > Nicevile, FL
> > >
> > >
> > > ----- Original Message -----
> > > From: Gregory OConnor
> > > To: WanderlodgeForum@yahoogroups.com
> > > Sent: Monday, February 19, 2007 8:02 PM
> > > Subject: [WanderlodgeForum] Re: Coolant fan override switch
> > >
> > >
> > > David, Bypass and override are two independent features. I
> > believe
> > > bypass is a safety feature for a clogged hydro oil filter.
> > Bypass is
> > > not triggered by the override dash switch
> > > GregoryO'Connor
> > > 94ptRomolandCa
> > >
> > > --- In WanderlodgeForum@yahoogroups.com, David Brady
> > > wrote:
> > > >
> > > > Hi Rich,
> > > >
> > > > Thanks for the help. When I return to the bus I'll try your
> > test.
> > > > I guess if the fan speed increases, then the problem is
> between
> > > > the dash switch and the "bypass valve". Alas, no wiring
> > schematics..
> > > > I'll let you know what happens.
> > > >
> > > >
> > > > David B
> > > > '02 LXi, Smokey
> > > > NC
> > > >
> > > > g_man1146 wrote:
> > > > > Hi David,
> > > > >
> > > > > AS others have stated, a fan over-ride failure should fault
> > to
> > > high
> > > > > speed. If you are not getting high fan speed with the air
> > > conditioner
> > > > > on or with the switch set to "over-ride" locate (assuming
> > Detroit
> > > S60)
> > > > > a connector plug at the rear of the engine compartment
> > (closest
> > > to rear
> > > > > bumper) on the fan side. You should see a hydraulic hose
> > from the
> > > fan
> > > > > motor to this block (bypass valve) and wires coming from
> it.
> > If
> > > you
> > > > > disconnect the connector plug on these wires, the fan
> should
> > come
> > > up to
> > > > > full RPM. (ROAR) If it increases but not fully, the problem
> > may
> > > lie
> > > > > with the hydraulic pump which is attached to the PTO on the
> > curb
> > > side
> > > > > of the Allison or with the hydraulic bypass valve. BB makes
> > > changes all
> > > > > the time and my coach (3 years older) may not be set up the
> > same.
> > > If
> > > > > you are not overheating on long hills everything may be
> > normal. I
> > > > > experienced an overheating situation only in extreme
> > situations
> > > and
> > > > > determined the problem to be a faulty hydraulic pump
> > supplied as
> > > part
> > > > > of the PTO recall from BB. The pump did not have sufficient
> > > capacity to
> > > > > run the fan at full speed. They supplied a new pump and
> > labor to
> > > > > install. The fan motor is actually rated at about 40 HP at
> > full
> > > > > capacity. No wonder it is designed to cut back when not
> > needed!
> > > > >
> > > > > Rich D. '99LXi43' CT
> > > > >
> > > > > --- In WanderlodgeForum@yahoogroups.com, David Brady
> >
> > > wrote:
> > > > >
> > > > >> Folks,
> > > > >>
> > > > >> On my '02 LXi, with the engine at idle, the fan seems to
> > rotate
> > > > >> at 400 rpm or so (give or take, lol), when I enable the
> > override
> > > > >> switch there doesn't seem to be any change in fan speed.
> > Should
> > > > >> there be? or are there other parameters at work hear;
> i.e.,
> > > engine
> > > > >> temp, etc. What are the common failure modes of the fan
> > override?
> > > > >>
> > > > >> Thanks,
> > > > >> David Brady
> > > > >> '02 LXi, Smokey
> > > > >> NC
> > > > >>
> > > > >>
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > Yahoo! Groups Links
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > > [Non-text portions of this message have been removed]
> > > >
> > >
> > >
> > >
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>