Technician Service Guide 33367B
11
RESULT IF THE CHARGER IS USED WITH AN
INCORRECT FUSE.
SECTION 6 – CHARGER DC CIRCUIT BREAKER
TRIPS/FUSE BLOWS
Before proceeding, verify the rating of the blown
fuse is correct for the model of charger being
serviced. If the value is lower than specified for the
charger being serviced, install a fuse of correct size
and recheck charger operation. If the DC protection
device is a circuit breaker, the quickest and most
accurate way to eliminate the possibility of a faulty
breaker is to replace the breaker with a known good
one.
There are two modes of failure, instantaneous and
delayed blowing of the DC protection device. If the
DC protection device allows the charger to operate
for a period of time before blowing, this is usually the
result of gradual heating of the protection device.
Inspect the connections to the circuit breaker/fuse
for signs of heat caused by a loose connection,
corrosion, physical damage or otherwise.
If the DC protection device itself passes inspection,
confirm the DC voltage polarity from the battery
system is correct. Disconnect the AC power plug
from the electrical outlet, remove the charger’s
cover, connect the DC output cord to the equipment
charging receptacle and measure the DC voltage
present at test points E and F on the service wiring
diagram. See figure 1. Verify the positive (+) is on
test point E, WHITE DC cordset lead, and the
negative (-) is on test point F, BLACK DC cordset
lead.
If the proper polarity is not measured, locate and
correct the wiring defect. If the correct polarity is
measured at test points E and F, the cause of the
DC protection device opening may be caused by a
shorted SCR. See
Section 4 – SCR Testing.
DANGER: REPLACE THE FUSE OR FUSE
ASSEMBLY ONLY WITH THE CORRECT FUSE
OR FUSE ASSEMBLY. FIRE, PROPERTY
DAMAGE, AND PERSONAL INJURY CAN
RESULT IF THE CHARGER IS USED WITH AN
INCORRECT FUSE.
SECTION 7 – BUILDING CIRCUIT BREAKER
TRIPS/FUSE BLOWS
This condition can be caused by a charger problem,
a “weak” fuse or circuit breaker protecting the circuit,
or an overloaded circuit. If the building AC power
fuse or circuit breaker blows, connect the charger to
other outlets (on different circuits) in the building. If
the charger operates properly on other circuits, have
a qualified electrician check the original circuit. If the
charger causes other fuses or circuit breakers (in the
building) to blow, the charger must be checked for a
problem.
Disconnect both the AC power plug from the outlet
and the DC output plug from the equipment charging
receptacle. Remove the charger cover. Locate the
charger nameplate model number and verify it and
the model number listed on the wiring diagram
specific for the model being serviced match. Inspect
and verify the charger is wired correctly according to
the wiring diagram.
Locate and disconnect the transformer primary coil
leads from the AC fuse(s)/circuit breaker(s), test
points A and B on the service wiring diagram. See
figure 3. Using a continuity tester, measure the
continuity between the two flat blades of the AC
power plug, see figure 8.
Figure 8
If no continuity is measured between the two flat
blades of the AC power plug, replace the
transformer and retest.
If continuity is still measured between the two flat
blades of the AC power plug, disconnect the AC
cordset lead(s) from the on/off power switch. Again,
measure for continuity between the two flat blades of
the AC power plug, as shown in figure 8. If
continuity is still measured between the two flat
blades of the AC power plug, replace the AC cordset
and retest.
If no continuity is measured between the two flat
blades of the AC power plug, isolate each remaining
component (on/off power switch, AC voltage selector
switch and any additional components shown in the
wiring diagram specific for the model being serviced)
in the AC input circuit and measure for continuity.
Replace the failed component(s) that measure
continuity with the replacement service part(s)
specified on the parts list for the model charger
being serviced and retest.
