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SHUNT FIELD CIRCUIT VOLTAGE TEST (continued)
PROCEDURE
1. Turn the engine off.
2. Open both of the doors on the control panel end of
the SAE-400 machine. The roof may need to be
removed on some models.
WARNING: Secure the doors in the open position
using the door restraint system. If the
machine does not have a door restraint
system, remove the doors or securely
restrain them to prevent them from falling
closed.
3. Place the rheostat in the maximum position and ver-
ify that the polarity switch is either the positive or
negative position. It must not be in the neutral posi-
tion.
4. Place the remote/local switch in the local position.
5. Place the idle switch in the high idle position, start
the engine and allow it to stabilize at high idle RPM.
6. Locate the 500 Ohm/50 Watt resistor located on the
back of the control panel, just below the 115 VAC
duplex receptacle, and measure the voltage across
it. The voltage should measure about 140 VDC.
If the measured voltage is normal, but there is still no
usable output from the welding generator, perform the
Shunt Field Coil Resistance and Ground Test.
If the correct voltage is not present at the 500 Ohm
resistor, check for voltage at the positive and negative
terminals of the D2 bridge rectifier.
If about 140 VDC is present at the D2 bridge rectifier,
check the wiring between the rectifier, the polarity
switch and the 500 Ohm resistor. If the wiring and con-
nections are all good, the polarity switch may be faulty.
If the voltage is not present at the DC terminals of the
D2 rectifier, check for approximately 125 VAC at the AC
terminals of the D2 rectifier. If this AC voltage is pre-
sent, replace the D2 rectifier.
If AC voltage is not present, check the remote/local
switch, the P8 harness plug and receptacle. Check all
the wiring and connections between the D2 and the D1
rectifiers. See the wiring diagram.
7. Check the Rheostat.
TROUBLESHOOTING AND REPAIR
F-52 F-52
SAE-400 SEVERE DUTY
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