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OM-2032 / Operation and Maintenance Manual
100D20 / Generator Sets
Load Contactor Operating Circuit
Trouble, Symptom & Condition
1. Load contactor (K1) will not
close when control switch (21,
Fig. 1 is held in CLOSE
position. Generator running at
normal voltage. No fault lights
on.
March 28/94 Revised
Probable Cause
a. In addition to defective
wiring and connections in
the AC and DC load
contactor actuating
circuits, the load contactor
may be prevented from
closing for any of the
following reasons:
b. Blown fuse (F1) )1-1; 16,
Fig. 9)
c. Defective (open) relay in
protective module (1-1; 4,
Fig. 9).
d. Defective load contactor
control switch (S5)
(21, Fig. 1).
e. Defective rectifier (CR6)
1-1; 5, Fig. 15).
f. Defective load contactor
coil (K1) )1-1; 6, Fig. 11)
Corrective Action
After checking fuse (F1) in step
(1) below, check all wiring and
connections in the load contactor
circuits on the engine control
panel, the protective relay tray
and power module. Then check
components as follows:
Remove and inspect fuse.
Replace if blown.
Use a jumper with clip and prod
terminals to GROUND terminal
"H" in the test receptacle. If
contactor will now close, replace
module or complete protective
relay tray (12, Fig. 1)
Set AUTO-MANUAL switch (S1)
to AUTO position. connect a
jumper with test prods between
terminals "S" and "R" on the test
receptacle. If the contactor closes,
replace control switch.
Check rectifier output as follows:
With test receptacle terminals "S"
and "R" connected as above,
check voltage to rectifier between
terminals "R" and "H". Voltage
should be 115-V AC.
With test receptacle terminals "S"
and "R" connected as above,
check rectifier output at load
contactor terminals X and Y. If
voltage is not at least 90 V DC,
replace rectifier.
Disconnect leads at load
terminals X and Y. Check coil
resistance between these
terminals. Resistance should be
approximately 100 ohms. If coil is
defective, replace the complete
load contactor.
Chapter 3-1
Page 21
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