Service Manual

Part Numbers
114825, 115207, 79-2130
Purpose
The circuit board drives the dash indictor lights. It monitors the status of
switches and does not affect normal operation.
How It Works
The light circuit module (printed circuit board) uses an array of resistor and
diodes to get each of the light emitting diodes (LEDs) to light under the
right conditions. While the board itself is complex, understanding the
conditions needed to light the LEDs is not difficult. It is just a matter of
either grounding or applying 12 volts D.C. to the appropriate terminals on
the edge of the card.
Testing
Use the circuit diagrams in the back half of this book to troubleshoot the
module.
Important! All tractor electrical systems will operate normally with the light
circuit module completely disconnected.
Part Numbers
71-6380, NN10444
Purpose
The ignition control opens the primary circuit as the magnet passes by to
induce spark at the proper time.
How It Works
This engine is equipped with an electronic battery ignition system. Both
spark plugs fire simultaneously, thus the need for a distributor is
eliminated. The electronic ignition module is located on the engine gear
cover behind the flywheel. The module receives a timing signal from
magnets within the trigger ring which rotates with the engine crankshaft
(Figure 1). If the electronic ignition is suspected of malfunctioning, proceed
as follows.
Testing
1. Check all electrical connections to be sure they are clean and tight. If
all connections are good and wiring is intact, go to Step 2.
Warning: The electronic ignition will deliver full voltage to the spark
plugs even when rotated by hand. Care should be taken to avoid an
electrical shock.
Warning: Failure to remove spark plugs before turning the engine
over may result in engine starting and may cause severe personal
injury.
Warning: Failure to ground spark tester away from the spark plug
hole may result in ignition of cylinder gases and may cause severe
personal injury.
Module
Trigger
(Onan)
Trigger
Ring
Ignition
Module
Figure 1
Module
Light Circuit
Glossary
GLOSSARY
Demystification Guide 3-13