A/C Control Head -E87-, Electrical Test Summary

A/C Control Head -E87-, Electrical Test Summary

Test Step 1 - 6:

Test step 1 - Voltage supply, Ground (GND) connection, illumination for A/C control head -E87-, signal for "ignition off" period

Test Step 1.1 - 1.2:

Test Step 1.3 - 1.5:

Test Step 1.6 - 1.7:

Test Step 1.8:

Test step 2 - Temperature sensors/sensors (-G17-, G98-, G192-)

Test Step 2.1 - 2.3:

Resistance values (dependent on ambient temperature) for temperature sensors in k Ohm







Test step 3 - Fresh air blower -V2- with control module -J126-

Test Step 3.1 - 3.2:

Test Step 3.3 - 3.4:

Test step 4 - A/C flap position sensors (in flap motors) (-V68-/-G92-, -V70-/G112-, -V71-/-G113-, -V85-/-G114-)

Test Step 4.1 - 4.2:

NOTE:
- The resistance of the potentiometers in the positioning motors can only be measured at the motors themselves (they are connected in parallel) (specification: 3.6 kOhm to 5.7 kOhm , between terminals 1 and 3).
- The resistance of the potentiometers in the flap motors (between terminals 1 and 2 and between terminals 3 and2) depends on the position of the motor, and must always be measured with the motor installed. The maximum specified value will not be obtained in test steps 4.1 and 4.2. To obtain the maximum specified value, all the connectors on the other flap motors would have to be disconnected; (motors are connected in parallel).
- If the A/C control head -E87- detects the malfunction "Potentiometer short circuit to Ground" or "Open/short circuit to B+," test all the potentiometers (one in each of the 5 positioning motors) and the wiring.
- If the readout for DTC memory shows that more than one of the positioning motors is malfunctioning but no DTCs are identified in test step 4, test for short circuits in the wiring to and between the individual positioning motors (e.g. between --V70- and -V71-).

Test Step 4.3 - 4.6:

Test step 5 - A/C pressure switch -F129-, signal from Coolant Fan Control (FC) Module -J293-, output for "A/C compressor cut-in/out", signal indicating "excessive coolant temperature"

Test Step 5.1:

Test Step 5.2:

Test Step 5.3:

Test Step 5.4:

Test Step 5.5:

Test Step 5.6:

Test Step 5.7:

Test step 6 - Activation of coolant fan(s) -V7-, activation of A/C clutch -N25-

Test Step 6.1:

Test Step 6.2:

NOTE:
- On vehicles equipped with A/C pressure switch -F129-, coolant fan(s) -V7- are switched on whenever A/C clutch -N25- is activated.
- Various versions of Coolant Fan Control (FC) Module -J293-, used in conjunction with high pressure sensor -G65- may be installed. At the time of publishing however, All TT equipped with -J293- / -G65- have version where coolant fan(s) -V7- speed 1 is always switched on automatically whenever the A/C clutch -N25- is energized (regardless of refrigerant system pressure).