Dashboard
1. Remove the steering wheel
2. Remove facing of a steering column.
3. Turn out two screws of fastening of a panel of devices which became available after removal of facing of a steering column (see illustration)
4. Remove the instrument panel from the panel.
5. Disconnect the multi-pin plugs on the back of the shield. Before disconnecting the plugs, remove the fixing plastic clips from them (see illustration). Depending on the model, the brackets can be unclenched and removed with a screwdriver or by squeezing the bracket leaders.
The following parts can be removed from the instrument panel without dismantling the instrument panel for this:
- control lights. Their base is combined with a cartridge. When purchasing light bulbs, consider the color of the cartridge. There are 1.1W, 1.2W and 2W light bulbs. To remove the light bulb, just turn it a quarter of a turn to the left.
- instrument illumination lamps.
- atmospheric air temperature indicator. Remove two Phillips screws on the pointer itself and two more on the plug (see 13.0).
- Voltage regulator. Turn out a screw of fastening and disconnect the stabilizer.
- block of control lamps for coolant temperature, brake system and oil pressure (small airborne control system). Loosen the mounting screws and remove the block (see illustration 13.0a). The bulbs of this control unit are located between the speedometer and tachometer
- block for diagnosing the functioning of the main systems of the car (Auto-Check-System). Detachable in the same way as the small onboard control system (small control unit) (see illustration 13.0b). This unit is installed on request instead of the small on-board control system and is an additional vehicle equipment.
- on-board computer. Detachable in the same way as the small airborne control system.
- instrument lighting control resistor. Loosen the two hex nuts and remove the resistor by pulling it back (see illustration 13.0v).
13.0v Instrument panel parts
1 - printed circuit board
2 - atmospheric air temperature indicator
3 - body
4 - small onboard control system (small control unit)
5 - instrument panel backlight resistor
After disassembling the instrument panel, for which it is necessary to first remove the regulating resistor, a small control unit (or onboard computer), as well as unscrew the 11 fixing screws on the back side, provides access to the following tools and pointers:
- speedometer. Remove the four Phillips screws.
- clock with pointer indication. If necessary, first disconnect the coolant temperature gauge.
- tachometer. Remove the three Phillips screws.
- clock with electronic indication. Unscrew the two fastening screws and remove the clock by pushing it forward. Release the clock setting pin from the mount and disconnect.
- fuel gauge and coolant temperature indicator. Unscrew the two nuts and release the pointer from the retaining latches (see illustration 13.0g).
13.0g Disassembled instrument panel
1 - printed circuit board
2 - coolant temperature gauge
3 - tachometer
4 - clock with electronic indication
5 - clock setting pin
Speedometer
On AUDJ 80 cars, the usual flexible shaft speedometer from the gearbox is not installed. The speedometer used is an electronic measuring instrument that functions identically to the tachometer. The speedometer, like the tachometer, receives impulses from a sensor mounted on the gearbox and reading the speed of rotation of the wheels. The speedometer multiplies the received pulses by a time factor, resulting in the vehicle's speed. A so-called stepper motor rotates the odometer drive shaft after receiving a certain number of pulses. The advantages of an electronic speedometer are silent operation and accurate readings. If the speedometer fails, the first thing to check is the appropriate fuse in the fuse box.
Pulses containing the number of wheel revolutions come from a reed switch located on the gearbox on the left side. The reed switch is a contact group in a sealed shell filled with gas. The sensor is triggered when a magnetic field is applied to it. In order for the reed switch to generate impulses corresponding to the speed of rotation of the wheels, the magnetic field acting on it must be interrupted accordingly. To do this, a wheel with cutouts is installed in front of the sensor.
1. Jack up the front left wheel.
2. Remove the bracket holding the plug and disconnect the sensor plug.
3. Connect to both contacts of the gauge an ohmmeter and rotate a forward wheel. The ohmmeter should show resistance from 0 to infinity ohms. If not, then the sensor needs to be replaced.
4. Press the tab holding the sensor, turn the sensor slightly to the right and remove it (see illustration).
When installing a new sensor, make sure the sensor O-ring is properly seated.
