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1. Low or no voltage.
2. Fuse(s) blown.
3. Customer interlock not closed
or connected.
4. Fan Off-On switch in Off position.
5. Time clock, night setback thermo-
stat or field installed controls
open.
6. Freeze protection tripped.
7. Damper motor not operating, or
its end switch not making.
8. Overload protection on motor
starter tripped.
9. Belts loose or broken
10. Bearings seized.
11. Motor may be burned or incor-
rectly wired.
12. Motor overheating.
1. Heat Off-On switch in Off
position.
2. Burner enable relay open
(if applicable).
3. Outside air temperature higher
than On-Off inlet ductstat
(if applicable).
4. Field purge timer open
(if applicable).
1. Manual gas shut-off valve closed.
2. Inlet gas pressure lower than
required gas pressure.
3. Type of gas (Natural, LP) supplied
different from factory required
type.
4. Auxiliary switch on starter not
closed.
5. Air flow switches not closing.
6. High temperature limit switch
open.
7. High or low gas pressure switches
open (if applicable).
8. Main gas valve relay open.
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SECTION VII – TROUBLESHOOTING
Symptom
Cause
Remedy
A. If blower does not operate.
B. If there is no voltage at ignition
control.
C. Burner does not light after 5 sec-
onds pre purge of flame safeguard
relay and there is voltage at igni-
tion control.
1. Check power source.
2. Check and replace.
3. Close or connect customer
interlock.
4. Switch to On position.
5. Check time clock, night setback
thermostat and field installed
controls for proper settings.
6. Reset freeze stat by interrupting
power. Check for proper setting
and burner operation.
7. Check for power at damper motor
and that end switch has been wired
correctly to the N.O. (normally
open) contact. Check that the
linkage is clear and not binding.
8. Push reset button on starter and
check amps.
9. Turn power off and check belts.
10. Check and replace.
11. Turn power off and check motor
and wiring.
12. Check burner firing rate.
1. Switch to On position.
2. Check for power and replace if
necessary.
3. Lower On-Off inlet ductstat
setting.
4. Check for power and replace if
necessary.
1. Slowly open valve.
2. Increase gas pressure.
3. Replace with factory required
type of gas.
4. Check for power and replace if
necessary.
5. Adjust the air flow and external
static pressure to match rating
plate.
6. Correct problem. Reset by pushing
down the reset button.
7. Correct problem. Reset both
switches.
8. Check for power and replace if
necessary.
System without Pilot