Lofa MC704 Operating instructions

LOFA MC704 and MC704 G4 Operation and Troubleshooting
463-3000-02 Rev C.2-15-April -20081
Introduction
This document provides general information on LOFA Industries MC704 control systems operation and
troubleshooting. MC704 control systems are a very flexible platform for diesel engine control, monitoring,
and protection, featuring LOFA’s powerful First Fault Diagnostics (FFD). After pinpointing the initial failure,
FFD stores it in memory and alerts the end user via a single bright LED. FFD monitors battery charge, low oil
pressure, high temperature and one additional contact closure input. The microprocessor-based solid-state
design uses high-power semiconductors instead of outdated electromechanical relays to ensure reliable
high-current switching.
The MC704 panels are offered in two versions. The MC704HP has a built-in tamperproof LED hourmeter
while the reduced cost MC704LCP eliminates the hourmeter. The G4 variant includes up to four 2 inch
gauges. All panel versions can be factory configured with specific preheat & afterglow requirements. If
preheat is not required, this output can function as an alarm.
All standard panels include feature a 12 inch wiring harness terminating into a sealed weather proof plug.
This robust universal wiring connection performs well in harsh environments and allows interchanging a
number of different panels and harnesses. This design allows for simplified installation as well as a flexible
means to incorporate custom plug-and-play engine wiring harnesses and standard harness extension
Note
The engine harness is not included with the panel.
A number of standard engine harnesses are available or
LOFA can develop a custom harness for you exact needs.
Generic harnesses in various lengths are available for field customization.
Warning
When replacement parts are required, LOFA Industries recommends using replacement parts
supplied by LOFA or parts with equivalent specifications.
Failure to heed this warning can lead to premature failure,
product damage, personal injury or death.

LOFA MC704 and MC704 G4 Operation and Troubleshooting
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Important Safety Information
The warnings in this publication are not all inclusive.
LOFA Industries cannot anticipate every potential hazard.
Appropriate safety rules and precautions should be followed with any
tool, work method or operating procedure.
Improper procedures, tools and materials may cause
damage or make the equipment unsafe to operate.
Only persons with appropriate training, skills and tools
should perform these functions.
Improper operation, maintenance or repair of this product can be
dangerous and may result in injury or death.
Do not operate or perform any maintenance or repair on this product until all operation,
maintenance and repair information is read and understood.
The information, specifications, and illustrations in this publication are based on information
available at the time of publication.
All items are subject to change at any time without notice.

LOFA MC704 and MC704 G4 Operation and Troubleshooting
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Operation
Turning the control system key to the run position starts a self-test which causes all LEDs to flash three times,
activates the alarm output (if preheat is not used) for one second and enables the fuel run/stop solenoid
output. After self-test, the LEDs indicate the state of the inputs they monitor. The normal indications are
battery charge and oil pressure on most applications. If these LEDs are not illuminated at this time it may
indicate the inputs are not properly connected.
The Preheat/OK LED begins to blink when the key switch is turned to the run position if automatic preheat is
configured (See Preheat Options). Preheat time varies from application to application. After waiting for the
Preheat/OK LED to become solid, the engine is cranked by turning and holding the key switch in the start
position until the engine starts. The key switch is spring loaded to return automatically to the run position
when released.
Note
The key switch is equipped with a mechanical start locking device.
An attempt to re-crank the engine can only be made by turning the key switch
to the off position to reset the start locking mechanism.
If the engine is not started within 30 seconds of turning on the system, the fuel run/stop solenoid output is
turned off to prevent battery discharge when the key switch is left in the run position. The fuel run/stop
solenoid output is turned off after 30 seconds even if preheating. As soon as the key switch is turned to the
start position the solenoid output is enabled. The afterglow cycle begins when the key switch returns to the
run position.
Note
If conditions do not warrant preheat, the engine may be started by turning the key to the start
position without waiting for the preheat time to expire.
Control system instrument power, including the hourmeter and voltmeter, is provided by the fuel run/stop
solenoid output. If the instruments do not power up when the key is turned to the run position, this indicates
a problem with the solenoid circuit (see Troubleshooting).
After the engine starts, the control system electronics ignore all shutdown conditions for the first 10 seconds.
This delay eliminates the requirement to hold a by-pass override button during starting and allows the system
conditions such as oil pressure to normalize. The 10 second timer starts when the key switch returns to the
run position.
Note
Starter input is required for correct system operation. If the starter motor input is not activated
(connected to battery positive) and the engine is started through another means (i.e. air
starter) the engine will shutdown 30 seconds after the key switch is turned to the run position.
To prevent unintentional engine shutdowns caused by intermittent conditions (i.e., pressure spikes, coolant
movement) the control system requires a constant 1/3 second fault input to cause engine shutdown.
Warning
When used in combination with mechanical float type switches
engine vibrations may prevent constant contact closure.