Tachometer
The number of revolutions of the crankshaft per minute can be determined by the tachometer. It receives control impulses from the ignition system. These pulses are summed up in the electronic device of the device and transmitted to the mechanism with a pointer. If the tachometer fails, first of all, check the corresponding fuse, as well as the wires. The cause of the malfunction of the tachometer may also be a defect on the printed circuit board of the instrument panel. The tachometer cannot be repaired on its own.
Watch
Only vehicles with a 66 kW four-cylinder engine have a clock with a pointer display fitted as standard on the instrument panel. And only for cars with more powerful engines, a tachometer with a small clock with electronic indication is installed in their place. Both types of watches are quartz.
If the clock does not run, then the cause may be a fuse or a broken wire. Watches with electronic indication are not repaired at all, and with pointer indication - only in specialized workshops.
Fuel gauge
The amount of fuel in the tank is indicated by a gauge on the instrument panel. The fuel gauge is a voltmeter that is energized when the ignition is on. In order for this voltage to be constant, a stabilizer is connected to the pointer circuit. Relevant information about the fuel level in the tank comes from a sensor in the fuel tank. This information is an electrical signal in the form of a resistance value that can be greater or lesser depending on the amount of fuel in the tank.
If the gauge does not display the correct amount of fuel, then the reason for this may be a defective stabilizer or an incorrect gauge setting. If the pointer does not work at all, then the cause of the malfunction may be a defect in the stabilizer, a fuel reserve sensor in the fuel tank, or a failure of the pointer itself.
Fuel gauge - setting
5. «Empty» fuel tank completely.
6. Pour exactly four liters of fuel into the fuel tank.
7. Turn on the ignition and wait two minutes. The fuel gauge needle should be positioned on the first long line in the red colored area. If this does not happen, then the pointer can be adjusted using a small adjustment screw on the left side at the bottom of the shield. To do this, remove the black plug next to the trip mileage reset button and turn the adjustment screw with a hex socket wrench (see illustration).
To check the fuel gauge sensor, unscrew the trunk floor trim and open the black cover.
8. Disconnect the multi-pin plug located under the cover.
9. Connect the auxiliary wire to the terminal to which the purple-black wire is connected, and fix this auxiliary wire to «mass» (-).
10. Turn on the ignition. If the arrow of the fuel gauge on the instrument panel deviates completely, then the sensor power wire and the sensor itself are normal. If the pointer needle does not deviate, then most likely the sensor in the fuel tank is faulty.
If the pointer does not move at all and remains in the position «empty», then a wire break, a defect in the stabilizer of the pointer or the pointer itself is possible. The pointer sensor is probably good.
Coolant temperature gauge
The coolant temperature gauge works in the same way as the fuel gauge.
Power is supplied to it when the ignition is turned on, and «weight» (-) installed on the cylinder block. The coolant temperature gauge sensor is nothing more than a current source with a variable resistance. With an increase in the temperature of the coolant, the current strength increases, heating the bimetallic plate on which the arrow is fixed. When heated, the plate deflects the pointer on the instrument panel. Depending on the type of engine and configuration, two types of coolant temperature sensors can be installed.
- a standard sensor combined with a thermal switch for the coolant temperature warning light, which lights up when it reaches high values. This sensor is installed on vehicles with four-cylinder (petrol and diesel) engines without air conditioning (see illustrations 13.0e and 13.0g).
- electronic thermal switch (with additional features). Installed on vehicles with four, five and six-cylinder engines with air conditioning (see illustrations 13.0h and 13.0e).
Attention! If the coolant temperature is high, a flashing control lamp lights up along with the corresponding indicator reading. For vehicles with a control unit for the functioning of the main vehicle systems installed on the instrument panel, the symbol is displayed «Coolant».
The reason for the incorrect display of the coolant temperature with the simultaneous incorrect indication of the fuel supply may be a defect in the voltage stabilizer on the instrument panel.
If the coolant temperature gauge does not work, then this may be caused by a malfunction of the coolant temperature sensor or the gauge itself.
If the pointer correctly displays the current coolant temperature, but the control light is flashing, then the cause of such a failure may be a malfunction of the coolant level sensor in the expansion tank.
