Truck/Trailer Refrigeration Unit - Sunbelt Transport Refrigeration

4.23 CONTROLLER SENSOR CHECKOUTAn accurate ohmmeter must be used to checkresistance values shown in Table 4-4.Due to variations and inaccuracies in ohmmeters,thermometers or other test equipment, a reading within2% of the chart value would indicate a good sensor. If asensor is bad, the resistance reading will usually be muchhigher or lower than the resistance values given inTable 4-4.At least one lead from the sensor (1RA, terminals D1or E1) must be disconnected from the unit electricalsystem before any reading is taken. Not doing so willresult in a false reading. Two preferred methods ofdetermining the actual test temperature at the sensor,are an ice bath at 0_C(32_F) or a calibrated temperaturetester.Table 4-4. Sensor Resistance -- Micro Units(CDT,1 RA, 2RA, 3RA & WTS)Temperature RAS & WTS CDT_F _CResistanceResistanceIn Ohms In Ohms--- 20 --- 28.9 165,300 1,653,000--- 10 --- 23.3 117,800 1,178,0000 --- 17.8 85,500 855,00010 --- 12.2 62,400 624,00020 --- 6.7 46,300 463,00030 --- 1.1 34,500 345,00032 0 32,700 327,00040 4.4 26,200 262,00050 10.0 19,900 199,00060 15.6 15,300 153,00070 21.1 11,900 119,00077 25 10,000 100,00080 26.7 9,300 93,00090 32.2 7,300 73,000100 37.8 5,800 58,000110 43.3 4,700 47,000120 48.9 3,800 38,000194 90 915 9,150212 100 680 6,800266 130 301 3,010302 150 186 1,8604.24 SUCTION PRESSURE TRANSDUCERA new suction pressure transducer must be calibrated,before it is installed .The calibration will not be performed if the run relayis energized. This prevents the operator from calibratingthe unit with the sensor in the system. The reading of thesensor must be at atmospheric pressure (0 psig or 14.7psi). If the sensor reading is greater than 20 psig (34.7 psi)or less than ---6.7 psig (8 psi) it cannot be calibrated. Oncethe microprocessor is calibrated, the display will readoutthe actual value.a. Turn power off and remove starter solenoid wire,then let unit fail to start. This will de-energize run relay.b. Connect wiring to new suction pressuretransducer. Before installing suction pressure transducerinto unit, display the suction pressure via the unit statusdisplay. While the suction pressure is being displayedpress Enter Key for three seconds. The display shouldread “0”. If display reads “0” install suction pressuretransducer into unit.Table 4-5. Suction Pressure Transducer VoltagePsig Voltage Psig Voltage Psig Voltage20” 0.369 30 0.761 70 1.15510” 0.417 35 0.810 75 1.2040 0.466 40 0.860 80 1.2535 0.515 45 0.909 85 1.30310 0.564 50 0.958 90 1.35215 0.614 55 1.007 95 1.40120 0.663 60 1.056 100 1.45025 0.712 65 1.1064-21 62-02884