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Form I-UDA, P/N 195673 R24, Page 36
PROBLEM PROBABLE CAUSE REMEDY
Venter motor will not
start
1. No power to unit. 1. Turn on power, check supply fuses or circuit breaker.
2. No 24 volt power to integrated circuit board. 2. Turn up thermostat; check control transformer output.
3. Integrated circuit board fuse blown. 3. Correct cause. Replace fuse (type ATC or ATO, 32VDC, 3A).
4. No power to venter motor. 4. Tighten connections at circuit board and/or motor terminals.
5. Integrated circuit board defective. 5. Replace integrated circuit board.
6. Defective venter motor. 6. Replace venter motor. See Paragraph 29.
Burner will not light 1. Manual valve not open. 1. Open manual valve.
2. Air in the gas line. 2. Bleed gas line (initial startup only).
3. Gas pressure too high or too low. 3. Supply pressure should be 5" - 14" w.c. for natural gas or 11" - 14" w.c. for
propane.
4. No Spark:
4.
a) Loose wire connections a) Be certain all wire connections are solid.
b) Transformer failure.
:
b) Be sure 24 volts is available.
c) Incorrect spark gap. c) Maintain spark gap at 1/8".
d) Spark cable shorted to ground. d) Replace worn or grounded spark cable.
e) Spark electrode shorted to ground. e) Replace if ceramic spark electrode is cracked or grounded.
f) Burner not grounded. f) Make certain integrated circuit board is grounded (Terminal P1-9).
g) Circuit board not grounded. g) Make certain integrated circuit board is grounded to furnace chassis.
h) Unit not properly grounded. h) Make certain unit is properly eld grounded to earth ground and properly
phased (L1 to hot lead L2 to neutral).
i) Integrated circuit board fuse blown. i) Correct cause. Replace fuse (type ATC or ATO, 32VDC, 3A).
j) Faulty integrated circuit board. j) If 24 volt is available to the integrated circuit board and all other causes have
been eliminated, replace board.
5. Lockout device interrupting control circuit by
above causes.
5. Reset lockout by interrupting control at the thermostat or main power.
6. Combustion air proving switch not closing. 6.
a) Make sure unit is properly vented.
b) Remove obstructions from vent.
c) Replace faulty tubing to pressure switch.
7. Faulty combustion air proving switch. 7. Replace combustion air proving switch.
8. Main valve not operating. 8.
a) Defective valve. a) If 24 volt is measured at the valve connections and valve remains closed,
replace valve.
b) Loose wire connections b) Check and tighten all wiring connections.
9. Integrated circuit board does not power main
valve.
9.
a) Loose wire connections. a) Check and tighten all wiring connections.
b) Flame sensor grounded. b) Be certain ame sensor lead is not grounded or insulation or ceramic is not
cracked. Replace as required.
c) Incorrect gas pressure. c) Supply pressure should be 5" - 14" w.c. for natural gas or 11" - 14" w.c. for
propane.
d) Cracked ceramic at sensor. d) Replace sensor.
Burner cycle on and
off
1. Gas pressure too high or too low. 1. Supply pressure should be 5" - 14" w.c. for natural gas or 11" - 14" w.c. for
propane.
2. Burner not grounded 2. Make certain integrated circuit board is grounded (Terminal P1-9).
3. Circuit board not grounded. 3. Make certain integrated circuit board is grounded to furnace chassis.
4. Faulty integrated circuit board 4. If 24 volt is available to the integrated circuit board and all other causes have
been eliminated, replace board.
5. Combustion air proving switch not closing. 5.
a) Make sure unit is properly vented.
b) Remove obstructions from vent.
c) Replace faulty tubing to pressure switch.
6. Faulty combustion air proving switch. 6. Replace combustion air proving switch.
7. Flame sensor grounded. 7. Be certain ame sensor lead is not grounded or insulation or ceramic is not
cracked. Replace as required.
8. Cracked ceramic at sensor. 8. Replace sensor.
9. Incorrect polarity. 9. Reverse line volt leads to integrated circuit board.
10. Pin terminal loose on 9 pin plug. 10. Replace wire harness.
General Troubleshooting
10.3 Troubleshooting (cont’d)
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