11. Disconnect the multi-pin connector of the coolant temperature sensor in the engine compartment.
12. Fix a separate wire on the plug contact to the coolant temperature gauge on the instrument panel (a wire with blue-brown insulation is connected to it) and attach it to «mass» (-) (see illustrations).
13. Turn on the ignition. If the arrow of the coolant temperature gauge starts to move along the scale, then the sensor is faulty and must be replaced.
If the arrow of the pointer is still motionless, then the cause may be a break in the power wire or a malfunction of the pointer itself.
Voltage regulator
A small block with three wires is attached to the back of the instrument panel. This is the voltage stabilizer. It is designed to maintain a stable voltage supplied to the fuel gauge and coolant temperature gauges. If the arrows of both named pointers «are dancing» or the indicators do not work, then the cause may be a malfunction of the stabilizer.
14. Remove the instrument panel.
15. Connect the power wires to the dismantled shield.
16. Turn on the ignition.
17. Connect the voltmeter to the central and left contacts of the stabilizer, if you look at the shield from behind. The voltmeter should show 9.75-10.25 V. If the voltmeter reading is less than the specified values, then the stabilizer is faulty. If the voltage is not registered at all, then check the power wires. To do this, connect a voltmeter to the central and right contacts of the stabilizer. If the voltmeter does not register battery voltage, then you need to find a wire break (see illustration).
Additional measuring devices
As an option, three measuring devices can be installed on the center console:
- oil pressure gauge
- oil temperature gauge and
- voltmeter
To remove them, the center console must be removed.
To check the pressure gauge and oil temperature gauge, disconnect the wire from the corresponding sensor of these devices and bring the wire to «mass» (-). If at the same time the arrows of these devices do not deviate, then the wire may be broken or the devices themselves are faulty. Otherwise the sensor is faulty (see illustration 13.0i).
To check the voltmeter, check the voltage at the voltmeter contacts. If there is voltage, but the voltmeter does not work, then it itself is faulty.
As already mentioned, a so-called small control unit is installed on the instrument panel, which combines control lights for coolant temperature, brake system and oil pressure.
Control bulb of temperature of a cooling liquid
If this light starts flashing while driving, you must stop and check the coolant level, and top up if necessary.
If the coolant level is normal, then make sure that when the engine is warm, the radiator fan turns on when the ignition is turned on. If it does not work, despite the fact that the heatsink is hot enough, then find and fix the cause of the fan failure.
If the radiator blower fan is functioning normally, the coolant level is also normal, then the reason for the coolant warning light to come on may be a malfunction of one of the sensors to which the warning light is connected.
18. Check the bulb itself and the sensors.
Control bulb of temperature of a cooling liquid
The coolant temperature warning light comes on when the ignition is switched on, when the system is self-testing. If it does not light at this moment, then check the corresponding fuse. If the fuse is OK, then remove the instrument panel, remove the control bulb and check it. If the bulb does not burn out and works, then replace the entire small control unit on the instrument panel.
Coolant temperature sensor
If the coolant temperature warning light on the instrument panel flashes when the engine is cold or warm enough to run, a faulty coolant temperature sensor may be the cause.
19. Disconnect the sensor's multi-pin plug. The indicator light on the instrument panel should go out.
20. Connect the sensor wire going to the test light to «mass» (-). The light should start flashing again (see illustration 13.0e).
This means that the bulb itself is normal, and the cause of the failure is the sensor or a broken wire. Check sensor and wire. Replace sensor if necessary.
In addition, the coolant level sensor in the expansion tank may be the cause of the malfunction of the control light.
21. Check the coolant level sensor in the expansion tank.
22. Disconnect the wire of this sensor, despite the fact that the coolant level in the tank is normal. If, after disconnecting the wire, the control lamp stops flashing, then clean the sensor inside the tank or replace the tank together with the sensor.
Brake warning light
When the ignition is switched on, the control lamp starts flashing, confirming the self-test of the system. When the engine is running, it should go out. If it continues to flash or lights up while driving, the brake fluid level must be checked immediately. It is possible that one of the brake circuits has become depressurized, which should also be felt by the increased stroke of the brake pedal.
