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A/C Control Head - E87-




NOTE: The VAG 1598 test box and adapters must never be connected to the A/C control head - E87 - while performing an on board diagnostic program with VAG 1551/1552 Scan Tool (ST).


Special tools, testers and auxiliary items







- VAG 1598 test box with VAG 1598/11 and VAG 1598/12 adapter cables
- Multimeter (Fluke 83 or equivalent)
- VW 1594 connector test kit
- VAG 1527B voltage tester (or equivalent diode type tester)
- Temperature sensor with suitable tester

Test conditions
- All fuses OK according to wiring diagram

Connecting VAG 1598 test box to connector for A/C control head - E87 - using VAG 1598 adapters 11 and 12
- Switch ignition off.
- Remove A/C control head - E87 -.
- Connect adapter leads VAG 1598/11 and 12 to connectors on vehicle wiring harness.


NOTE:
- Do not connect A/C control head - E87 -.
- To carry out the measurement, connect the VAG 1598 test box to the relevant adapter lead.
- The socket assignment on VAG 1598/12 adapter corresponds exactly to the terminal assignment on the A/C control head - E87 -.
- The socket assignment on VAG 1598 adapter does not correspond to the terminal assignment on the A/C control head - E87 -.


Socket assignment for VAG 1598 test box with adapter lead VAG 1598/11


Connectors A, B & C:






NOTE:
- The terminal assignment for connectors A and B on the VAG 1598/11 adapter does not match the socket assignment on the test box.
- The terminal assignment for connector C on the VAG 1598/11 adapter corresponds exactly to the socket assignment on the test box.
- The terminal assignment for connector D on the VAG 1598/12 adapter corresponds exactly to the socket assignment on the test box.
- Because the connectors for the A/C control head - E87 - are distributed over two adapter leads (VAG 1598/11 and VAG 1598/12) there is no Ground (GND) connection for testing purposes when only adapter lead VAG 1598/11 is connected. Therefore, for various steps of the electrical test it is necessary to use a suitable Ground (GND) point on the body of the car, or to use a second VAG 1598 test box. With the VAG 1598/12 adapters the Ground (GND) connection is through terminal 15.)



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 and 2) 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).
- Test step 6.2 should only be carried out on vehicles equipped with A/C pressure switch -F129-.
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