42
UBX-UBZ-UDX-UDZ-IOM (07-23) 1034344-K
TROUBLESHOOTING—CONTINUED
General Troubleshooting—Continued
Table 20. Circuit Board (DSI Control Module) Display Codes
Display Code Status Display Code Indication
Steady
— Normal operation—no call for heat
0 Ignition sequence active
H Normal operation—call for heat (strong flame)
Flashing
2 Normal operation—call for heat (weak flame)
L Lockout from failed ignition or flame loss
3 Pressure switch is not closed within 30 seconds of venter motor energizing
4 Pressure switch is closed before venter motor is energized
5 Limit switch or rollout open
6 Undesired flame
7 Polarity reversed
Steady Off Internal fault/power failure
Unit Troubleshooting Using DSI Control Module
The SSD on the DSI control module (refer to Circuit Board (DSI Control Module) section) may be used to
troubleshoot the unit. The control module monitors the operation of the heater, and the display indicates normal
operation and various abnormal conditions. If the heater fails to operate properly, check this display (refer to Table
20) to determine the cause and/or to eliminate certain causes. Remove and reapply power to the control module
to view the last five fault codes stored in its memory—the most recent to least recent fault codes will be displayed.
See Figure 20 for a flowchart for troubleshooting the unit using the DSI control module.
NOTES:
• If troubleshooting indicates that repair of the DSI control module is required, note that its only
replaceable part is the fuse (see Figure 10), which is a type ATC or ATO 3A fuse, color code violet
(PN 201685).
• IMPORTANT: When using a multimeter to troubleshoot the 24V circuit, place the multimeter’s test
leads into the connectors located on the ignition control. Do not remove connectors or terminals
from the electrical components. Doing so can result in misinterpreted readings caused by the
control module’s fault mode monitoring circuits.
• Remove and reapply power to the control module to view the last five fault codes stored in its
memory. The most recent to least recent fault codes will be displayed.
Table 19. General Troubleshooting
Symptom Probable Cause Remedy
F. Fan
or venter
motor turns
ON and
OFF while
burner is
operating
1. Motor overload device cycling ON and
OFF
Check motor load against motor rating plate—replace motor if needed
G. Fan
or venter
motor cuts
out on
overload
1. Low or high voltage supply Correct electric supply
2. Defective motor Replace motor
3. Poor airflow Clean motor, fan, and fan guard
—Continued
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