Failure of the ATC/MODE S Transponder 1

TASK 34-52-00-810-801-A
Failure of the ATC/MODE S Transponder 1

1. Possible Causes

XPDR-ATC/MODE S, 1 [1SH1]
CTL UNIT-ATC/TCAS [3SH]
short to ground at the wiring between circuit breaker (5SH1) and two units (1SH1, 3SH)
C/B-COM NAV/ATC/1 [5SH1]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 34-52-00-740-004	BITE Test of the ATC
ASM 345201
AMM 34-52-12-000-001	Removal of the ATC/TCAS Control Unit
AMM 34-52-12-400-001	Installation of the ATC/TCAS Control Unit
AMM 34-52-33-000-001	Removal of the ATC/Mode S Transponder
AMM 34-52-33-400-001	Installation of the ATC/Mode S Transponder

3. Fault Confirmation
Subtask 34-52-00-865-050-A

A. Make sure that this(these) circuit breaker(s) is(are) closed:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
49VU	COM NAV/ATC/1	5SH1	G11

Subtask 34-52-00-740-050-A

B. Test
(1) If the circuit breaker (5SH1) is trips, refer to Para. 4. C. of this trouble shooting procedure.
(2) Do the BITE test of the ATC AMM 34-52-00-740-004.
(a) If the BITE test is not possible, refer to Para. 4. B. of this trouble shooting procedure.

4. Fault Isolation
Subtask 34-52-00-810-050-B

A. If the circuit breaker (5SH1) is closed, and if the BITE test gives the maintenance message ATC1 (1SH1) :

replace the XPDR-ATC/MODE S, 1 [1SH1] AMM 34-52-33-000-001 and AMM 34-52-33-400-001.

Subtask 34-52-00-810-051-B

B. If the circuit breaker (5SH1) is closed and if the BITE test is not possible:
(1) do a check of the wiring of the 115VAC signal from the circuit breaker (5SH1) to the ATC/Mode S transponder 1 (1SH1) and to the ATC/TCAS control unit (3SH) ASM 345201
(a) If there is no continuity:

repair the above wirings.

(b) If there is continuity:

replace the C/B-NAV/ATC/1 (5SH1).

(2) If the fault continues:

do a check of the wiring of the ground signal at ATC/Mode S transponder 1 pin AC/7 and at ATC/TCAS control unit pin A/4.

(a) If there is no continuity:

repair the above wirings.

Subtask 34-52-00-810-072-B

C. If the circuit breaker (5SH1) is open:

close this circuit breaker.

(1) If the circuit breaker (5SH1) trips:

remove these two units:
. XPDR-ATC/MODE S, 1 [1SH1] AMM 34-52-33-000-001
. CTL UNIT-ATC/TCAS [3SH] AMM 34-52-12-000-001
close the circuit breaker (5SH1).

(a) If this circuit breaker stays closed:

connect the CTL UNIT-ATC/TCAS

1 If the circuit breaker trips again:

replace the CTL UNIT-ATC/TCAS AMM 34-52-12-000-001 and AMM 34-52-12-400-001.

2 If the circuit breaker stays closed:

replace the XPDR-ATC/MODE S, 1 AMM 34-52-33-000-001 and AMM 34-52-33-400-001

(b) If this circuit breaker trips again:

do a check for a short to ground at the wiring between circuit breaker (5SH1) and two units (1SH1, 3SH) ASM 345201.

1 If there is a short to ground:

repair the above wiring.

2 If there is no short to ground:

replace the C/B-COM NAV/ATC/1 [5SH1] .

3 Install these two units:

XPDR-ATC/MODE S, 1 AMM 34-52-33-400-001
CTL UNIT-ATC/TCAS (3SH) AMM 34-52-12-400-001.

Subtask 34-52-00-740-051-A

D. Do the test given in Para. 3.B.

[Rev.8 from Aug 2018] 2026.04.04 04:33:22 UTC