Standby Current, Measuring / Fault-Tracing

Standby current, measuring / fault-tracing

Preparations for measuring the standby power consumption

General
Factors such as whether the alarm is on or off or whether any doors are open affect the rate at which the car will reach standby power consumption. The lowest power consumption is reached most quickly if the alarm is on (approximately 12 minutes after activation).
When the car doors are closed, it takes approximately 12 minutes after the last door was shut and the ignition switched off. If any of the doors are open, it takes approximately 20 minutes.
For time considerations, it is recommended that the alarm is switched on. This is the case described below.

Preparations for measuring the standby power consumption




- Check that all the lighting is switched off
- Open the boot lid or tailgate. Use a screwdriver to set the lock to the lock position
- Close and lock the doors. Activate the alarm if an alarm is installed
- Allow the car to reach the lowest electrical consumption, see stand-by current for stand-by current.

Note! Do not open any doors or the test will have to be restarted from the beginning.

- Remove the fuse for the alarm siren
- After approximately 12 minutes, the power consumption should have reached its lowest level, <22 mA for an unalarmed car and <35 mA for an alarmed car.

Connecting the measuring instrument

General
When measuring the power consumption, it will soon become evident if there is power consuming component in the car drawing an excessive amount of the battery capacity. If it is obvious that the car is using more current than the listed limits, check the fuse of each power consuming component. See Stand-by current, consumption value Stand-by Current, Consumption Value.
The curves and graphs supplied should be seen as guide values. The consumption may vary depending on the level of equipment in the car. The contents are for a car with the full equipment level, although not including customer installed power consuming components.
Two different methods of measuring total standby power consumption are described below. The simplest and surest method is to use crocodile clips or battery isolator with multimeter. This minimizes the risk of blowing the instrument's internal fuse and is a simpler way of making the connection.
The car's standby consumption can be measured one of two ways depending on whether you have an instrument with or without crocodile clips. The first alternative below is for an instrument with crocodile clips. The second alternative can be performed with a multimeter.

Measurement method
The battery negative terminal must be connected to measure the total power consumption.

Hint: First select Option 1.

Option 1. Connecting crocodile clips and the multimeter




- Set the crocodile clips and the measuring instrument / multimeter to 10A. Secure the crocodile clips to the battery negative terminal.

Reading off and measuring the total stand-by current
- Read off the power consumption and compare with stand-by current.
Hint: In order to ensure accuracy when taking the reading, change to a lower measurement range as the power consumption falls. See stand-by current for stand-by current consumption.

- The total stand-by current should be <22 mA for an unalarmed car and <35 mA for an alarmed car
- Return the car to its normal status if the stand-by current is OK
- If the result is greater than 25 mA for an unalarmed car or greater than 35 mA for an alarmed car, continue to Measuring and fault-tracing the stand-by current per fuse.
Note! Do not forget to unlock the boot lid or tailgate.

Option 2. Connecting the measuring instrument / multimeter and negative battery terminal

Note! To avoid current surges that could damage the measuring instrument when the battery lead is connected, carry out the following.

- Disconnect the battery negative lead. See Battery, disconnecting Battery Disconnecting.




Set the measuring instrument / multimeter to 10 A.

Note! Check that the connections are secure. If the circuit is broken, the stand-by current must be re-checked from the beginning.




Connect the measuring instrument to the negative battery terminal and ground cable. Connect the ground cable to the body.

Reading off and measuring the total stand-by current
- Detach the ground cable from the negative terminal.
- Read off the standby current consumption and compare with the type curves in stand-by current.
Hint: In order to ensure accuracy when taking the reading, change to a lower measurement range as the power consumption falls. See stand-by current for stand-by current consumption.

- The total stand-by current should be <22 mA for an unalarmed car and <35 mA for an alarmed car
- Return the car to its normal status if the stand-by current is OK
- If the result is greater than 25 mA for an unalarmed car or greater than 35 mA for an alarmed car, continue to Measuring and fault-tracing the stand-by current per fuse.
Note! Do not forget to unlock the boot lid or tailgate.

Measuring and fault-tracing the stand-by current per fuse

Note! If the car is using considerably more current (>20%) than the value shown in the standby current curve, there may be a component fault in the car. For type curves, see stand-by current. Readings should only be taken per fuse if the power consumption exceeds the curve by greater than 20%.

When taking readings with the fuses in place, it is important to ensure that the system fed by the fuse is still carrying current during connection.
- Close and lock the doors (except for the driver's door) and the tailgate or boot lid. Arm the alarm if installed
- Check that all the lighting is switched off




- Use a screwdriver to lock the driver's side door lock
- After approximately 12 minutes, the electrical/power consumption should have reached its lowest level, <22 mA for an unalarmed car and <25 mA for an alarmed car.




- Expose the fuse / fusebox. See Integrated relay/fusebox, engine compartment, replacing Integrated Relay/Fusebox, Engine Compartment, Replacing.
- Set the measuring instrument to the correct range. Connect the instrument to the terminal pin on the reverse of the fuse
- Remove the fuse
- Read off the stand-by current consumption for the relevant component. Compare the value with Stand-by current, consumption value Stand-by Current, Consumption Value.
- If the reading exceeds the values in the table by 20% or more, fault-trace according to the diagnostic trouble codes (DTCs) and the wiring diagram
- Install the fuse and then disconnect the measuring instrument
- Repeat the reading until the faulty component has been localised
- Return the car to its normal status if the stand-by current consumption is OK.

Note! Do not forget to unlock doors and the boot lid or tailgate.

Type curves, stand-by current

Note! The following values are not absolute limits.




From and including 1998 week 15 (open door)




From and including 1999 week 50 (open door)




From and including 2000 week 20 (closed door)