Tech Tip No. 12
Originally published in the quattro quarterly
Voltmeter in the Heater Control
Beginning in November 1985 the Audi 5000 line used a digital
climate control system. This system featured digital electronic circuitry, bi-level mode operation, and self diagnostic capability. This system was later improved on other models to even display the
relative speed of the vehicle!
The self diagnostic system has 22 or 23 different channels that
allow you to check different things. Channel 11 displays the voltage of the electrical system.
Here is how you access this bit of information:
1.Press and hold down OUTSIDE TEMP button.
2.While it is pressed, press and release the OFF
button. '01 is displayed. This is channel 01.
3. Press and release the WARMER button. Continue to
press and release it until the display reads '11.
4.Press and release the COOLER button.
The display should read the battery voltage at the control head. If the fan is on it will read a little lower than battery voltage. But you can always turn the fan off before starting the test. If the display simply drops to the lower channel you have even a newer control head which allows you to select channels in a decending order by pressing the COOLER button. If this happens go back to channel 11 and then press the OUTSIDE TEMP button to read the voltage.