Coolant fan override switch

[g_man1146]

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]
>