Note Currently, only the auxiliary heater function is available. At the moment the auxiliary heater is not intended to be operated as a supplementary heater. In vehicles with a high-voltage system, the high-voltage heater (PTC) -Z115- is used as a supplementary heater → Heating, air conditioning; Rep. gr.87. In vehicles with a high-voltage system, the high-voltage heater (PTC) -Z115- can be used for heating the passenger compartment.
Topping up coolant and bleeding coolant circuit → Rep. gr.19 and → Chapter
Incorporation of heat exchanger for air conditioning system and auxiliary heater into coolant circuit of engine → Engine mechanics; Rep. gr.19 (coolant hose schematic diagram).
Note
The -arrows- indicate the direction of coolant flow.
1 -
Heat exchanger for heater and air conditioning unit
Incorporation of heat exchanger into engine coolant circuit → Engine mechanics; Rep. gr.19 (coolant hose schematic diagram).
2 -
Non-return valve
Installed in coolant line between high-voltage heater (PTC) -Z115- and heat exchanger of heater and air conditioning unit.
Install with correct orientation and ensure proper operation
Removing and installing → Engine mechanics; Rep. gr.19
Note Prevents coolant from flowing back from the auxiliary heater (via the high-voltage heater (PTC) -Z115-) to the engine when the auxiliary heater is switched on (and the engine and/or the coolant pump for high-temperature circuit -V467- are not running). If there are customer complaints about poor heat output of the air conditioning system in auxiliary heater mode, make sure the non-return valve is installed with correct orientation and that it works properly. If there are customer complaints about poor heat output of the air conditioning system when the auxiliary heater is switched on (and the auxiliary heater is activated for heating the coolant in place of the -Z115-), make sure the non-return valve is installed with correct orientation and that it works properly.
3 -
High-voltage heater (PTC) - Z115- (with high-voltage heater (PTC) control unit - J848-)
Check; vehicle diagnostic tester in “Guided fault finding” mode (of air conditioning system) and → Current flow diagrams, Electrical fault finding and Fitting locations
Removing and installing → Heating, air conditioning; Rep. gr.87
4 -
Coolant valve for gearbox -N488-
Removing and installing → Engine mechanics; Rep. gr.19
Check; vehicle diagnostic tester in “Guided fault finding” mode (of engine) and → Current flow diagrams, Electrical fault finding and Fitting locations
5 -
Coolant supply to gearbox
Incorporation into coolant circuit of engine (and gearbox) → Engine mechanics; Rep. gr.19 (coolant hose schematic diagram).
Removing and installing → Engine mechanics; Rep. gr.19
Note The -N633- is activated by the respective engine control unit (e.g. by engine control unit -J623-), if heat output is required from the air conditioning system and the “auxiliary heater” function is activated, but the auxiliary heater itself is not activated (the -Z115- is used for the auxiliary heater function instead) or if the vehicle is in electric drive mode; → Current flow diagrams, Electrical fault finding and Fitting locations and vehicle diagnostic tester in “Guided fault finding” mode. If there are customer complaints about poor heat output of the air conditioning system when the auxiliary heater is switched off (with engine running and/or at standstill, irrespective of whether -Z115- is activated or not), make sure the coolant changeover valve 2 is installed with correct orientation and that it works properly → Current flow diagrams, Electrical fault finding and Fitting locations and vehicle diagnostic tester in “Guided fault finding” mode. To ensure that the coolant heated by the -Z115- is conveyed through the heat exchanger of heater and air conditioning unit, the coolant pump for high-temperature circuit -V467- and the coolant valve for gearbox -N488- must be activated as well (by the respective engine control unit). To ensure that the coolant flows into the correct direction, the non-return valves installed in the coolant circuit must be installed correctly and they must work properly. For additional information refer to → Engine mechanics; Rep. gr.19 (coolant hose schematic diagram); vehicle diagnostic tester in “Guided fault finding” mode → Current flow diagrams, Electrical fault finding and Fitting locations.
