Haier GE APPLIANCES NF96US Service Manual page 17

Problem
Pressure switch stuck closed
Pressure switch does not close due to obstruction in
vent pipe
Pressure switch does not close due to incorrect
routing of the pressure switch tubing
Pressure switch does not close due to obstructions in
the pressure switch line
Pressure switch tubing damaged
Condensate in pressure switch tubing
Pressure switch does not close due to a low
differential pressure across the pressure switch
Wrong pressure switch installed in the unit, or
pressure switch is out of calibration
Miswiring of furnace or improper connections at
pressure switch
Pressure switch failure
Damaged condensate trap
Cold end header box does not drain properly
Air leakage around the combustion air inducer gasket
Air leakage around the cold end header box gasket
Damaged cold end header box tubing
1
ON
OFF
DEMAND
CAI
IGNITOR
GAS VALVE
INDOOR BLOWER
*Blower on time will be 30 seconds after flame is sensed. Blower off time will depend on "OFF TIME" Setting.
31-5000728 Rev. 0
Table 6. Pressure Switch Troubleshooting Guide
15
Pre -Purge Ignitor Warm-up
Check that the pressure switch is open without the combustion air inducer
operating. Replace if defective.
Check for restricted vent. Remove all blockage.
Check for proper vent sizing. See Table 10A through Table 10F.
Check that the pressure switch tubing is correctly routed. Correctly route
pressure switch line.
Remove any obstructions from the the pressure switch line and/or taps
Check pressure switch tubing for leaks. Replace damaged tubing if
necessary.
Check pressure switch tubing for condensate. Remove condensate from
tubing.
Check the differential pressure across the pressure switch.
Check for restricted inlet vent. Remove all blockage.
Check for proper vent sizing and run length. See Table 10A through Table
10F.
Check that the correct pressure switch is installed in the unit. Replace
pressure switch if necessary.
Check for correct wiring and loose connections. Correct wiring and/or replace
any loose connections.
If all the above modes of failure have been checked, the pressure switch
may have failed. Replace pressure switch and determine if unit will operate.
Check trap for any cracks or damage and replace if necessary.
Check that the furnace is set properly with a slight tilt (0 - 1/2") towards the
front if necessary. See furnace installation instruction.
Check gasket and replace if necessary.
Check gasket and replace if necessary.
Check tubing and replace if necessary.
34
38
Trial for
Blower "On"*
Ignition
Figure 12.
Page 17
Corrective Action
80
Delay
5 SEC
Post
Purge