Figure 2-1. Thermocouple System Continuity Check Setup.

TM 55-4920-401-13&P Figure 2-1. Thermocouple System Continuity Check Setup. CABLE position, TEMP indicator should indicate temperature rise as each thermocouple junction is heated. (7) Three continuity possibilities exist: (a) Continuity O.K. Proceed to paragraph (b) Continuity on some, but not all, thermo- couples. Check thermocouples and harness wiring. (c) No continuity. Make a rapid check of all connectors and associated wiring and if no mal- function is detected, make harness check (para a), indicator check (paras b or c) and insulation check (para e) until open circuit point is detected. After discontinuity is detected and repaired, perform ac- curacy test in paragraph b. b. Temperature System Accuracy Check. T h e accuracy check is used to test the entire aircraft temperature system by heating all engine thermo- couples and comparing the temperature displayed on the aircraft temperature indicator with the heater probe temperature displayed on the tester TEMP indicator. Refer to figure 2-2 and proceed as follows: NOTE To check an engine not installed in an aircraft, follow the procedure listed below with the following exception. The check cable (and check cable adapter, if required) must be con- nected to the engine harness junction connector and to the CHECK CABLE receptacle. The temperature of the en- gine thermocouples is read on the tester TEMP indicator by switching the T/C INPUT switch to CHECK CABLE position. (1) Turn FUNCTION SELECT, STD DAY, and MASTER POWER switches to OFF position a n d t u r n P R O B E C O N T R O L f u l l y c o u n t e r - clockwise. (2) Connect BH405 heater cable to HEATER CABLE receptacle on tester and connect junction box to heater cable. (3) Connect as many heater probes having the correct part number to the junction box as there are engine thermocouples. 2-2 Change 4