23. Check up a control bulb. This check is performed in the same way as checking the coolant temperature warning light.
If the control lamp flashes when the engine is running, although the brake fluid level in the reservoir is above the minimum mark, then disconnect the plug of the brake fluid level sensor in the reservoir. If the control lamp goes out, the brake fluid level sensor is faulty.
24. Replace the tank together with the sensor.
Oil pressure warning light
Oil pressure in AUDI 80 cars is controlled by two pressure regulators and a control unit with an acoustic signal. The control unit and the acoustic signal are elements of the small control unit. In a simplified form, oil pressure control is as follows.
When the ignition is switched on, the oil pressure warning light is energized. If the oil pressure with the engine off is less than 0.3 bar, then the 0.3 bar oil pressure regulator contacts close, creating a connection at «mass» (-) with the second contact of the control light, and the light starts flashing.
When the engine is started, the oil pressure begins to increase and the contacts of the oil pressure regulator open by 0.3 bar, and the light goes out.
For additional control, vehicles with four- and five-cylinder engines have a pressure regulator of 1.8 bar, vehicles with diesel engines have a pressure regulator of 0.9 bar. Six-cylinder engines have a 2.5 bar pressure regulator.
This regulator is also connected to the control unit of the small onboard control system. When the oil pressure drops below 0.9, 1.8 or 2.5 bar, respectively, it closes its contacts, creating a connection on «mass» (-) with the control unit of the small onboard control system. The 0.3 bar oil pressure regulator does not react to the pressure drop in this case..
The small on-board monitoring system only turns on the oil pressure warning light if the oil pressure drop continues for more than one second at engine speeds above 2100 rpm. Additionally, a small on-board monitoring system emits an audible signal. The purpose of this control is to avoid damage to the engine due to low oil pressure in the system, which has arisen, for example, due to a drop in its level.
To make the oil pressure regulators easier to recognize, their insulated ends are colored in different colors.
The 0.3 bar oil pressure regulator is painted brown. On vehicles equipped with an additional oil pressure gauge, in place of this regulator is an oil pressure sensor, which is connected to the oil pressure warning light on the instrument panel (see illustration 13.0i).
The 0.9 bar oil pressure regulator on vehicles with diesel engines is painted grey.
1.8 bar pressure regulator (four- and five-cylinder engines) is painted white, while the 2.5 bar pressure regulator on six-cylinder engines is painted red.
If the oil pressure warning light comes on while driving (possibly accompanied by an audible signal), then you need to stop.
25. Stop the engine.
26. Check the oil level.
27. Disconnect the 0.3 bar oil pressure regulator wire if the oil level is OK and hold the wire so that it does not come into contact with metal (see illustration).
28. Turn on the ignition. If the light is still on, then the wire is shorted to «mass» (-). This does not pose any danger to the engine.
29. Disconnect the 0.9 bar oil pressure regulator wire (1.8 bar, 2.5 bar) and connect it to «mass» (-) (see illustrations).
30. Turn on the ignition. If the control lamp is still on and an audible signal sounds, then the cause of the malfunction is in the smallest control unit or the sensor wire is broken. It also does not pose any danger to the engine.
If the control lamp reacts differently when performing the above checks, then a malfunction in the engine lubrication system itself cannot be ruled out. The vehicle must be towed to a workshop.
It is also possible to loosen the contacts of the oil pressure regulator, which is eliminated by correcting the fit of the regulator.
If the oil pressure warning light does not come on when the ignition is switched on, the corresponding fuse must first be checked.
31. Disconnect the 0.3 bar oil pressure regulator wire and connect it to «mass» (-).
If the control lamp lights up, the oil pressure regulator is defective. Otherwise, the light bulb is burned out or the power wire is broken.
Small on-board monitoring system control unit - check
32. Disconnect the 1.8 bar pressure regulator wire.
33. Fix the wire so that it does not come into contact with metal.
34. Start the engine and let it run at about 2500 rpm. After two seconds, the oil pressure indicator light should come on. At the same time, a three-time beep should sound. If this does not happen, then the small onboard monitoring system is faulty and must be replaced.