Removing and installing → Engine mechanics; Rep. gr.19
Note The -V467- is activated by the respective engine control unit (e.g. by engine control unit -J623-), if heat output from the air conditioning system is required → Current flow diagrams, Electrical fault finding and Fitting locations and vehicle diagnostic tester in “Guided fault finding” mode. If there are customer complaints about poor heat output of the air conditioning system when the auxiliary heater is switched off (with engine running and/or at standstill, irrespective of whether -Z115- is activated or not), make sure the coolant changeover valve 2 is installed with correct orientation and that it works properly → Current flow diagrams, Electrical fault finding and Fitting locations and vehicle diagnostic tester in “Guided fault finding” mode. To ensure that the coolant heated by the -Z115- is conveyed through the heat exchanger of heater and air conditioning unit, the coolant changeover valve 2 -N633- and the coolant valve for gearbox -N488- must be activated as well (by the respective engine control unit). To ensure that the coolant flows into the correct direction, the non-return valves installed in the coolant circuit ( → Item and → Item) must be installed correctly and they must work properly. For additional information refer to → Engine mechanics; Rep. gr.19 (coolant hose schematic diagram); vehicle diagnostic tester in “Guided fault finding” mode → Current flow diagrams, Electrical fault finding and Fitting locations.
10 -
Coolant return from gearbox
Incorporation into coolant circuit of engine (and gearbox) → Engine mechanics; Rep. gr.19 (coolant hose schematic diagram).
11 -
Non-return valve
Depending on vehicle version, installed in coolant line between heat exchanger of heater and air conditioning unit and circulation pump -V55- (as shown in illustration), or in coolant line between auxiliary heater and heat exchanger of heater and air conditioning unit → Item.
Install with correct orientation and ensure proper operation
Removing and installing → Engine mechanics; Rep. gr.19
Note Prevents coolant from flowing back via the auxiliary heater to the engine when the auxiliary heater is switched off (and the engine and/or the coolant pump for high-temperature circuit -V467- are running). If there are customer complaints about poor heat output of the air conditioning system when the auxiliary heater is switched off (with engine running and/or at standstill, irrespective of whether -Z115- and the coolant pump for high-temperature circuit -V467- are activated or not), make sure the coolant pump/thermostat is installed with correct orientation and that it works properly. If there are customer complaints about poor heat output of the air conditioning system when the auxiliary heater is switched on (and the -Z115- is activated for heating the coolant in place of the auxiliary heater), make sure the coolant pump/thermostat is installed with correct orientation and that it works properly.
12 -
Circulation pump -V55-
The -V55- is integrated into the auxiliary heater's hose assembly.
Removing and installing → Chapter
Note In electric drive mode (engine not running) the circulation pump -V55- of the auxiliary heater can be activated by the auxiliary heater control unit -J364-. The auxiliary heater control unit -J364- is requested to switch on the circulation pump -V55- via the data bus by the air conditioner operating unit (Climatronic control unit -J255-); vehicle diagnostic tester in “Guided fault finding” mode.
13 -
Auxiliary heating
Removing and installing → Chapter
Note If the -J255- in vehicles with high-voltage system has decided that the auxiliary heater function is required to achieve the desired passenger compartment temperature, the auxiliary heater or the high-voltage heater (PTC) -Z115- are activated depending on various conditions.
14 -
Non-return valve
Alternative fitting location, if not installed at → Item
For additional notes refer to → Item
Note
Installed only if the non-return valve → Item is not fitted
?
Test yourself
A quick Volkswagen Golf quiz: every answer comes with an explanation and a link to the manual page.
Note Currently, only the auxiliary heater function is available. At the moment the auxiliary heater is not intended to be operated as a supplementary heater. In vehicles with a high-voltage system, the high-voltage heater (PTC) -Z115- is used as a supplementary heater → Heating, air conditioning; Rep. gr.87. In vehicles with a high-voltage system, the high-voltage heater (PTC) -Z115- can be used for heating the passenger compartment. 