LOFA MC704 and MC704 G4 Operation and Troubleshooting
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Preheat Options
Preheat Output
Preheat is a 3A positve output for control of an external power relay with predetermined preheat and
afterglow times. A relay should be selected with appropriate amperage capacity for the installed cold starting
aid (glowplug, intake air heater, etc.). Applications using multiple cold starting aids may require multiple
relays.
Note
Consult engine documentation when selecting cold starting aid,
power relay and heating specifications.
Indicators
Battery LED (Red)
A solidly illuminated Battery LED indicates a battery charge failure. A battery charge failure may be caused
by a faulty alternator, broken drive belt or the alternator not excited. A battery voltage reading of
approximately 14 volts on a 12 volt system (28 volts on a 24 volt system) while the engine is running
indicates the battery is charging properly. Irregular blinking of the Battery LED may indicate a failing charge
circuit. The system can be configured for battery charge failure to indicate only.
Oil Pressure LED (Red)
A solidly illuminated Oil Pressure LED indicates low oil pressure failure. The control system typically senses
low oil pressure from a ground contact switch on the engine. When a sender/switch combination is used on
the engine, the marking WK generally indicates the switch terminal. This input typically expects a normally
closed switch (ground contact when oil pressure is low). A defective switch or shorting the shutdown input to
ground can cause low pressure fault indication. Additionally, when using sender/switch combinations,
swapping the WK and Gterminal can cause unintended shutdowns. The system can be configured for oil
pressure failure to indicate only.
Warning
Low oil pressure is not an indication of low oil level.
For best possible protection LOFA recommends using
our solid-state oil level shutdown switch.
Note
Most shutdown switches are grounded through the switch body.
Do not use insulating sealant (i.e. Teflon tape) when installing switches.
Temperature LED (Red)
A solidly illuminated Temperature LED indicates high engine temperature failure. The control system typically
senses high temperature from a ground contact switch on the engine. When a sender/switch combination is
used on the engine, the marking WK or Wgenerally indicates the switch terminal. This input typically expects
a normally open switch (ground contact when engine temperature is too high). A defective switch or shorting
the shutdown input to ground can cause over temperature fault indication. Additionally, when using

LOFA MC704 and MC704 G4 Operation and Troubleshooting
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sender/switch combinations, swapping the WK or Wand Gterminal can cause unintended shutdowns. The
system can be configured for temperature failure to indicate only.
Warning
If the temperature switch is not in contact with coolant due to
coolant loss the engine is not protected from overheating.
For best possible protection, LOFA recommends using
our solid-state coolant level shutdown switch.
Note
Most shutdown switches are grounded through the switch body.
Do not use insulating sealant (i.e. Teflon tape) when installing switches.
Some thermostat housings are composites and do not provide ground for the switch.
AUX LED (Red)
A solidly illuminated AUX LED indicates an auxiliary failure (i.e., coolant level, oil level, belt breakage,
hydraulic pressure, etc.). The control system typically senses failure using a ground contact switch. Auxiliary
inputs are equipment specific and determined by the equipment manufacturer. A defective switch or shorting
the shutdown input to ground can cause fault indications. The system can be configured for auxiliary failure
to indicate only.
Preheat/OK LED (Green)
A blinking green Preheat/OK LED is the system preheat indication. When the LED changes to solid the
preheat period is complete and the engine may be cranked. The LED changes to solid illumination when the
engine starts. There is no indication of afterglow.

