Battery (Parasitic) Load Test

PARASITIC LOAD TEST
The electrical circuitry of the Eldorado and Seville requires that the Body Control Module (BCM) and Central Power Supply (CPS) get an initialization charge whenever the battery power is first provided. This initialization occurs with the ignition key in the "OFF" position, and depending on how long the battery has been disconnected, the initial draw may last for several seconds and can range between 0.5 and 9.0 amps.

J 38758 Parasitic Draw Test Switch:

Parasitic Draw Test:

TOOLS NEEDED
- J 38758 Parasitic Draw Test Switch
- Ammeter with at least 10 amp DC current measurement capabilities

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 (cable) 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 with alligator clips.
9. Turn test switch tool knob to the "OFF" position to allow current to flow through the ammeter.
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 to the two amp scale for a more accurate reading. Turn test tool knob to "OFF". If current reading is above two amps, refer to the standby current drain chart for specific current loads and microprocessor "time-outs" for PCM and CCM/BCM in "awake" and "asleep" states.

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).

11. If current draw is above specifications listed in the standby current load chart, remove system fuses one fuse at a time until the current draw returns to a value less than or equal to the specifications listed. Perform Steps 9 and 10 each time a fuse is removed.
12. When cause of excessive current draw has been located and repaired, turn current drain test tool to, remove tool, and reconnect negative battery cable to negative battery terminal.

ALTERNATE PARASITIC LOAD TEST

Alternate Parasitic Load Diagnosis Procedure:

Component Parasitic Loads:

NOTE: The following alternate procedure may be used when testing for parasitic loads if J 38758 is not available:

1. DISCONNECT BATTERY NEGATIVE CABLE

2. INSTALL SIDE TERMINAL ADAPTER
^ Install a battery side terminal adapter, AC-Delco ST-1201 or equivalent, in the negative terminal of the battery.

3. INSTALL NUT TO CABLE
^ Install the other ST-1201 or a 3/8" nut with standard threads (16 UNC) on the negative battery case attaching screw to assure a good electrical contact with the metal face on the cable for testing (add a washer behind the nut if the nut does not contact firmly). Yellow or black finish nuts are generally non-conductive and should not be used.

4. INSTALL HIGH CAPACITY AMMETER
^ With all lights, accessories, Retained Accessory Power (RAP), and the ignition switch off, connect a high capacity ammeter (at least 10 amps) from the negative battery cable to the side terminal adapter This high capacity ammeter is connected to verify whether or not a high current draw is occurring at a constant rate. It is this type of high current draw which will blow the fuse in lower capacity ammeters. Current is drawn for some time to initialize the CPS. After the initial draw occurs, the ammeter reading should drop below 1 amp.

NOTICE: If a high capacity ammeter is not available, install a section of heavy wire (preferably battery cable section) between the existing battery negative cable and the side terminal adapter. Allow ample time (approximately 30-60 seconds) for the initial draw to occur or check for reduced current with an inductive ammeter (current clamp) and proceed to next step.

5. INSTALL DVM
^ With the high capacity ammeter or battery cable section still connected, connect the digital multi-meter, set on the 2000 DC mA range, in parallel with the high reading ammeter.

6. DISCONNECT HIGH CAPACITY AMMETER
^ Disconnect the high capacity ammeter and take the reading with the digital multi-meter. A current draw of 5O mA or less (25 mA is normal) indicates that all lights and accessories are off and that there is no unexplained current draw. Care should be taken to allow for a time delay before reading the meter because of the Electronic Level Control feature.

7. DETERMINING THE SOURCE OF THE DRAIN
^ Once it has been determined that a parasitic drain in excess of 50 mA exists, a visual inspection of the vehicle should be conducted. Check to see if there are any unwanted lights on, motors running or switches/relays activating.

Component Parasitic Loads:

8. CHECK CHARGING SYSTEM
^ If a battery becomes discharged and no excessive current drain is found in Step 2 above, the operation of the charging system should be checked.
^ If no cause for the draw is immediately apparent, it may be possible to narrow in on the source by systematically removing fuses and circuit breakers, one by one, from the fuse panels. This should be done while monitoring the ammeter so that a disruption of the drain will be evident. Refer to Figure for average and maximum parasitic loads for various vehicle components.

9. DRIVER RELATED CONDITION
^ If no cause is found for a discharged battery and the battery tests good, a light may have been left on, or the driving habits of the owner may be such that, especially with many short trips and repeated starts, the generator does not get a chance to recharge the battery between starts.
^ If this situation is suspected, the driver should be instructed in ways to reduce battery drain. Limiting the use of the rear window defogger and setting the Twilight Sentinel on the minimum delay, etc, are helpful in this regard.