If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con-
tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

FUNCTION PROBLEMS

The machine will not shut off when
the power switch is put in the OFF
position.

Make sure the three-phase
input lines are connected cor-
rectly to the DC-400.

1. Check the Input Power switch

(S1) and the associated leads.
See Wiring Diagram.

2. Perform the Input Contactor

Test.

The Arc Control switch (S5) has no
effect in CV (FCAW/GMAW) mode
when welding with the short circuit
transfer process.

1. Make sure the correct process

and gas are being used.

1. Check the Arc Control switch

(S5) for proper operation.

2. Check the welding Mode switch

(S4), the microswitches, and the
associated wiring.

3. Check to make sure the output

choke control coil is not “open”
or grounded. See Wiring
Diagram.

4. Check resistor R1. Normal

resistance is 15 ohms.

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