Servicing electronic heater controls - Thermotronic — VW

Warning!
Always disconnect the battery earth strap before working on the electrical system.
Notes:

Before disconnecting battery, obtain radio code for radios with anti-theft coding.
Remove Thermotronic controls for all tests.
Use leads from adapter set V.A.G 1594 to connect up testers.
Numbers 18 to 28 on the trim are references for the inside temperature. They are not test data.

Temperature flap control motor -V68-
Check end position of control motor when installed =>Fig.
3
Check resistance of control motor potentiometer -G92- when installed =>Fig.
4

Temperature sensor - fresh air intake duct -G89-
Fitting location: in fresh air intake duct behind shelf passenger side.
Check: at 25 °C, resistance should be 10 kω. Resistance decreases with increasing temperature.
Removing and installing: remove cover, right, below dash panel. Turn sensor and pull out of fitting.

Fresh air fan series resistor with overheating fuse -N24-
Removing =>Page 80-1; Servicing heating, Fig.
1

Thermotronic control unit -J214-
Renewing=>Fig.
2

Fresh air and heated air controls
The controls are identical to those on the heater system without electronic regulation. The Thermotronic controls also have the control unit -J214- fitted.

Control panel trim

Trim for dash panel temperature sensor
Temperature sensor - dash panel -G56- and blower for temperature sensor -V42-
Checking temperature sensor: at 25°C, resistance should be 3 kω. Resistance decreases as temperature increases (measure between chambers 4 and 5).
Removing => Fig.
1

Thermotronic wiring loom

Fig.1
Removing dash panel temperature sensor -G56- and temperature sensor blower -V42-

Remove through the radio aperture in the instrument panel

Remove radio.
Pull off trim for temperature sensor.
Release temperature sensor -G56- and blower -V42- with screwdriver (arrows) and take out through radio aperture.

Fig.2
Renewing Thermotronic control unit -J214-

Removing heating and fresh air controls => Page
80-8
, Fig.
3.
Turn Thermotronic centre rotary control -2- past the resistance to the blue end point.
Turn control unit pinion -1- until the marking and the pin are aligned.
Assemble control unit -1- and controls -2-.

Fig.3
Checking end position of control motor -V68- when installed

Pull 5-pin connector off control unit -J214-
Connect cables from adapter set V.A.G 1594 to chambers 4 and 5.
Connect to 12 V supply. Direction of rotation can be changed by reversing polarity of voltage supply.
Move temperature flap -2- with control motor -1- from heater end position -4- to fresh air end position -3-.
Check whether the temperature flap lever -2- reaches the stop when at the end position. If necessary, adjust length of connecting rod -5- with temperature flap -2- on stop.

Note:

If the connecting rod has been loosened, the rotary control is to be turned to the blue mark "cold" and the temperature flap lever must be pretensioned by pressing lightly towards cold and secured (4 clips).

Fig.4
Checking resistance of potentiometer -G92- for control motor -V68- when installed

Pull 5-pin connector off control unit -J214-
Connect cables from adapter set V.A.G 1594 to chambers 4 and 5.
Connect to 12 V supply. Direction of rotation can be changed by reversing polarity of voltage supply.
Measure resistance between chambers 1 and 2 using hand multimeter V.A.G 1526:

Fresh air end position -2-, Specification: 2 kω ±20%
Heating end position -1-, Specification: approx. 0,2 kω