CAPACITIVE PROXIMITY SENSOR FAILURE

TM 5-6350-275-24&P

Table 3-9. Sensors DS Maintenance Troubleshooting - Continued

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

3. CAPACITIVE PROXIMITY SENSOR FAILURE (Figure 3-12), SAIG Appendix E Section 2

Step 1. Make sure 16 vac transformer (5) is properly connected to 120 vac power source.

If disconnected from power source, connect, and go to step 2. Step 2. Turn key (4) on

Prox-Watch II (3) to test position. Press Test Activate push button (2) and monitor test verification

lamp (1).

If Prox-Watch II test verification lamp illuminates, sensor is good.

If lamp does not illuminate, go to step 3.

Step 3. Open access door on Prox-Watch II sensor assembly (3) and make a visual check of fuses (7 and 8).

If fuses are blown, replace and perform self test. If CPS is still inoperative, go to step 4.

Step 4. Set a multimeter to read ac volts. Place multimeter leads across TB1 pins 13 and 14 (6). The meter

should indicate 16 vac.

If multimeter reading is correct, check for the presence of the voltages shown below (TP refers to test

points located on the circuit card assembly):

From

Voltage

TP8

TB1-11

13.7 to 13.9 vdc

TP10

TB1-11

13.0 to 13.4 vdc

TP9

TB1-11

8.8 to 9.2 vdc

If voltage is not correct, replace the PWA (Para. 3-114). If voltage is correct, go to step 5.

Step 5. Check to make sure the interconnect cable to the protected objects is secure and functioning

properly. Check the resistance between the sense wire and the termination wire when removed from

TB1-7 and TB1-8. It should read 100kohms +10%.

If reading is correct, replace the CPS PWA (Para. 3-114).

If reading is not correct, locate and replace the bad wire and/or resistor.

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