Table K3: LED Code Troubleshooting
LED
Code
System
Description
Actions
None
No power
to T1
On call for heat, nothing happens.
Check for open fuse or circuit breaker.
Check for poor wiring connection.
Check for failed 24V transformer.
Check if the manual reset high limit switch has tripped and
determine cause and correct before resetting.
Steady on
No
operation
24 VAC across terminal 24 VAC/V2-GND when
thermostat calling for heat.
System fault. Repeated lockouts (five) during continuous call
for heat.
Check input voltage and inlet gas pressure during operation.
Check for condensate or blockage in air tube or pressure
switch.
Check for blocked vent condition or obstruction in heat
exchanger tubes.
Control fault; replace ignition control.
2 Flashes
Open limit
switch
Thermostat call for heat. No power across
terminals V1/V2 on control.
Check for proper operation of circulating air supply system and
for air filter blockage.
Check manifold pressure when limit cools and closes. Natural
gas 3.5” w.c./LP gas 10.0” w.c.
Low combustion blower air output. Flue gas temperature
exceeds 550°F. Inspect for debris accumulation, proper wheel
attachment, proper voltage to blower.
1 Flash
Airflow
fault
Pressure switch contacts in closed position for 30
seconds with no output to combustion blower.
Remains in this mode with combustion blower off.
Check for short in wiring to pressure switch.
Check pressure switch for closed contacts (with leads
disconnected).
Replace pressure switch.
1 Flash
Airflow
fault
Open pressure switch or flame rollout switch
when inducer (IND terminal) is energized. If switch
remains open for more than 30 seconds after
combustion blower is energized, control will remain
in this mode with IND terminal (blower) energized.
Failed combustion blower.
Check connections and air tube from draft inducer to air switch
for leaks.
Check rollout switch manual reset; depress reset.
Check supply tube from draft inducer housing to pressure
switches for condensate; drain line and re-connect.
Check pressure switch for condensate accumulation.
Replace pressure switch.
2 Flashes
Flame
fault
Flame sensor failure/flame present with no call for
heat.
Check for voltage to gas valve with thermostat in ‘Off’ position.
Valve should not be powered.
If valve is not energized, check for gas flow (manifold pressure
reading greater than 0). If gas flow is present, turn off main
shut-off valve and replace gas valve.
VCES-VHC-IOM-1F – VHC-36, -42 & -50
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