PROBLEM 4: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER

ENERGIZES, IGNITOR IS ENERGIZED.

Condition

Possible Cause

Corrective Action/Comments

 

 

 

4.1

4.1.1

ACTION 1 − Check line pressure at the gas valve.

 

Pressure should not exceed 13" WC for both nat-

 

 

− Unit operates with a cooling and

Check that gas is being supplied to

ural and propane. Line pressure should read a

continuous fan demand.

the unit.

minimum 4.5" WC for natural and 8.0"WC for pro-

pane.

 

 

− Combustion air inducer energizes

 

 

4.1.2

 

with Heating demand.

 

Miswiring of gas valve or loose-

ACTION 1 − Check for correct wiring and loose

 

− Ignitor is energized but unit fails to

connections. Correct wiring and/or replace any

connections at multi−pin control amp

light.

loose connections.

plugs or valve.

 

 

 

 

 

 

 

 

ACTION 1 − Check that 24V is supplied to the gas

 

4.1.3

valve approximately 35 seconds after heat de-

 

mand is initiated.

LED#1−Alternating Slow Flash

 

Defective gas valve or ignition

ACTION 2 − Replace the valve if 24V is supplied

 

LED#2−Alternating Slow Flash

control.

but valve does not open.

 

ACTION 3 − Replace the control board if 24V is

 

 

 

 

not supplied to valve.

 

 

 

PROBLEM 5: BURNERS LIGHT WITH A HEATING DEMAND BUT UNIT SHUTS DOWN

 

PREMATURELY

 

 

 

 

Condition

Possible Cause

Corrective Action/Comments

 

 

 

 

5.1.1

ACTION 1 − Check for restricted intake and ex-

 

Low pressure differential at the prove

haust vent. Remove all blockage.

 

ACTION 2: Check for proper vent sizing. See

5.1

switch.

installation instructions.

 

 

− Burners fire with a heating demand.

5.1.2

ACTION 1 − Check vent termination kit installed.

− Burners light but unit shuts off prior

Wrong concentric vent kit used for

See Placement and Installation section.

to satisfying T−stat demand.

terminating the unit.

 

− Diagnostic lights flash the pressure

 

 

 

ACTION 1 − Check condensate line for proper

switch code.

5.1.3

vent slope, and any blockage. Condensate

 

 

 

Condensate drain line is not draining

should flow freely during operation of furnace.

 

properly.

Repair or replace any improperly installed con-

LED#1−Off

densate lines.

 

LED#2−Slow Flash

5.1.4

ACTION 1 − Check for restricted intake and ex-

 

Low pressure differential at the prove

haust. Remove all blockage.

 

ACTION 2: Check for proper vent sizing. See

 

switch.

installation instructions.

 

 

 

5.2

5.2.1

ACTION 1 − Check that sensor is properly lo-

 

 

− Combustion air inducer energizes

Sensor or sense wire is improperly

cated and that the sense wire is properly at-

with a heating demand.

installed.

tached to both the sensor and the control.

 

− Burners light but fail to stay lit.

 

 

5.2.2

ACTION 1 − Check for a broken sensor.

− After 5 tries the control diagnostics

ACTION 2 − Test continuity across the sense

flash the watchguard burners failed to

Sensor or sense wire is broken.

wire. If wire or sensor are damaged replace the

ignite code.

component.

 

 

5.2.3

ACTION 1 − Check for resistance between the

 

sensor rod and the unit ground.

 

 

LED#1−Alternating Slow Flash

Sensor or sensor wire is grounded to

ACTION 2 − Check for resistance between the

sensor wire and the unit ground.

LED#2−Alternating Slow Flash

the unit.

ACTION 3 − Correct any shorts found in circuit.

 

 

 

 

 

 

 

ACTION 1 − Check the microamp signal from

 

 

the burner flame. If the microamp signal is be-

 

 

low normal, check the sense rod for proper

 

 

location or contamination.

 

5.2.4

ACTION 2 − Replace, clean, or relocate flame

 

Control does not sense flame.

sense rod. If rod is to be cleaned, use steel

 

wool or replace sensor. DO NOT CLEAN ROD

 

 

WITH SAND PAPER. SAND PAPER WILL

 

 

CONTRIBUTE TO THE CONTAMINATION

 

 

PROBLEM. NOTE: Do not attempt to bend

 

 

sense rod.

 

 

 

Page 51

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Image 51
Lennox International Inc G61MP Continuous fan demand Unit, Ignitor is energized but unit fails to, Light, Plugs or valve

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