Diagnostics
36
GMND-SVX01B-EN
F. Gas Odor.
1. Shut off gas immediately!
1. Inspect all gas piping and repair.
2. Blocked heat exchanger/venting.
2. Clean heat exchanger/flue.
3. Drafts around heater.
3. Eliminate drafts. Refer to
“Installation: Mechanical,” p. 12
.
4. Negative pressure in building.
4. See
“Installation: Piping,” p. 16
.
5. Blocked draft hood.
5. Clean draft hood.
G. Delayed ignition.
1. Excessive primary air.
1. Close air shutter. Refer to
“Operation,” p. 26
.
2. Main burner ports clogged near
pilot.
2. Clean main burner ports.
3. Pressure regulator set too low.
3. Reset manifold pressure. Refer to
“Operation,” p. 26
.
4. Pilot decreases in size when main
burners come on.
4. Supply piping is inadequately sized. Refer to
“Installation:
Piping,” p. 16
.
5. Pilot flame too small.
5. Clean pilot orifice. Refer to
“Operation,” p. 26
.
6. Drafts around venter.
6. Eliminate drafts. Refer to
“Installation: Mechanical,” p. 12
.
7. Improper venting.
7. Refer to
“Installation: Piping,” p. 16
.
H. Failure to ignite.
1. Main gas valve off.
1. Open all manual gas valves.
2. Lack of power at unit.
2. Replace fuse or turn on power supply.
3. Thermostat not calling for heat.
3. Turn up thermostat.
4. Defective limit switch.
4. Check limit switch with continuity tester. If open, replace
high limit switch.
5. Improper thermostat or
transformer wiring.
5. Check wiring per diagrams.
6. Defective gas valve.
6. Replace gas valve.
7. Defective thermostat.
7. Check thermostat and replace if defective.
8. Defective transformer.
8. Be sure 115 volts is supplied to the transformer primary,
then check for 24 volts at secondary terminal before
replacing.
9. Loose wiring.
9. Check and tighten all wiring connections per diagrams.
10. Defective ignition control.
10. Replace, if necessary. Also see
U
,
V
, and
W
symptoms.
I.
Condensation of water vapor.
1. Condensation of water vapor.
1. Refer to
“Installation: Venting,” p. 18
.
J.
Burner won't turn off.
1. Poor thermostat location.
1. Relocate thermostat away from drafts.
2. Defective thermostat.
2. Replace thermostat.
3. Improper thermostat or
transformer wiring at gas valve.
3. Check wiring per diagrams.
4. Short circuit.
4. Check operation at valve. Check for short (such as staples
piercing thermostat wiring), and correct.
5. Defective or sticking gas valve.
5. Replace gas valve.
6. Excessive gas supply pressure.
6. Refer to
“Installation: Piping,” p. 16
.
K. Rapid burner cycling.
1. Loose wiring connections at gas
valve or thermostat.
1. Tighten all connections.
2. Excessive thermostat heat
anticipator.
2. Adjust thermostat for longer cycles. Refer to
“Installation:
Electrical,” p. 24
.
3. Unit cycling on high limit.
3. Check for proper air supply across heat exchanger.
4. Poor thermostat location.
4. Relocate thermostat. (Do not mount thermostat on unit).
5. Draft on pilot.
5. Eliminate drafts. Refer to
“Installation: Mechanical,” p. 12
.
6. Defective ignitor control.
6. Replace ignitor.
7. Defective high limit.
7. Jumper limit switch terminals 1 and 2. If burner operates
normally, replace switch.
L. Noisy power venter.
1. Power venter wheel loose.
1. Replace or tighten.
2. Power venter wheel dirty.
2. Clean power venter wheel.
3. Power venter wheel rubbing
housing.
3. Realign power venter wheel.
4. Bearings are dry.
4. Oil bearings on power venter motor. (Refer to label on
motor.)
M. Pilot will not light or will not stay
lit.
1. Main gas valve off.
1. Open all manual gas valves.
Table 8.
Troubleshooting guide (continued)
Symptoms
Possible Cause(s)
Corrective Action
