Hobart JET-EX 4 Operation And Maintenance Manual page 83

TROUBLESYMPTOM
AND CONDITION
GENERATOR AND CONTROLS
6. Load contactor
opens during
power delivery.
(cont'd)
7. Output current
cannot be limited
by operating
current limiting
potentiometer.
May 20/89
PROBABLE CAUSE
B. Overvoltage relay (K403)
defective.
C. Load contactor (K402)
defective.
A. Defective current limit-
ing potentiometer (R402)
B. Defective voltage
regulator (VR4020)
TEST, CHECK, AND/OR
REMEDY
B. Check overvoltage relay by
operating the machine under
load and gradually raising
voltage at the voltage
regulator (1, Fig. 3) while
observing voltmeter (6, Fig. 2).
Start with a low voltage
(25-V DC) and gradually
increase voltage until relay
functions to open load
contactor. If relay trips at
less than 32-V DC, replace
relay (2, Fig. 3) and return
old relay to factory for
service.
C. If no fault was found in Step B
replace load contacts (22, Fig. 1).
A. Shut down engine and check
current limiting potentiometer
(4, Fig. 2) with an ohmmeter.
To do this, disconnect plug
from generator voltage
regulator (1, Fig. 3) and take
resistance measurements from
pin 2 to pin 9 and then from
pin 2 to pin 10 on the plug.
For each measurement, slowly
turn potentiometer through its
entire range, while observing
ohmmeter readings. Replace
potentiometer if defective. If
it isn't defective, proceed to
Step B.
B. Replace voltage regulator with
one known to be good, and then
operate the generator set under
sufficient load to observe
current limiting. If current
limiting potentiometer now
controls current properly, send
old voltage regulator to
factory for service.
OM-2049
3-1
Page 21