Apr 15, 2002 ... Modified Vehicle Wiring System. • Disconnecting the Battery. Electrical
Documentation. A high quality electrical system begins with an Electrical ...
ELECTRICAL/KEY-OFF CURRENT DRAIN APPENDIX Introduction A carefully designed Electrical Documentation Plan is a vital part of the Ford Truck Quality Program because of its impact on: 1. Overall Customer Satisfaction 2. Vehicle Safety and Reliability This Appendix discusses: • Electrical Documentation • Vehicle Electrical Layout/Electrical Documentation Worksheet • Owner's Information • Electrical Requirements/Guidelines • Modified Vehicle Wiring System • Disconnecting the Battery Electrical Documentation A high quality electrical system begins with an Electrical Documentation Plan. This appendix offers some suggestions, which converters can use to implement an Electrical Documentation Plan which works well in their unique operation. To begin any planning effort, three basic elements must be considered: 1. A Careful Plan Design considers the best way to perform a job considering all interrelated tasks. 2. A Consistent Production Effort follows a written plan knowing that any deviation could cause poor quality. 3. Assembly With a View to the Future "designs in" all processes and product features that will make maintenance and repair easier when they're required. When these basic manufacturing elements are applied, the results are: • Reduced time and money spent for extensive troubleshooting • Customer friendly routine service items such as fuses • More efficient use of parts, material and labor • Service personnel user friendliness • Electrical Documentation Plan for review by Ford's Engineering Assessment Teams
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Vehicle Electrical Layout/Electrical Documentation Worksheet The Vehicle Electrical Layout/Electrical Documentation Worksheet (attachments I and II) is an example of an easy-to-understand Electrical Documentation Plan. A blank worksheet and layout sheet is also provided (see attachments III and IV) so that an Electrical Documentation Plan can be designed for your unique operation. • • • • • • • • • •
The Electrical Documentation Worksheet provides the following information: The circuit number. The circuit items for each circuit. The item number referenced to the vehicle electrical layout. The quantity of each circuit item. The wire gauge and color for each circuit item. The power source and its location in the vehicle. The calculated amperage draw for each circuit item. The actual amperage draw for each circuit item. The fuse size and location for each circuit.
Owner's Information The Electrical Documentation Worksheet and Vehicle Electrical Layout should be part of the Electrical Information provided to the customer. This information should also include the size, location and description of all added fuses (See Attachment V, Fuse Panel Information). Additional Guidelines Routings All wiring should be routed neatly to avoid any visual issues. All wiring should be secured adequately to avoid any functional issues. Wiring should not be routed through wheel well areas where it may be damaged by tire or road debris. Wiring should not be routed over the exhaust system. All wiring should be protected from fastener damage during the build process and from abrasion from any unfriendly surface in dynamic conditions. Wiring which is located in the passenger compartment should be routed away from high temperature areas (e.g., floorpan over catalytic converter). Rubber grommets should be used when routing wiring through any sharp edged hole. When routing wiring over, through or near any sharp edge or fabricated cut-out, rubber edged guards and/or convoluted tubing should be used.
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Disconnecting The Battery There are two things to remember when performing any work on the electrical system. Disconnect and isolate the negative battery cable to avoid power drain or damage to the circuitry. Disconnection of either battery cable will result in a temporary memory loss to the engine and transmission control modules. Module memory is restored after several miles of driving under varied conditions.
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BATTERY DRAIN / KEY-OFF LOADS Background Key-off load is defined as the current drain on the battery when the ignition key is in the off position. A study conducted by (SVE), Special Vehicle Engineering, on 34 conversion units from 12 manufacturers identified two causes for the higher warranty on modified vehicles. 1. During the modification/conversion process, electrical loads are placed on the battery by doors left open, radios playing, and starting the engine frequently to move the vehicle several feet at a time. During this process, the engine is never left running long enough to return the battery to a full state of charge; subsequently, the battery leaves the final stage manufacturer with a less than full state of charge. 2. Key-off loads on modified/converted vehicles ranged from 4 milliamps to 110 milliamps. Four vehicles were found to have key-off loads in excess of 40 milliamps; this included one vehicle with a vacuum cleaner system (that should have been wired to an ignition hot circuit) and another with a courtesy light that would not go out (shorted).
ACTION Key off battery loads for modified/converted vehicles are to be designed such that they do not exceed 24 milliamps for the 72 amp-hr battery or 28 milliamps for the 84 amp-hr battery. Note: the 84 amp-hr battery is available only with the auxiliary battery. Please ensure the battery is at a full state of-charge (i.e., the green eye of the battery is showing) prior to shipment of the completed conversion van modified vehicle to the dealer. The battery must be disconnected when the vehicle is stored for more than 30 days; before, after, or during the build process. Included in this bulletin are two procedures for measuring key-off loads.
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SUMMARY 1. It is the responsibility of all final stage manufacturers to ensure key-off loads do not exceed 24 milliamps for the 72 amp-hr battery or 28 milliamps for the 84 amp-hr battery. 2 The green eye of the battery must be showing prior to shipment. To measure battery drain, see illustrations below. METHOD 1: using ammeter Note: This method requires an ammeter capable of reading 0.010 amps. 1. Turn the ignition off and make sure there are no electrical loads on. After determining the engine compartment lamp is turning off properly, remove the engine compartment lamp miniature bulb. 2. Check the battery voltage; if the voltage is less than 11.5 volts, charge the battery to above 11.5 volts. 3. Disconnect the battery ground cable. 4. Place an ammeter capable of reading milliamps, in series between the battery ground cable and the negative terminal of the battery. See Figure 1. Current drain should not exceed as specified. Note: When the vehicle is equipped with an alarm system, using a jumper wire to temporarily maintain continuity between the battery and the battery cable will stop the alarm from sounding prior to placing the meter in the circuit.
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METHOD 2: using voltmeter Note: this test requires a digital voltmeter with a low voltage scale capable of reading 0.01 volt. 1. Repeat steps 1, 2, and 3 above. 2. Connect the shunt assembly as shown in Figure 2.
FIGURE 2 FIGURE 1
Connect the voltmeter leads to shunt as shown. With this size shunt (50 mV =50 amp.) and voltmeter, a direct current drain measurement can be made.
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