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Harness
Sealed Connectors
The provided sealed weather proof plug includes a grey locking device which must be released to separate
the connectors. Press the tab on the connector housing to release the connectors.
Warning
LOFA does not recommend using dielectric grease or sealant with sealed connectors.
These chemicals may cause seal damage and allow water entry.
Use LOFA provided cavity plugs to seal the connector if wires are removed.
Unsealed Connectors
For unsealed connectors exposed to the elements, LOFA recommends using dielectric grease to protect
contacts.
Warning
LOFA does not recommend using sealant with unsealed connectors.
Sealant traps moisture in the connector and encourages corosion.
Harness Routing
The minimum routing of radius of the wiring harnesses should be at least two times the diameter of the
wiring harness. Bends should be avoided within 1 inch (25 mm) of any connector in order to avoid seal
distortion allowing moisture to enter the connector.
Note
For harness length in excess of 10 ft a relay must be added to the start solenoid circuit.
LOFA offers starter relay kits for mounting near the engine.

LOFA MC704 and MC704 G4 Operation and Troubleshooting
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Battery Circuit Requirements
Battery Positive Connection
The electronic control system operates on either a 12 VDC or 24 VDC electrical systems. The unswitched
battery positive connection to the control system is made at the weather proof connector. The control system
provides switched positive battery
Protection for the unswitched battery positive circuit is dependent on specific equipment configuration. The
overload protection should not exceed 125% of the sum of all output currents plus 5 Amps for the control
system. Powering the control system through dedicated circuits with appropriate overload protection reduces
the possibility of system damage.
Circuit breakers are preferred over in-line fuses for circuit protection. Over current protection devices should
ideally be located in a central location. If automatic reset circuit breakers are used, consideration of the
environment of the breaker is critical and may affect the trip point. The trip point of some circuit breakers
can be significantly reduced below the rated trip point if the circuit breaker is exposed to high temperatures.
Warning
Disconnecting the battery while the engine is running
may damage electrical components.
When using a battery disconnect switch, LOFA recommends using a
2 pole switch to disconnect both the battery and alternator output.
Battery Negative Connection (Grounding)
Warning
Improper grounding can cause electrical noise, unreliable operation and may damage the
control system or other components. All ground connections must be free from foreign
materials, including paint, which may interfere with proper grounding.
A reliable ground must be provided for the control system.
LOFA recommends the ground connection be made directly to the battery negative.
Grounding through frame members is not recommended.
All ground paths must be capable of carrying any likely fault currents.
Do not reverse the battery polarity. Attempting to crank the engine when the polarity of the
battery connections is reversed may damage the control system.
Note
A maximum of three ring terminals should be connected to a ground stud in order to ensure
integrity of the ground connection. The use of more than three terminals can cause the
connection to become loose.
Voltage Drop
If control system voltage drops below 6 volts for more than one tenth of a second, the control system may
reset causing the self test to reactivate and the engine to shutdown after 30 seconds. Resetting the control

