60
UEZ-IOM (07-23) 1034347-I
—Continued
Unit Troubleshooting Using 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 26), 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.
• See Figure 37 for a flowchart for troubleshooting the unit using the DSI control module.
TROUBLESHOOTING—CONTINUED
Unit Troubleshooting Using DSI Control Module—Continued
Table 27. General Troubleshooting
Symptom Probable Cause Remedy
C. Burner
cycles ON
and OFF
1. Gas pressure too high or too low Supply pressure should be 5–14 IN WC for natural gas or 11–14 IN WC for
propane
2. Burner not grounded Ensure that integrated circuit board is grounded (terminals P1–9)
3. Circuit board not grounded Ensure that integrated circuit board is grounded to furnace chassis
4. Faulty integrated circuit board If 24V power is available to integrated circuit board and all other causes have
been eliminated, replace board
5. Pressure switch not closing Perform following:
Ensure that unit is properly vented
Remove obstruction(s) from vent
Replace faulty tubing to pressure switch
6. Faulty pressure switch Replace pressure switch
7. Flame sensor grounded Ensure that flame sensor lead is not grounded or that sensor insulation or
ceramic is not cracked—replace as required
8. Cracked ceramic at sensor Replace sensor
9. Incorrect polarity Reverse line volt leads to integrated circuit board
10. Pin terminal loose on wire harness Replace wire harness
D. No heat
(heater
operating)
1. Incorrect valve outlet pressure or orifice Check valve outlet pressure (refer to unit rating plate for manifold pressure)
2. Cycling on limit control Check air throughput
3. Improper thermostat location or
adjustment
Refer to thermostat manufacturer's instructions
E. Fan
or venter
motor will
not run
1. Circuit open Check wiring and connections
2. Defective integrated circuit board Replace board
3. Defective motor Replace motor
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
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