Condenser Fan: Description and Operation

(Alldata Editor's Note: VW does not provide easy access to Description and Operation information for the cooling fans V7 and V35. Below is a brief explanation of the various inputs from the cooling and air conditioning systems which effect cooling fan operation. Always refer to the appropriate wiring diagrams when diagnosing cooling fan faults.)

Coolant Fan Control

The Coolant Fans (V7/V35) are primarily controlled by the following:
- Coolant Fan Control (FC) Thermal Switch F18
- Coolant Fan Control (FC) Control Module J293
- A/C Pressure Switch F129 (via J293), if equipped
- High Pressure Sensor G65 (via J293), if equipped

When A/C is off:
- F18 switches the fans on to first speed when coolant temperature is within first stage switching temperature range.
- F18 switches the fans on to second speed (via J293) when coolant temperature is within second stage switching temperature range.

When A/C is on:
- J293 switches the fans on to first speed.
- If equipped, A/C Pressure Switch F129 switches the fan(s) to the second speed (via J293) when refrigerant circuit pressure increases.
- If equipped with High Pressure Sensor G65, J293 switches the fan(s) to the second speed if the refrigerant system pressure rises.

Coolant Fan Control (FC) Thermal Switch F18
Switching temperatures:
1st stage
On: 92 - 97 �C
Off: 84 - 91 �C
2nd stage
On: 99 - 105 �C
Off: 91 - 98 �C

Coolant FC (Fan Control) Control Module J293





Note: Available in different construction styles, some separate some installed on radiator fan.


This control module switches on and off the A/C clutch and therefore the A/C compressor. It switches the coolant fan and calculates the pressure in the refrigerant circuit on vehicles with High Pressure Sensor G65 or A/C Pressure/temperature Sensor G395.

A/C Pressure Switch F129






F129 has three functions:
- Switches the A/C clutch N25 off (via J293) when excessive refrigerant circuit pressure is present (e.g.: insufficient air flow over condenser or when overcharged).
- Switches the A/C clutch N25 off (via J293) when insufficient refrigerant circuit pressure is present (e.g.: when refrigerant has leaked out)
- Switches on the second speed coolant fan V7 when refrigerant circuit pressure increases.

Note:
- The presence of F129 is engine dependant. Where F129 is not used, high pressure sensor G65 is used instead.
- Always confirm system use of either F129 or G65 and applicable wiring circuit using applicable "Engine" and "Air conditioning" wiring diagrams.
- A/C Pressure Switch F129 replaces the A/C Refrigerant High Pressure Switch F23, A/C Refrigerant Low Pressure Switch F73 and the A/C Refrigerant High Pressure Switch F118.

High Pressure Sensor G65






Where applicable, High Pressure Sensor G65 transmits a square wave signal to Coolant Fan Control (FC) Control Module J293 at a rate which varies according to the refrigerant system pressure.

J293 reacts to the pulse rate of the signal from G65 as follows:
- If the refrigerant system pressure rises, J293 switches the radiator fan(s) to the second speed.
- Where excessive or insufficient refrigerant system pressure is present (E.g.: insufficient air flow over condenser or when overcharged), Coolant Fan Control (FC) Control Module J293 switches the A/C Clutch N25.
- On Climatronic equipped models it informs the A/C Display Control Head E87 that the pressure in the refrigerant system is OK and that A/C Clutch N25 can be switched on via J293).

On applicable engines, the signal generated by G65 is also provided as an input to the Motronic Engine Control Module (ECM). As the amount of torque needed to drive the A/C compressor varies according to the refrigerant system pressure, the ECM processes this signal in order to enhance engine performance.

Note:
- The presence of G65 is engine dependant. Where G65 is not used, A/C pressure switch F129 is used instead.
- Where G65 is used, its wiring circuit varies according to engine application (E.g.: some are connected to the ECM, some are not).
- Always confirm system use of G65 and applicable wiring circuit using applicable "Engine" and "Air conditioning" wiring diagrams.