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Control Diagnostics
Troubleshooting
Make the following visual checks before troubleshooting:
1.
Check to see that the power to the furnace and the
integrated ignition/blower control board is ON.
2.
The manual shutoff valves in the gas line to the furnace
must be open.
3.
Make sure all wiring connections are secure.
4.
Review the Sequence of Operation.
Start the system by setting thermostat above room
temperature. Observe system response. Then use the
information provided in this section to check the system
operation.
The furnace has a built-in, self-diagnostic capability. If a
system problem occurs, a fault code is shown by a red LED
on the control board. The control continuously monitors its
own operation and the operation of the system. If a failure
occurs, the LED will indicate the failure code. The flash
codes are presented in Table 16.
Fault Code History Button
The control stores the last five fault codes in memory. A
pushbutton switch is located on the control (see Figure 44).
When the pushbutton switch is pressed and released, the
control flashes the stored fault codes. The most recent fault
code is flashed first; the oldest fault code is flashed last. To
clear the fault code history, press and hold the pushbutton
switch in for more than 5 seconds before releasing.
Page 36 of 39
High Heat State LED
On 80G2UH-V models, a green LED is provided on the
control board to indicate high heat state (see Table 17).
CFM LED
On 80G2UH-V models equipped with a variable speed
motor, an amber LED is provided on the control board to
display CFM. To determine what CFM the motor is delivering
at any time, count the number of times the amber LED
flashes. Each flash signifies 100 CFM; count the flashes
and multiply by 100 to determine the actual CFM delivered
(for example: 10 flashes x 100 = 1000 CFM).
LED Status
LED Off
LED On
1 Flash
2 Flashes
3 Flashes
4 Flashes
5 Flashes
6 Flashes
7 Flashes
8 Flashes
9 Flashes
Table 16. Failure Codes - Red LED
LED Status
LED Off
LED On
LED Flashing
Table 17. High Heat State - Green LED
Issue 2302
Fault Description
No power to control or control hardware
fault detected
Normal operation
Flame present with gas valve off
Pressure switch closed with inducer off
Pressure switch open with inducer
energized
Primary Limit, Secondary Limit, or Roll-Out
switch open
Not used
Pressure switch cycle lockout
Lockout due to no ignition
Lockout due to too many flame dropouts
Incorrect polarity and phasing
Fault Description
No demand for high heat
High heat demand, operating normally
High heat demand, high pressure switch
not closed
507335-03
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