This is a reprint of something I posted at the Yahoo Alfa 75 group.
The warning lights on the ARC panel are:
Engine oil level warning light -
To fix, replace sensor with a tested second hand sensor
or replace sensor with 100 ohm resistor (actually leave the sensor in place but connect the wires from the ARC to a 100 ohm resistor instead.
Coolant level warning light -
There are two types of sensor (I think),
1/ a float on a wire with the switch in the cap.
2/ a black plastic tube with a white float at the bottom, the float has a 'ring' magnet in it and inside the tube is a circuit board with a reed switch (small glass capsule very fragile) on it. Reed switches are commonly used in house alarm systems for door/window switches. When the float is lifted by the coolant, the magnet keeps the reed switch closed.
Shorting the wires together will stop the ARC flashing however the switches can be repaired:
Type 1, - To fix, replace the float with a cork
Type 2, - To fix, on my 75 when the float was as high as it could go, it had actually gone above the point where the switch closed to a point where the switch opened again. I don't know why. To fix the switch, where the wires go in there is a thin plastic cover - pry this off. Next you will see some black glue, scrape this away around the edges (its only thin) and you should be able to remove the circuit board. The circuit board has two sets of two holes in it, one set with copper tracks going to them ( this is where the reed switch is ) and another set slightly higher. Moving the reed switch up to the second set of holes fixed my problem. WARNING reed switches are VERY fragile do not apply any force on the glass capsule, when bending the leads hold the lead with a pair of long nose plyers between the glass and the bend. Re-assemble then test with a meter.
Windscreen washer liquid level warning light -
To fix, shorting the wires together will stop the ARC flashing. Better yet, replace the float.
or
Handbrake warning light -
or
Brake pad, brake fluid level warning light -
To fix, a continuous circuit is formed from the ARC through each of the brake pad sensors and a relay switched by a float in the brake fluid reservoir. If this circuit is broken anywhere the ARC warning will flash. If you have brake pads without sensors the wires which go to the sensors must be shorted together.
(From Jon) Later models work in reverse where shorting will cause the annunciator to flash, the brake fluid sensor is wired in parallel and will cause both the stop globe and (!) lights to flash. There is no relay in later cars. As mentioned previously I had trouble with the brake light switch actuator. This problem can be diagnosed by placing your foot under the brake pedal and pushing the pedal up to see if the flashing stops. If this cures the problem it is simply a matter of adjusting the microswitch travel by means of the screw thread and locknut on the microswitch.(/Jon)
Parking lights and rear fog lights efficiency warning light. -
To fix, replace blown bulbs.
Stop lights bulbs/switch/fuse/connectors efficiency warning light -
To fix, replace blown bulbs/fuse, check connector to stop light switch, replace stop light switch.
(From Jon) Again it might be the travel on this switch that causes the problem. The ARC works by sampling the continuity or lack of in the various components of the braking system. For example each lamp circuit is sampled through a current resistor and the current is compared to a nominal value any departure from this value will cause the alarm to flash. It is a good idea to clean all contacts and use the correct wattage lamps in all circuits.(/Jon)
Warning lights warning light -
To fix, I have no idea
(From Jon) This is sensed by current flowing through all the warning lamps in the dashboard, not including the dimmed circuits.(/Jon)
Alternator warning light. -
To fix, repair Alternator.
(From Jon) The alternator warning light senses the direction of current flow in the alternator charge discharge circuit. When the ignition switch is turned on but the motor is not started ther is a current dumping resistor on the ARC circuit board to compensate, this resistor gets quite hot and may fail if the engine is not started for prolonged periods. in which case the alarm will flash continuously and the alternator will possibly be still OK. (/Jon)
(From Luca) Check fuses board, near pedals. Clean, check grounds. Probably that will solve all! (/Luca)
On top of these we also have three other warning lights.
In the Fuel Gauge we have the Low Fuel warning light.
In the Coolant Temp Gauge we have the Over Temp warning light.
In the Oil Pressure Gauge we have the Low Oil Pressure warning light.