LOFA MC704 and MC704 G4 Operation and Troubleshooting
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system is equivalent to quickly turning the key switch to off and back to run without starting the engine. Since
the control system did not sense a start signal, the fuel run/stop solenoid deactivates after 30 seconds.
Voltage drops can be caused by transients from external equipment, improper wire sizes, faulty wiring or
nearby lightning strikes. In the absence of a LOFA Power Box, relays may be needed for long wire runs.
Suppression of Voltage Transients (Spikes)
Warning
The installation of voltage transient suppression at the transient source is required.
LOFA follows SAE recommended electrical environment practices.
Inductive devices such as relays, solenoids and motors generate voltage transients and noise in electrical
circuits. Unsuppressed voltage transients can exceed SAE specifications and damage electronic controls.
I
Relays and solenoids with built-in voltage transient suppression diodes are recommended whenever possible.
Refer to the illustration for proper installation of diodes when built-in voltage transient suppression is not
available.
Locate inductive devices as far as possible from the components of the electronic control system. When
using electric motors it may also be necessary to add isolation relays to eliminate voltage transients, noise
and prevent back feed.
Note
LOFA harness assemblies typically include all required engine control suppression devices.
Added equipment will require additional protection.

LOFA MC704 and MC704 G4 Operation and Troubleshooting
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Welding on Equipment with Electronic Controls
Proper welding procedures are required to avoid damage to electronic controls, sensors, and associated
components. The component should be removed for welding if possible.
The following procedure must be followed if the component must be welded while installed on equipment
with electronic controls. This procedure will minimize the risk of component damage.
Warning
Do not ground the welder to electrical components such as the control ground or sensors.
Improper grounding can cause damage to electrical components
Clamp the ground cable from the welder to the component being welded. Place the clamp
as close as possible to the weld to reduce the possibility of damage.
1. Stop the engine. Turn the key switch to the OFF position.
2. Disconnect the negative battery cable from the battery.
3. Open any installed battery disconnect switch.
4. Unplug the control system if possible.
5. Connect the welding ground cable as close as possible to the area to be welded.
6. Protect the wiring harness from welding debris and spatter.
7. Use standard welding methods to weld the materials.

LOFA MC704 and MC704 G4 Operation and Troubleshooting
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General Troubleshooting
For additional information, refer to engine manufacturer troubleshooting guide.
No response from starter motor
Possible Cause Possible Remedy
No battery voltage to starter Verify wiring and battery connection (power and ground)
Battery discharged Charge or replace battery, verify alternator charging
Tripped overcurrent protection Correct fault, replace or reset overcurrent protection
No signal from control system No power to control system (see Control System Troubleshooting below)
Defective starter solenoid Replace starter solenoid
Defective starter motor Replace starter motor
Engine will crank but not start
Possible Cause Possible Remedy
Engine not getting fuel Check fuel level, filter, fuel pump, verify no air in fuel lines
Fuel run/stop solenoid not
engaged
See Fuel Solenoid Run/Stop Troubleshooting (below)
Tripped overcurrent protection Correct fault, replace or reset overcurrent protection
No preheat (cold condition) See Preheat Troubleshooting
Engine runs for 10 seconds and shuts down
Possible Cause Possible Remedy
Shutdown switch input active Verify shutdown source exists, correct condition or correct faulty circuit
Battery not charging Verify alternator charging (see Alternator not charging battery below)
Control board did not sense
start signal
Engine started through alternate method (i.e., manual air start, push start,
etc.)
Defective control system See Control Panel Troubleshooting (below)
Engine runs longer than 10 seconds and shuts down
Possible Cause Possible Remedy
Shutdown switch input active Correct engine fault, verify shutdown switch wiring
Circuit overload protection
tripped
Correct overload, keep control system from overheating
(over 185° F/85° C)
Voltage transients (spikes) Add suppressor diodes, protect from nearby lightening strikes, shield
induced spikes from other equipment, add electric motor control relay
Defective control system See Control System Troubleshooting (below)
Alternator not charging battery
Possible Cause Possible Remedy
Broken or slipping alternator
drive belt
Adjust or replace alternator drive belt
Alternator not excited Verify excitation circuit connected, replace faulty regulator, add additional
excitation resistor
Alternator output not
connected
Install charge wire
Alternator not grounded Clean or add ground connection
Alternator faulty Replace faulty alternator