Zongshen RX3: Electrical System Maintenance

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Testing the Rear, Brake Light Switch

Disconnect the cable from the rear, brake light switch. Set the digital multimeter for a continuity test. Connect one probe of the multimeter to the black wire of the plug. Connect the other probe of the multimeter to the green/yellow wire of the plug. Check for continuity by operating the brake pedal.

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Horn Circuit

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Fuel Gauge Circuit

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Testing the Fuel Gauge Sensor

Disconnect the plug for the fuel tank float. Set the digital multimeter for the 200 ohm range. Connect the multimeter to the sensor terminals. Connect one of the multimeter probes to the yellow/white wire. Connect the other probe to the green wire. The resistance reading for a full tank of fuel is 8 ohms. The resistance reading for an empty tank is 98 ohms.

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Gear Indicator Circuit

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Speed Sensor Circuit

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Speed Sensor Check

Disconnect the speedometer sensor. Check the voltage supply of the sensor between the green and black/red cables. The supply voltage is 12 volts.

Reconnect the speedometer sensor. Connect the multimeter into the back of the plug between the brown/white and green wires. Slowly turn the wheel and check the voltage, which should be 9.2 volts. This is the signal voltage to the sensor; it will stop six times for each rotation of the wheel.

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Radiator Fan Circuit

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Cooling System Check

When the coolant system reaches its highest temperature, the display will flash. This signals the engine is overheating. Stop as soon as possible, and fix the problem to avoid engine damage.

Check the fan diode.

Turn on the ignition switch. Set the digital multimeter to measure voltage on the 20 VDC Scale.

Check the diode input voltage. Connect the red probe of the multimeter to the black wire of the diode. Connect the black probe of the multimeter either to the green wire, or the chassis. Consult the photograph below to verify the correct placement of the probes. Input voltage to the diode should be 12 volts.



Check the diode output voltage. Connect the red probe of the multimeter to the black/yellow wire of the diode. Connect the black probe of the multimeter either to the green wire, or the chassis. Consult the photograph below to verify the correct placement of the probes. Output voltage from the diode should be 12 volts.

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Check the thermal switch for the radiator fans.

The temperature switch is normally open at room temperature. The temperature at which the switch closes is recorded on a side of the hexagonal nut. The closure temperature is 82 degrees Celsius.

To test the switch, remove it from the radiator. Place the switch in a pan of water, and heat the water temperature higher than 82 degrees Celsius. Configure a digital multimeter for a continuity test, and connect the probes to the terminals.

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Radiator Fan Check

Check the resistance of both electric fans. Configure a digital multimeter for a resistance of 200 ohms. Connect the multimeter to the terminals of the electric fan. Resistance should be 4 ohms.



Check the input voltage to the fans. Configure the multimeter to measure voltage (20 VDC Scale). Disconnect the right electric fan. Connect the red probe of the meter to the black/blue. Connect the black probe of the meter to the green wire. The multimeter should measure 12 volts.

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Engine/Coolant Temperature Sensor

The Engine Control Unit (ECU) of the fuel injection system adjusts the fuel mixture to the engine based upon input from the engine/coolant temperature sensor. This sensor is located in the thermostat housing beneath the fuel tank.

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Testing the temperature sensor.

Configure the multimeter to measure ohms (scale 2K). Connect one probe of the multimeter to the electrical terminal of the sensor. Connect the other probe to the sensor body. At a temperature of 20 degrees Celsius, the resistance should be 555 ohms.

Place the temperature sensor in a container of water. Raise the temperature of the water to 82 degrees Celsius. You should obtain a resistance of .056 ohms at 82 degrees Celsius.

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Thermostat

The thermostat allows coolant to move from the engine through the radiators. The thermostat is installed inside a housing which is placed in the hose which enters the top of the engine.



When the coolant temperature is low, the thermostat valve is closed, keeping the coolant inside the engine. This allows the engine to quickly reach the correct operating temperature during cold weather.

When the coolant temperature rises to 70 degrees Celsius, the thermostat valve opens, allowing the coolant to circulate through the radiators, cooling the engine.