4-37
Copyright 2017 Cummins Inc.
TABLE 4-26B. HIGH AC VOLTAGE SHUTDOWN (301)
WARNING
Many troubleshooting procedures present hazards that can result in severe personal inju-
ry or death. Only qualified service personnel with knowledge of fuels, electricity, and machinery haz-
ards should perform service procedures. Review Important Safety Instructions page.
Indicator(s) Possible Cause Corrective Action
“HIGH AC
VOLTAGE ”
shutdown
(301)
message.
3. The problem may be the PT/CT mod-
ule (A36) or the interconnecting wiring
to the PT/CT module.
NOTE: To calculate the “expected A36
output” voltage range, do the follow-
ing:
Determine the ratio between the mea-
sured voltage and the expected volt-
age. The output (18 VAC) of the PT/CT
module will also be reduced by this ra-
tio.
*3. Before starting the generator set, discon-
nect the harness connector from the PT/CT
module (A36) and connect the harness tool
between A36 and its harness connector.
Check the output voltage at the alternator
output terminals and record the voltages.
a. If the voltages are not balanced, go to step 5.
b. If the voltages are balanced, calculate the
expected output voltage from the PT/C mod-
ule (see Note to the left). Measure and re-
cord the outputs from A36 J8 pins 6−5, 4−3,
and 2−1.
If the output voltage is proportional to the
alternator output voltage the A36 module
is OK. Go on to step 4.
If the voltages are not balanced, replace
A36.
*CAUTION: Wearing a wrist strap, set S12 to Off and A32 S5 to Standby before connecting/disconnecting harness plugs.
4. The problem may be in the customer
interface board (A34) or the intercon-
necting wiring.
*4. Disconnect the plugs in the following steps
below with the generator set off then start
the generator set in the idle mode, and mea-
sure voltages with a digital multimeter.
a. Disconnect J3/P3 (blue) and insert the har-
ness tool. Check the voltage into the cus-
tomer interface board with the harness tool
at J3 terminals 4−6, 5−13, and 7−20. Re-
move the harness tool and reconnect J3 and
P3. These voltages should be the same val-
ues measured in step 3b.
If the voltages are balanced, continue in this
step. If the voltages are unbalanced, repair
the harness between the A36 module and
the A34 board.
b. Disconnect J5/P5 on the customer interface
board and insert the harness tool. Check the
voltage out of the customer interface board
at J5 terminals 24−28, 26−28, and 30−28.
These voltages should be the same values
measured in step 3b.
If the voltages are balanced, go to step 5. If
the voltages are unbalanced, replace the
customer interface board.
(Continued)
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