TM 1-2840-252-23-3
G-27
FAULT CODE A2, N2 SET POTENTIOMETER EXPANDED INSTRUCTIONS
Refer to numbered steps in figure 113.
Step 2.
Check harness connector PL1 (figure 201) at DECU and FADEC control panel connector for tight
connections.
Step 3.
Disconnect connector PL1 and FADEC control panel connector to check pins and sockets.
Step 5.
Set the N2 set potentiometer to its lowest setting. With PL1 disconnected, check resistance of N2 set
potentiometer at harness PL1 connector sockets h and z. Limit is3600 - 4200Ω. Check resistance at sockets
z and AA (results are "a"). :Limit is 800 - 1400Ω Check resistance at sockets h and AA (results are "b").
Limit is 4500 - 5500Ω. Use the following equation to check if the low limit of the N2 set potentiometer has
been exceeded:
a b = c
Limit on "c" is > 0.10.
Set the N2 set potentiometer to its highest setting. Check resistance at sockets h and z. Limit is800 1400Ω.
Check resistance at sockets z and AA (results are "d"). Limit is 3600 4200Ω. Check resistance at sockets h
and AA (results are "e"). Limit is 4500 5500Ω. Use the following equation to check if the high limit of the N2
set potentiometer has been exceeded:
d e = f
Limit on "f" is < 0.90.
Step 6.
Set the N2 set potentiometer to its lowest setting. With FADEC control panel connector disconnected, check
resistance at panel connector pins A and B. Limit is 3600 4200Ω. Check resistance at pins B and C (results
are g). Limit is 800 1400Ω. Check resistance at pins A and C (results are "h"). Limit is 4500 5500Ω. Use
the following equation to check if the low limit of the N2 set potentiometer has been exceeded:
g h = i
Limit on "i" is > 0.10.
Set the N2 set potentiometer to its highest setting. Check resistance at panel connector pins A and B. Check
resistance at pins B and C (results are "j"). Limit is 3600 4200Ω. Check resistance at pins A and C (results
are "k"). Limit is 4500 5500Ω. Use the following equation to check if the low limit of the potentiometer has
been exceeded.
j k = l
Limit on "I" i s < 0.90.
Step 7.
Before tightening harness connector PL1 and FADEC control panel connector, be sure that keyway in
harness connectors is aligned with keyways in component connectors.
G-52
