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LOFA MC704 and MC704 G4 Operation and Troubleshooting
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design uses high-power semiconductors instead of outdated electromechanical relays to ensure reliable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.
463-3000-02 Rev C.2 - 15-April -2008
1
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Summary of Contents for Lofa MC704
- Page 1 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.
- Page 2 LOFA MC704 and MC704 G4 Operation and Troubleshooting 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.
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Page 3: Operation
LOFA MC704 and MC704 G4 Operation and Troubleshooting 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. - Page 4 LOFA MC704 and MC704 G4 Operation and Troubleshooting 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.).
- Page 5 LOFA MC704 and MC704 G4 Operation and Troubleshooting sender/switch combinations, swapping the WK or W and G terminal 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.
- Page 6 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.
- Page 7 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.
- Page 8 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.
- Page 9 LOFA MC704 and MC704 G4 Operation and Troubleshooting 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.
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Page 10: General Troubleshooting
LOFA MC704 and MC704 G4 Operation and Troubleshooting 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) - Page 11 LOFA MC704 and MC704 G4 Operation and Troubleshooting Fuel Run/Stop Solenoid Troubleshooting Engine does not stop immediately Possible Cause Possible Remedy Back feed from motor (i.e., Add relay or blocking diode cooling fan) Sticking solenoid linkage Repair or replace solenoid linkage...
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Page 12: Control System Troubleshooting
LOFA MC704 and MC704 G4 Operation and Troubleshooting Control System Troubleshooting Control system does not perform self test Possible Cause Possible Remedy Tripped overcurrent protection Correct fault, replace or reset overcurrent protection Faulty connection to battery Correct battery connections (see Battery Circuit Requirements above) - Page 13 LOFA MC704 and MC704 G4 Operation and Troubleshooting " Power Box Option The Power Box is a solid state, high current control system for mechanically governed, industrial diesel engines. In addition to allowing extended harnesses, the Power Box provides 3-wire fuel run/stop solenoid control to protect the pull coil from overheating.
- Page 14 LOFA MC704 and MC704 G4 Operation and Troubleshooting 463-3000-02 Rev C.2 -15-April-2008...
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