Garnet SeeLeveL Special 809-DM User Manual page 10

2. The PTO status is normally detected by an air pressure switch
connected to the PTO pneumatic control line. This switch may
already be present on the truck for other purposes, such as
an indicator light, or it may need to be installed as part of the
gauge installation.
3. Normally the PTO switch will have one side connected to
ground, and the other side connected to the PTO input on the
gauge. If one side of the PTO switch is connected to 12 volts
instead of ground, then an external load such as an indicator
light must be used. See the appropriate wiring diagram for
details.
4. There are two parameters that must be set in order for the
PTO sensing to work properly, the PTO pull-up resistor and
the PTO polarity.
5. The PTO pull-up resistor must be turned on if the air pressure
switch has one side connected to ground and the other side
is not connected to a light bulb or any other load. If there is
a light to indicate PTO status from the switch, then the pull-
up can be turned off. To set the pull-up, connect the 809DM
Serial Port Tester to the connectors in the base of the gauge
display and turn it on. Press the PULLUP PTO I/P button and
then ENTER to check the current status of the pull-up. To
change it, press the same button and then either 0 or 1 (as
shown on the Tester screen) to configure the pull-up.
6. The PTO polarity must be set to match the type of switch
used to detect the air pressure. If the switch has one side
connected to ground and closes when the PTO is engaged,
then the input will be grounded when the PTO is engaged
(e=0). Conversely, if the switch opens during engagement,
then the input will be grounded when the PTO is disengaged
(e=1). If one side of the switch is connected to 12 volts, then
this will reverse the polarity of the switch.
7. To check the polarity, connect the 809DM Serial Port Tester to
the connectors in the base of the gauge display and turn it on.
Verify that the PTO is either engaged or disengaged. Then
press the PTO STATUS button on the Tester and then ENTER,
the Tester screen will then show what the gauge thinks is the
PTO status. If this is incorrect, then press the SHIFT and PTO
I/P POLAR buttons at the same time on the Tester, then ENTER
to show the current polarity setting. To change the setting,
press the SHIFT and PTO I/P POLAR buttons again followed
by either 0 or 1 as required. Then press ENTER to properly
configure the polarity.
8. Verify that the gauge now is properly sensing the PTO polarity
using the PTO STATUS button on the Tester.
Page 10 809-DM Manual