Drain Testing Procedures
DRAIN TESTINGNOTE: A voltmeter is sometimes used for this test but it will react to a very small normal drain caused by always-on electronic systems such as starter interlock, anti-theft alarm and illuminated entry, which cause no concern. The test lamp shows only drains which are large enough to cause a concern.
Check for current drains on the battery in excess of 50 milliamps with all the electrical accessories off and the vehicle at rest. Current drains can be tested one of three ways:
1. Connect a 12-volt test lamp in series with battery positive terminal. If lamp glows, then a drain exists.
2. Use a clamp-on current probe to the battery positive or negative cable. Make sure that the probe is properly calibrated to prevent false readings.
3. Use an in-line ammeter between the battery positive or negative post and its respective cable.
Clamp On DC Ammeter Test Procedure
1. Turn the ignition switch OFF and make sure there are no electrical loads. After determining that the engine compartment lamp is turning off properly, disconnect the lamp.
2. Clamp the meter clip securely around positive or negative battery cable (all cables if two or more lead to post).
NOTE: Do not start vehicle with clip on cable.
The current reading (current drain) should be less than 0.05 amp. A current drain greater than 0.05 amp indicates a constant current drain which could cause a discharged battery.
If the drain is not caused by a vehicle lamp, remove the fuses one at a time until the cause of the drain is located. If drain is still undetermined, disconnect leads at starter relay one at a time to find the problem circuit.
With Multimeter, In-Line Test Procedure
Use a digital volt amp-ohmmeter with an appropriate ampere scale such as Rotunda 73 Digital Multimeter 105-R0051 or equivalent.
1. Turn ignition switch OFF and make sure there are no electrical loads. After determining the engine compartment lamp is turning off properly, disconnect the lamp.
2. Check battery voltage. If voltage is under 11.5 volts, charge the battery to above 11.5 volts.
3. Disconnect battery ground cable.
4. Connect ammeter assembly as shown in the illustration provided.
CAUTION: Do not crank the engine because the ammeter could be destroyed. Also do not use the ammeter to measure starting currents.
5. Set ammeter to dc amperage scale for an accurate reading.
The current reading (current drain) should be less than 0.05 amp. If the reading is between 0.2 and 0.9 amp, a possible drain may be a vehicle lamp (such as glove compartment, engine compartment, luggage compartment) that does not turn off. If the problem is not a lamp, remove the fuses one at a time until the cause of the drain is located. If still undetermined, disconnect leads at starter relay one at a time to find the problem circuit.