speedometer and tachometer not working

• 2022-04-13

The speed control system used in the vehicle includes: off-on switch, set-acc switch and coast switch, servo (throttle actuator) assembly, speed control sensor, amplifier assembly, safety valve assembly, vacuum holding box and vacuum connector, as well as the required wiring and linkage. The switches are placed on the hub of the steering wheel. The amplifier assembly is located under the instrument panel. The servo assembly is either attached to the engine watch board (such as Ford, mercury, meteor, Torina, Montego and kuger), or attached to the engine intake manifold (such as Thunderbird, Lincoln continent and Mark IV). The speed control sensor is either installed in the passenger compartment (such as Ford, mercury, meteor, torlinna, Montego and kuger), or in the engine compartment (such as Thunderbird, Lincoln Continental and Mark IV).

When operating the speed control system of the vehicle, the engine shall be in working state and the vehicle speed shall be within the range of 30 ~ 80 mph. Then, turn the off-on switch on the steering wheel, and the control system can accept the vehicle speed signal set by the driver. Once the vehicle speed stabilizes at the set speed, press the set-acc button and then relax, the vehicle speed will remain unchanged unless the driver sets a new speed, or presses the brake pedal, or cuts off the control system.

If the new set speed is lower than the existing speed, the driver can step on the brake to slow down the car, and then press the set-acc button when it is stable at the new set speed. You can also press the brake and press the coast switch to slow down the car to the new set speed, and then release the coast switch to maintain the new set speed. However, if the speed drops below 30 miles per hour, you need to accelerate the car first and then reset the speed. If the newly set speed is higher than the existing speed, the driver can step on the accelerator first to increase the vehicle speed and stabilize it at the required speed. Press and release the set-acc button, and the car will maintain the newly set speed. You can also just press and hold the set-acc button. At this time, the car accelerates. When the required speed is reached, release the button and the car will remain at this speed.

When the speedometer and tachometer not working, should check the following items:
(1) Check whether all visible parts of the system are abnormal, whether the wires are peeled off and whether the vacuum hose is damaged. All hoses shall be shunted correctly and connected firmly;
(2) The speedometer cord must also be properly placed and must not be excessively bent or twisted together. The joint shall be firm;
(3) Servo mechanism (i.e. throttle actuator) and pull rod shall work smoothly;
(4) The empty stroke of the traction chain shall not be greater than 1 / 4 inch;
(5) Electrical connectors must be complete and firm;
(6) The wire harness must be neat. Check whether there is insulation peeling and whether the connector is loose or short circuited; The above necessary corrections shall be made before continuing other inspections.