Coolant temperature gauge (VW Golf 1)

The coolant temperature gauge works similarly to the fuel gauge. When the ignition is on, the device receives this. The connection "to ground" is created by a sensor in the thermostat housing or at the cylinder head. The sensor is a variable resistance; when heated, the resistance opens the way for electric current: the bimetallic part in the device heats up more strongly, the device's pointer deflects. After August 1979, an additional red flickering LED was installed in the device to signal that the coolant temperature was too high.

Possible malfunctions

Incorrect reading of coolant temperature and simultaneously inaccurate reading of fuel level may indicate damage to the voltage stabilizer.

If there are no readings, then there is a defect in the sensor or device.

Instructions for checking devices

Checking the temperature sensor: remove the yellow-blue or yellow-red wire from the sensor and securely connect it to the ground (housing).

Turn on the ignition briefly. If the arrow moves into the red area and the LED in the device flickers, this means that the temperature sensor is defective.

Checking the indicator: remove the instrument panel.

The arrow on the scale has tolerance fields: three white lines mark the neutral and final positions of the arrow.

Check: In neutral position, is the arrow within the tolerance range?

For further testing of the indicator, a charged 9V battery is best as this is the working voltage.



Keep the battery terminals close to the pins located at the back.

(The original text is available on the portal: «VWmanual»)

The arrow should deflect: if not, then the poles need to be changed.

When the reading is correct, the arrow moves along the scale to the opposite tolerance area.



If, despite the prescribed correct battery voltage, the final position of the arrow is not reached, the pointer must be replaced.

For further inspection, remove the central connector.

Connect the contact of the black wire (terminal 15) in the central connector to the pole of the 12 V battery.

Connect the purple-black wire contact to the minus (fuel gauge) or yellow-blue, or yellow-red cable (temperature indicator).

If the arrow does not move, then the circuit in the board is open.

If the arrow moves to its extreme position, then there is a defect in the power supply wire.

LED test: press the negative terminal of the 9V battery to the middle clamp behind the indicator light; plus connect to the side contact.


The LED should now be flickering.

If the LED does not work when checking the temperature sensor (but at the moment it is flickering), this means there is a defect in the board.

The red flashing LED in the temperature gauge does not change, only with the device.