How to find an electrical drain
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1. Remove the battery ground (negative) cable from the battery negative terminal. (Vehicles with dual batteries, isolate main battery by disconnecting negative battery cable from secondary battery while performing parasitic draw test). | 1. Remove the battery ground (negative) cable from the battery negative terminal. (Vehicles with dual batteries, isolate main battery by disconnecting negative battery cable from secondary battery while performing parasitic draw test). | ||
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2. Install the J 38758 male end to the battery negative terminal. | 2. Install the J 38758 male end to the battery negative terminal. | ||
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3. Turn the J 38758 knob to the "OFF" position. | 3. Turn the J 38758 knob to the "OFF" position. | ||
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4. Install the battery ground (negative) cable to the female end of the J 38758. | 4. Install the battery ground (negative) cable to the female end of the J 38758. | ||
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5. Turn the J 38758 knob to the "ON" position. | 5. Turn the J 38758 knob to the "ON" position. | ||
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6. Road test the vehicle and activate all of the accessories (radio, A/C, etc.). | 6. Road test the vehicle and activate all of the accessories (radio, A/C, etc.). | ||
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7. Stop the vehicle. Turn the ignition switch to the "OFF" position and remove the ignition key. | 7. Stop the vehicle. Turn the ignition switch to the "OFF" position and remove the ignition key. | ||
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8. SET the J 39200 to the 10 ampere scale and connect it to the terminals on test switch tool. | 8. SET the J 39200 to the 10 ampere scale and connect it to the terminals on test switch tool. | ||
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9. Turn the J 38758 knob to the "OFF" position to allow the current to flow through the J 39200. | 9. Turn the J 38758 knob to the "OFF" position to allow the current to flow through the J 39200. | ||
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10. Wait at least 20 minutes. Check and record the current reading. If the current reading is at or below two amperes, turn the J 38758 knob to the "ON" position (to maintain continuity in the electrical system) and switch the J 39200 down to the two ampere scale for a more accurate reading when the J 38758 knob is turned "OFF" | 10. Wait at least 20 minutes. Check and record the current reading. If the current reading is at or below two amperes, turn the J 38758 knob to the "ON" position (to maintain continuity in the electrical system) and switch the J 39200 down to the two ampere scale for a more accurate reading when the J 38758 knob is turned "OFF" | ||
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| − | + | 11. Note the reserve capacity rating for the vehicle's battery. If the battery does not specify the reserve capacity, 30 milliamps can be used for a maximum parasitic draw on most vehicles. However some vehicles can have up to 50 milliamp parasitic draw. | |
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| − | + | o Divide the reserve capacity number by four. | |
| + | o Compare this number to the ampere reading taken in step ten. | ||
| + | o The parasitic current drain should not exceed this number. | ||
| + | o Example: If the battery has a reserve capacity rating of 100 minutes , the current drain should not exceed 25 milliamps. | ||
12. If the vehicle has an acceptable amount of current drain and the vehicle battery was weak or failed a load test, check the charging system for proper operation, refer to Charging System . | 12. If the vehicle has an acceptable amount of current drain and the vehicle battery was weak or failed a load test, check the charging system for proper operation, refer to Charging System . | ||
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13. If the vehicle has an unacceptable amount of current drain, remove each fuse one at a time until the current drain is at an acceptable level (this will indicate which circuit is causing the drain). Then diagnose exactly which part of the suspect circuit is causing the drain. In some rare cases, a "non-fused" circuit or component, such as a generator, may be the cause of excessive current drain. NOTE : Always turn the parasitic draw test switch knob to the "ON" position before removing each fuse to maintain continuity in the electrical system and to avoid damaging the ammeter due to accidental overloading (I.E. opening door to change fuse etc.). IMPORTANT : | 13. If the vehicle has an unacceptable amount of current drain, remove each fuse one at a time until the current drain is at an acceptable level (this will indicate which circuit is causing the drain). Then diagnose exactly which part of the suspect circuit is causing the drain. In some rare cases, a "non-fused" circuit or component, such as a generator, may be the cause of excessive current drain. NOTE : Always turn the parasitic draw test switch knob to the "ON" position before removing each fuse to maintain continuity in the electrical system and to avoid damaging the ammeter due to accidental overloading (I.E. opening door to change fuse etc.). IMPORTANT : | ||
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