45
RPB-IOM (06-22) 131782-B
TROUBLESHOOTING
NOTE: If the furnace is equipped with electronic modulation option AG39 or AG40, see Figure 15
for additional troubleshooting guidelines.
Refer to Table 19 to troubleshoot the unit.
Table 19. General Troubleshooting
Symptom Probable Cause Remedy
A. Venter
motor will not
start
1. No power to furnace Turn ON power and check supply fuses or circuit breaker
2. No 24V power to venter relay Turn up thermostat and check control transformer output
Check for loose or improper wire connections
3. Defective venter relay Replace defective part
4. Defective motor or capacitor Replace defective part
B. Pilot will
not light
with venter
operating
1. Manual valve not open Open manual valve
2. Air in gas line Bleed gas line
3. Dirt in pilot orifice Remove pilot orifice and clean with compressed air or solvent
4. Gas pressure too high or too low Adjust gas pressure (refer to Measure and Adjust Manifold (Outlet) Gas
Pressure section)
5. Kinked pilot tubing Replace tubing
6. Pilot valve does not open If 24V power is available at valve, replace valve
7. No spark
a. Loose wire connections Ensure that all wires connections are solid
b. Transformer failure Ensure that 24V power is available
c. Incorrect spark gap Maintain spark gap at 7/64 inch
d. Spark cable shorted to ground Replace worn or grounded spark cable
e. Spark electrode shorted to ground Replace pilot if ceramic spark electrode is cracked or grounded
f. Drafts affecting pilot Ensure that all panels are in place and are tightly secured to prevent drafts
at pilot
g. Ignition control not grounded Ensure that ignition control is grounded to furnace chassis
h. Faulty ignition controller If 24V power is available to ignition controller and all other causes have been
eliminated, replace ignition control
8. Optional lockout device interrupting control
circuit due to above causes
Reset lockout by interrupting control at thermostat
9. Faulty combustion air proving switch Replace combustion air proving switch
C. Pilot lights
but main
valve will not
open
1. Manual valve not open Open manual valve
2. Main valve not operating
a. Defective valve If 24V power is available at valve connections and valve remains closed,
replace valve
b. Loose wire connections Check and tighten all wiring connections
3. Ignition control does not power main valve
a. Loose wire connections Check and tighten all wiring connections
b. Flame sensor grounded, pilot lights, and
spark continues
Ensure that flame sensor lead is not grounded and that insulation or ceramic
is not cracked; replace as required
c. Incorrect gas pressure Adjust gas pressure (refer to Measure and Adjust Manifold (Outlet) Gas
Pressure section)
d. Cracked ceramic at sensor Replace sensor
e. Faulty ignition controller If all checks listed in Spark Ignition System Maintenance section indicate
no other cause, replace ignition controller (do not attempt to repair ignition
controller, which has no field-replaceable parts)
f. Poor microamp signal Adjust pilot regulator
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