A/C System, Electrical Testing

A/C system, electrical testing

NOTE:
- VAG1598 test box must not be connected to -E87- when performing On Board Diagnostic with VAG1551 Scan Tool (ST)

Test equipment required

- VAG1598 test box with adapter cables VAG1598/11, VAG1598/12 and VAG1594 adapter set
- Fluke 83 multimeter (US 1119) or equivalent
- US 1115 LED tester
- Thermometer

Requirements
- Battery Positive Voltage (B+) OK
- Ground (GND) connections on engine and transmission OK
- Fuse No. 42 (S42), 51 (S51), 225 (S225) and 15 (S15) OK

CAUTION!
Switch multimeter to the appropriate measuring range before connecting the test leads to avoid damaging electronic components.

VAG1598 test box, connecting
- Switch off ignition.
- Remove A/C control head -E87- and disconnect all connectors, -A-, -B-, -C- and -D-.

- Connect VAG1598/11 and 12 adapter cables to corresponding connectors of the vehicle wiring harness (to -E87-).
- Connect VAG1598 test box to the respective adapter cable for performing measurements.

NOTE:
- Do not connect -E87-.
- When using VAG1598/12 adapter cable, the terminal assignment of the sockets is identical with the terminal assignment of - E87-.
- When using VAG1598/11 adapter cable, the terminal assignment of the sockets is not identical to the terminal assignment of -E87-.

Connector terminal assignment of VAG1598 test box with VAG1598/11 adapter cable

NOTE:
- The terminal assignment of VAG1598/11 adapter cable connectors A and B is not identical to the terminal assignment of sockets on the VAG1598 test box.
- The terminal assignment of VAG1598/11 adapter cable terminal C is identical to the terminal assignment of sockets on the VAG1598 test box.
- The terminal assignment of VAG1598/12 adapter cable terminal D is identical to the terminal assignment of sockets on the VAG1598 test box
- As a result of splitting the connectors to A/C control head -E87- using two adapter cables (VAG1598/11 and 12), no ground connection exists for the test when VAG1598/11 adapter cable is connected. When performing various electrical tests, it is therefore necessary to use an external Ground source (vehicle body etc.) or a second VAG1598 test box (when adapter cable VAG1598/12 is connected, Ground exists at sockets 14 and 15).

Electrical testing

Test Number 1 - 6:

Test No. 1 (A/C control head -E87- voltage supply, ground connection and illumination)

Test Step 1.1 - 1.2:

Test Step 1.3:

Test Step 1.4 - 1.8:

Test No. 2 (temperature sensors G17, G56 and G89)

Test Step 2.1 - 2.3:

Temperature sensor resistances (based on ambient temperature, resistance in k ohm)

Test No. 3 (Fresh Air Blower V2 and Control module for fresh air blower J126)

Test Step 3.1 - 3.3:

Test Step 3.4:

Test No. 4 (air/temperature distribution flap motors and related potentiometers)

Test Step 4.1 - 4.2:

Test Step 4.3 - 4.6:

Test No. 5 (A/C Compressor Speed Sensor -G111-, refrigerant pressure switches -F118-, -F73- and Interior Temperature Sensor Fan -V42-)

NOTE: Electrical test steps 5.1 to 5.4 do not apply to vehicles equipped with Nippondenso compressors (A/C compressor speed sensor G111 is not installed on Nippondenso compressors).