34 Ambient Air Sensor Open Circuit MP4000

Description

Ambient Air Sensor Open Circuit 

  • When the sensor circuit resistance is above 1785Ω. 
  • Indicates: 
  • Open circuit. 
  • Defective or wrong sensor. 
  • Defective wiring. 
  • Defective controller. 

Corrective Action 

  • Check for damaged sensor wires. 
  • Check sensor connections at controller. 
  • The sensor is a pt1000 – 2 wire sensor, connected to the MP-4000 at connector J3 pin 9 and 10. CM-4000 upper left connector J3, 17 pin wide, pin number 1 is the right pin, seen at the backside of the controller. 
  • The 2 sensor wires can be switched without affecting the measurement. 
  • Disconnect the sensor, use an Ohm (Ω) measuring device, measure the electrical resistance between the two sensor wires. 
    • The sensor can’t be examined without disconnecting it. 
    • The electrical resistance towards chassis must be above meg ohm (MΩ) range. 
  • The sensor is a pt1000 – positive temperature coefficient, which means that the electrical resistance of the sensor increases with temperature. 
    • The sensor is defined to be 1000Ω@ 0°C. 
    • Normal condition measuring with disconnected sensor is 960Ω@-10°C, 1000Ω@0°C,1039Ω@+10°C, 1058Ω@+15°C, 1078Ω@+20°C. 
    • The valid measuring limit for this pt1000 sensor is -100°C(602Ω) +200°C(approx 1758Ω).

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