A6 Sedan V6-2.8L (AHA) (1998)
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Mass Air Flow Sensor: Diagnostic Aids
Checking For Voltage Drop
Voltage Drop Test
Checking Voltage drop across connections or components as shown will indicate whether there is abnormal resistance creating an additional load
in the circuit - consuming power and dropping the Voltage available to other parts of the circuit.
NOTE: Voltage drop measurements can only be made when the circuit is powered and there is normal current flow.
Testing For Voltage Drop
The example illustrates troubleshooting the back-up light switch. The switch is in the circuit to switch power to the back-up lights ON and OFF.
When Reverse gear is selected and the switch is closed, it should have very little resistance and not be a consumer.
If dirt or corrosion on the switch contacts creates resistance, some of the available battery Voltage goes into overcoming that resistance. Less
Voltage is available to light the back-up lights, and they will not be as bright.