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
1-800-833-9353(WELD).

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

FUNCTION PROBLEMS

The machine regularly overheats
and the yellow thermal light is ON
indicating a thermal overload.

Check the 3.5 amp circuit
breaker (CB2). Reset if tripped.

2. The welding application may

be exceeding the
recommended duty cycle of the
V350-Pro.

3. Dirt and dust may have clogged

the cooling channels inside the
machine.

4. Air intake and exhaust louvers

may be blocked due to inade-
quate clearance around the
machine.

5. Make certain the fan as needed

(F.A.N.) is operating properly.
The fan should operate when
welding voltage is present
and/or when there is an over
temperature condition.

1. The 115VAC fan motor is con-

trolled by the control board via
the main switch board. Perform
the Fan Motor And Control
Test.

1. A thermostat or associated cir-

cuitry may be faulty. See the
wiring diagram. One normally
closed thermostat is located on
the output choke and the other
is located on the main switch
board heat sink. See the wiring
diagram.

Note: The Main Switch Board

Removal Procedure will be
required to gain access to
the heat sink thermostat.

An attached wire feeder will not
function correctly.

1. Make certain the wire feeder

control cable is connected to
the correct 14-pin amphenol
type plug (115VAC or
24/42VAC) for the wire feeder
being used. See the connection
diagram. If wirefeeder has DIP
switch, be sure it is set correct-
ly.

2. Check the two circuit breakers

located at the rear of the
machine. Reset if tripped.

3. The wire feeder or control cable

may be faulty.

1. Perform the

Auxiliary

Transformer Test.

2. Check the leads between the

14-pin amphenol type plugs and
the auxiliary transformer for
loose or faulty connections.