The light indicator does not work in 5th (highest) gear and during sudden engine braking. On models produced in 1984 and later, the indicator light works in all gears except reverse.
Figure 8.7. Components included in the fuel-efficient driving mode indicator system: 1 – to the spark plug; 2 – ignition coil; 3 – damper (delay valve); 4 – vacuum switch; 5 – suction pipe; 6 – 5th gear engagement sensor; 7 – forced idle economizer switch; 8 – carburetor; 9 – battery; 10 – ignition switch; 11 – control unit; 12 – Over-throttle indicator; 13 – high gear engagement indicator; 14 – to the control lamp switch
In addition to the indicator lights themselves, the main components of the system are: a control unit located under the switch panel or instrument panel; a vacuum-operated switch connected to the suction pipe via a damper (delay valve); 5th gear engagement sensor mounted on the gearbox; carburetor-mounted idle speed economizer switch (figure 8.7).
The control unit and the idle economizer switch are combined with the air-fuel mixture depleter when driving in neutral gear.
The control unit receives signals from the sensor and switches, voltage from the power supply and signals from the ignition coil. The signal from the ignition coil allows the control unit to monitor the crankshaft speed.
Technical condition check
High gear indicator light
Start the engine and let it idle.
Gradually increase the engine's crankshaft speed and make sure that the high-gear warning light turns on at a speed of 2800 min⁻1 and remains on when the engine speed increases further.
Figure 8.8. Location of the 5th gear sensor connector, which is part of the fuel-efficient driving mode indicator system
Disconnect the connector from the 5th gear shift sensor (located next to the battery) and check again (figure 8.8). The indicator lamp should not light. Connect the connector.
Over-throttle warning light
This test will require a vacuum pump and a vacuum gauge.
Figure 8.9. Checking the vacuum switch of the fuel economy indicator system
Disconnect the vacuum hose from the switch and connect a vacuum pump and vacuum gauge in its place (figure 8.9). Turn on the ignition. An assistant will be needed to observe the indicator lamp while the vacuum in the switch is increasing. The control lamp should light up at a vacuum of 0 to 120 mm Hg and go out as the vacuum increases.
Figure 8.10. Location of the 5th gear shift sensor
On pre-1984 models, disconnect the connector from the 5th gear switch and retest (figure 8.10). The indicator lamp should not light. Connect the connector and vacuum hose to the 5th gear shift switch.
Replacement of components
Control lamps and indicators
Remove the instrument cluster glass and replace the indicator lamp.
Vacuum switch
Remove the vacuum hose and disconnect the connector from the switch. Remove the switch from the bracket on the car body.
Install the new switch, connect the hose and connector.
5th gear shift sensor
Along the wire route, locate the 5th gear engagement sensor and disconnect the connector from the sensor.
Remove the sensor from the gearbox. Please note that this may cause oil spillage.
Install the new sensor, connect the connector, then check the transmission fluid level.
Control unit
Access to the control unit is possible after removing the lower decorative trim of the instrument panel, switch panel or instrument cluster.