Battery - Parasitic Draw Test
91chevy07
Number: 91-213-6D
Section: 6D
Date: February 1991
Corporate Bulletin No.: 116401
Subject: NO START CONDITION, VEHICLE BATTERY DEAD DUE TO EXCESSIVE CURRENT DRAW
Model and Year: 1980-91 ALL PASSENGERS CARS AND TRUCKS
Vehicles produced between 1980 and 1991 may experience a no start condition due to a dead battery. Follow the service manual procedures to test the battery and charging system. If the battery and charging system are functioning normally, an unusual current draw may have discharged the battery, resulting in the no start. The following procedure has been developed using the parasitic draw test switch, tool J 38758.
Past service procedures do not address solid state failures that appear as intermittent after the battery has been disconnected and reconnected. Utilizing tool J 38758, allows the vehicle to be started, driven, and all electrical system items cycled, without interrupting electrical system continuity. The following procedure supersedes all past "Battery Electrical Drain Test Procedures."
PARASITIC CURRENT DRAIN PROCEDURE
Figure 1 - Parasitic Draw Test Switch: J-38758.:
Tools needed: - J 38758 Parasitic Draw Test Switch (Figure 1)
- Ammeter with at least 10 amp measurement cabilities
NOTICE: The parasitic draw test switch should never be turned to the "OFF" position with the engine running or damage could occur to the attached ammeter or the vehicle electrical system.
1. Remove battery cable from battery negative terminal.
2. Install the parasitic draw test switch male-end, to negative battery terminal.
3. Turn test switch knob to the "OFF" position.
4. Install negative battery cable to female end of the test switch tool.
5. Turn the test switch tool knob to the "ON" position.
6. Road test vehicle while activating all accessories (radio, A/C etc.).
7. Turn ignition switch to the "Locked" position and remove ignition key.
8. Set ammeter to the 10 amp scale and connect to terminals on test switch tool.
NOTICE: Make sure all electrical accessories have been turned "OFF" (I.E. interior lights, underhood lamp, trunk light, illuminated entry, etc.) before turning the test switch knob to the "OFF" position to avoid damaging the ammeter or an incorrect current reading.
9. Turn test switch tool knob to the "OFF" position to allow current to flow through the ammeter.
NOTE: If current reading shows in the negative range, turn the test switch tool knob to "ON," reverse the ammeter probes on the test switch terminals, and turn the test switch tool knob to "OFF."
10. Check current reading. If current reading is at or below two amps, turn the test tool knob to the "ON" position (to maintain continuity in the electrical system) and switch down to the two amp scale for a more accurate reading when drain test tool knob is turned "OFF".
IMPORTANT
- Always turn the test switch tool 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.).
11. If current draw is unusually high for the vehicles overall electrical content, remove system fuses one fuse at a time until the current draw returns to an acceptable value. Perform steps 8 through 10 each time a fuse is removed. Refer to the ELECTRICAL DIAGNOSIS section for specific circuit schematics.
IMPORTANT
- On vehicles equipped with a CCM or BCM, check current load readings in "awake" and "asleep" states. Refer to the CCM or BCM Service Manual sections for more information on "awake" and "asleep" states.
12. When cause of excessive current draw has been located and repaired, remove current drain test tool and connect negative battery cable to negative battery terminal.
Please include this procedure in your Service Manuals under Section 6D1 - Battery.