Brother NV4000D Service Manual page 352

Failure Investigation for Electronic Parts Automatic needle threader does not work correctly
5 - 26
From previous page
Is the resistance between pins 1 &
1, 2 & 2, 3 & 4, and 4 & 3 at the
ends of the TH pulse motor lead
wire 1 Ω or less?
Y
Is the resistance between pins 1 &
2 and 3 & 4 on the TH and TG
pulse motor connectors normal?
TH pulse motor : 5 - 7 Ω
TG pulse motor : 11 - 13 Ω
Y
Replace main PCB assy.
N
Replace the TH pulse motor
lead wire.
N
Replace the pulse motor.