Nordyne SERIES M1B Manuel D’Utilisation

28

the cad cell is operational, replace the primary 
control.

4. If the LED continues to fl ash at the interval 

listed above, verify that the control is not in 
restricted mode. If in restricted mode, reset it. 
If not in restricted mode, replace the control.

5. If the (LED indicator for R7184 control; green 

LED for 7505 control) stays off while the fl ame 
is on, check the cad cell sighting for view of 
the fl ame.

6. If the burner locks out, check the cad cell 

resistance. (See Table 8)

7. If the burner stays running, the system is 

operational.

8. If the (LED indicator for R7184 control; green 

LED for 7505 control) is off, check the cad cell 
assembly after disconnecting the line voltage.

Burner will not start and the LED indicator is 
fl ashing at 2 seconds on, 2 seconds off for 
R7184 (or the green LED is fl ashing for 7505).

•  Hold the reset button down for 1 - 2 seconds. 

If LED indicator continues to fl ash, wait for 
60 - 70 seconds. If it still continues to fl ash, 
replace the primary control.

•  Honeywell R7184 control: To check cad cell 

resistance, press and release the button during 
the run mode, with the igniter off. The LED will 
fl ash to indicate the cad cell resistance. For 
proper burner operation, it is important that 
the cad cell resistance is under 1600 Ohms. 
For cad cell resistance, see Table 8.

•  Beckett 7505 control: To check cad cell 

resistance, unplug the cad cell leads (yellow 
wires) from the control. Measure the resistance 
with a meter in the conventional way (when a 
fl ame is present). For proper burner operation, 
it is important that the cad cell resistance is 
under 1,600 Ohms.

1

0-400

2

400-800

3

800-1600

4

>1600

Necessary when the Furnace is Used with 
Some Central Air Conditioners
If an air conditioner is installed that does not use 
the furnace blower for air distribution and operates 
independently of the furnace, the thermostat 
system must have an interlock to prevent the 
furnace and air conditioner from operating at 
the same time. This interlock system usually 
contains either a “Heat-Cool” switch which must 
be turned to one of the positions to activate heat 
or cool operation, or a positive “OFF” switch on 
the cooling thermostat.

The furnace must also be equipped with an 
automatic damper to prevent cold air from 
being discharged up around the heat exchanger 
(NORDYNE p/n 901996 for furnaces without coil 
cavity, or p/n 901083 with coil cavity). See Figure 
36 or 37. Cold air may cause condensation inside 
the heat exchanger which can rust and lead to 
early failure.