HWH 725 SERIES Service Manual Download Page 13

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MI91.327F

01NOV11

PART 5. SECTION A.2. CONTINUED

If voltage at the touch panel is good, unplug the 32 pin harness connector at the I/O module.
Check and record the voltage between pin D1 of the 32 pin harness connector and the brass
ground stud on the top of the I/O module. Plug the 32 pin connector back in. Disconnect the
#9000 park brake wire from the park brake switch connection. Make sure there is no ground
on the #9000 park brake wire. Check the voltage between the #9000 wire, pin D8 of the 32 pin

Strip some insulation from the wire close to the connector. Make sure to repair the wire with
some type of sealant when the test is finished. The voltage should be within less than 1 volt
of the voltage you recorded on pin D1 of the harness connector. If there is a difference in the
voltage greater than 1 volt, the I/O module needs to be replaced. If the voltage is good, the
problem is the I/O module or touch panel. Replace the touch panel first. If the problem
remains, reinstall the original touch panel and replace the I/O module.
SEE: MP84.3170

PART 6. FOR VEHICLES EQUIPPED WITH AIR SUSPENSION

The two types of suspension air dump, pilot air dump or HWH air dump valves, are explained in the
SYSTEM OPERATION and GLOSSARY sections of this manual. The ignition must be in the "ON" or
"ACC" position and the park brake must be set for the air dump system to function. The vehicle
should be at ride height with all air bags full of air when checking air dump.

PILOT AIR DUMP: The air should start to dump when the "dump" button is pushed and

continue to dump when the "dump" button is released. If the ignition is on and the "store"
button is pushed or the park brake is released, the vehicle should return to ride height if
there is ample air in the suspension air tanks.

If both link lights are flashing, the next step is checking voltage.
check voltage between the white and red wire in the 5 pin MTA connector on the back of

voltage to the I/O

module should be checked. Ign./Acc. voltage to the I/O module is on pin D1 in the 32 pin
connector at the I/O module. Ground for the I/O module (and touch panel) is a 14 gauge
wire coming out of the top of the I/O module, not the brass ground stud on the module. If
voltage to the module is low, check all ground connections and the voltage source. If voltage
to the module is good but there is low voltage coming from the module to the touch panel, make
sure all connections for the red 6800 wire on pin B1 and white 6230 wire on pin B3 are good. If

when pushing an up arrow with the park brake released,

set the park brake and push any UP arrow. If the pump runs with the park brake set, the
problem is the touch panel. If the pump does not run with the park brake set, the problem
is the touch panel, the I/O module, a communication problem or a voltage issue.

Check the link light on the back of the touch panel and on the I/O module.
Both lights should be flashing. If either light is off or on steady, go to PART 1,
"TOUCH PANEL TO I/O MODULE COMMUNICATION CHECK".

If there is less than 10.5 volts at the touch panel,

Use a voltmeter to

SEE: MP84.3334 and MP84.3170

MANUAL OPERATION

725 TROUBLE SHOOTING STEPS

MANUAL SYSTEM OPERATION

IF THE PUMP DOES NOT RUN

MP84.3334

PIN 4

MP84.3170

PIN 1

LINK LIGHT