Troubleshooting; Control System Diagnostics - Allied Downflow or Horizontal 2 Stage Heat Variable Speed Gas Fired Non-Condensing Warm Air Furnace Installation And Servicing Instructions

Troubleshooting

Make the following visual checks before toubleshooting:
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 (see page 23).
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.
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 9.
Fault Code History Button
The control stores the last five fault codes in memory. A
pushbutton switch (fault code history switch) is located on
the control (see Page 5). 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.
High Heat State LED
On these models, a green LED is provided on the control
board to indicate high heat state (see Table 10).
CFM LED
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).
20571201
TROUBLE SHOOTING With LED Indicator Assistance
The control continuously
Table 9
Failure Codes - Red LED
LED
Status
No power to control or control hardware fault
LED Off
detected
LED On Normal operation
1 Flash Flame present with gas valve off
2 Flashes Pressure switch closed with inducer off
3 Flashes Low-fire pressure, or IBS switch open
4 Flashes High limit switch or rollout switch open
5 Flashes Not used
6 Flashes Pressure switch cycle lockout
7 Flashes Lockout due to no ignition
8 Flashes Lockout due to too many flame dropouts
9 Flashes Incorrect polarity and phasing
Table 10
High Heat State - Green LED
LED
Status
LED Off No demand for high heat
LED On High heat demand, operating normally
High heat demand, high pressure switch not
LED Flashing
closed
Issue 0527
Fault Description
Description
Page 26 of 28