Coolant Fan Control Module -J293-

Special tools, testers and auxiliary items
- Multimeter (Fluke 83 or equivalent)
- VW 1594 connector test kit
- VAG 1527B voltage tester (or equivalent diode type tester)
- VAS 5051 Vehicle Diagnostic Testing and Information System for testing square wave (pressure) signal on vehicles with high pressure sensor - G65 -.

Test conditions
- All fuses OK according to wiring diagram
- DTC memory of A/C control head - E87 - checked - no DTCs stored.
- No compressor shut - off conditions displayed in read measuring value block (Display Group 01, display field 1) for A/C control head - E87 - while engine is running.
- A/C control head - E87 - installed.
- Connectors A and B detached from - J293 -.


High pressure sensor -G65- signal, checking







A - Refrigerant system pressure, "high pressure side" (in bar)
B - Signal ratio of square wave signal
C - Characteristic curve


NOTE:
- Coolant Fan Control (FC) module - J293 - sends a positive signal to A/C control head - E87 - whenever the signal ratio is between 13% (equivalent to approx. 1.2 bar) and 78% (equivalent to approx. 32 bar).
- If the signal ratio is lower than 13% or higher than 78%, no positive signal is sent to - E87 -. Therefore - E87 - does not send a signal to - J293 instructing it to energize A/C clutch - N25.
- If the refrigerant system pressure rises above 32 bar (signal ratio higher than 78%), control unit - J293 will wait until the pressure has fallen below 24 bar (signal ratio lower than 65%) before starting to send a positive signal again.
- Coolant Fan Control (FC) Module J293 - switches coolant fan(s) - V7 - to speed 2 whenever the refrigerant system pressure rises above 16 bar (signal ratio higher than 45%) and when Coolant Fan Control (FC) Thermoswitch - F18 - is closed.. If pressure falls below 12.5 bar (signal ratio lower than 37%) the control unit switches the fans back to speed 1.
- 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 us always switched on automatically whenever the A/C clutch - N25 - is energized (regardless of refrigerant system pressure).
- The refrigerant pressure signal from - G65 - is also input to the Motronic Engine Control Module (ECM) - J220 -. This input is needed in order to react to variable A/C compressor loads dependent of refrigerant system pressure. This signal may or may not appear as a duty cycle on the read measuring value block display.
- Check refrigerant system pressures.