If the control lamp lights up, but there is no sound signal, then the connection from the generator terminal 61 is broken (D+).
If, when the wire is connected to the oil pressure regulator and the engine is running at about 2500 rpm, the control lamp lights up and an audible signal sounds, then the oil pressure regulator is faulty, respectively, by 0.9 bar (1.8 or 2.5 bar).
35. Leave the engine to idle and disconnect the wire from the pressure regulator by 0.9 bar respectively (1.8 or 2.5 bar).
36. Fix the wire so that it does not come into contact with metal. If the control lamp and the buzzer turn on again, then the wire from the W terminal is broken (diesel engines) or from terminal 1 (gasoline engines) small control system.
37. Install a new pressure regulator that matches your vehicle's engine, following the color of the regulator. Don't forget to install the o-ring.
38. Tighten the pressure regulator with a torque of 25 Nm, no more.
Direction indicator lamps
On the left and right sides in the upper part of the instrument panel are both control lamps of the direction indicator. They are connected to the turn signal bulbs and therefore flash at the same rate.
If, when the direction indicator is on, the green control lamp on the instrument panel lights up and immediately goes out, then this is evidence that the indicator lamp has burned out.
If, when the direction indicator or warning light is turned on, the control lights do not flash in time with the breaker, then the breaker is faulty. The breaker is also faulty in cases where the blinking cycle of the indicator lights is not constant and they blink either quickly or slowly.
If the turn signal is functioning normally but the alarm is not working, or vice versa, then the cause is a blown fuse or switch.
The turn signal breaker is not located on the main relay box, but is fixed under the instrument panel on the left side. This is done on purpose so that you can hear the characteristic clicks when the breaker is operating.
39. Remove the trim below the instrument panel and remove the breaker (see illustration).
40. Disconnect the breaker plug. Driving with a faulty turn signal breaker is not always safe. In such cases, we recommend doing the following:
41. Disconnect the breaker.
42. Jump between terminals 49 and 49a using a paper clip.
43. Replace the breaker.
When you turn on the turn signal, the indicator lights will be on constantly. The required blinking cycle of the indicators can be created manually using the turn signal stalk switch.
There are a number of warning lights on the instrument panel, including:
- A) Battery charging control lamp. This light should not be on or flashing while the engine is running. If this is not the case, then the power system has failed. If the control lamp does not light up when the ignition is turned on, then it is burned out or the generator wire is broken.
- b) Control lamp for the direction indicators on the trailer. It works in time with the direction indicators on the tow hitch. If one of the direction indicators on the trailer is faulty, the warning light will not come on. The control bulb lights up at inclusion of light alarm system even if one of bulbs of the index of turn is faulty.
- V) Airbag warning light. On vehicles equipped with airbags, this warning light comes on for about 10 seconds. when starting the engine. If it doesn't, replace the bulb. When the engine is running, the lamp goes out. If the control lamp lights up while driving and does not go out after restarting the engine, then this is a signal that there is a defect in the airbag unit. The same can be said if the bulb does not light up at all.
- G) ABS control lamp. For vehicles equipped with an ABS system, the control lamp lights up when the ignition is switched on. If it doesn't, replace the bulb. When the engine is running, the lamp goes out. If the light comes on while driving, the ABS is faulty. On cars manufactured before 6/92, the ABS light comes on when the battery is disconnected.
- d) High beam control lamp. It lights up when switching to high beam or when a signal is given by the headlights. However, a lit indicator light is not a confirmation that the headlight bulb is actually on. It only states that power is supplied to the high beam headlight bulb. Headlight operation must be checked by yourself.
- and) Parking brake indicator light.
If this control lamp does not light up when the parking brake is applied, then the fuse must first be checked.
44. Remove and check the light bulb. If it is OK, then remove the parking brake switch located under the center console panel and disconnect the wire and connect it to «weight» (-) (see illustration).
If in this case the control lamp lights up, the switch is faulty.
If the control lamp does not go out when the parking brake is released, then check in the same way, however, the switch wire in this case is on «mass» (-) don't start. If the light goes out, then the switch is faulty or it is not installed correctly. If the control light is still on, then the power wire is frayed and shorted to «mass» (-).
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