Brother BAS-311G Troubleshooting, Problem, Cause, Remedy, Reference, Upper thread breaks

10. TROUBLESHOOTING

Problem

Cause

Remedy

Reference

Upper thread breaks.

Upper thread tension is too strong.

Adjust the upper thread tension.

P. 89

Needle is incorrectly installed.

Install the needle correctly.

Instruction

manual

Thread is too thick for the needle.

Select a thread that matches the needle.

P. 89

Thread

take-up

spring

tension

and

Adjust the tension and height

of

the

P. 90

height are incorrect.

thread take-up spring.

Damage or burring of the rotary hook,

Repair or replace the problem part.

needle hole plate or needle.

Thread

breaking

from

heat

(Synthetic

Use a cooling tank.

Instruction

thread)

manual

Thread is threaded incorrectly.

Thread the thread correctly.

Instruction

manual

Lower thread breaks.

Lower thread tension is too strong.

Adjust the lower thread tension.

P. 89

Damage to corners of needle hole plate

Repair or replace the problem part.

or bobbin case.

Skipped stitches occur.

Clearance between needle

and rotary

Adjust the needle clearance.

P. 92

hook tip is too great.

Needle

and

rotary

hook

timing

is

Adjust the needle bar lift amount.

P. 91

incorrect.

The driver is covering the needle more

Adjust the driver needle guard.

P. 91

than necessary.

Needle is bent.

Replace the needle.

Needle is incorrectly installed.

Install the needle correctly.

Instruction

manual

Needle is broken.

Adjust the needle clearance.

P. 92

Clearance between needle and rotary

hook tip is too great.

Adjust the needle bar lift amount.

P. 91

Needle is bent.

Replace the needle.

Select a needle that is suitable for the

Needle deflection

sewing conditions.

P. 89

Reduce the sewing speed.

Needle is too thin.

Select a needle that is suitable for the

P. 89

sewing conditions.

Thread jamming.

Thread

take-up

spring

tension

and

Adjust the tension and height

of

the

P. 90

height are incorrect.

thread take-up spring.

Needle

and

rotary

hook

timing

is

Adjust the needle bar lift amount.

P. 91

incorrect.

Shuttle

race

thread

guide is

not

Adjust the position of the shuttle race

P. 92

separating the threads.

thread guide.

142 BAS-311G, BAS-326G