Nordyne Downflow Direct Vent Forced Air Gas Oil Furnaces SERIES M1B - Manual (Page 27)

27
120 VAC Is Available At AMP Plug - Ignitor
Does Not Heat Up
1. Disconnect power to the furnace.
2. Disconnect AMP plug to the ignitor, and check
ignitor resistance with an ohm meter. Set on
RX1 scale.
• Normal reading should be 40 - 75 ohms.
• If above or below this rating at room tem-
perature change ignitor.
3. Check for continuity from ignitor receptacle to
burner.
Main Flame Ignites - Burner Locks Out
• Ignition control is not properly grounded.
• Defective ignition control.
• Improper polarity of 120 volt power supply.
• Ignitor has hairline crack.
• Improper gas pressure or burner air adjustment
is not allowing fl ame to contact ignitor tip for
fl ame rectifi cation.
• Misaligned ignitor does not allow fl ame to
contact ignitor tip for fl ame rectifi cation.
Burner Short Cycling - Thermostat Calls for
Heat, Limit Switches Closed
• Check for polarity.
• Check ground.
• Check fl ue.
• Check combustion air.
• Check gas pressure.
• Check orifi ce.
• Check the position of ignitor, a normal reading
should be 40-75 ohms.
24 Volts Supplied To Gas Valve During Ignition
- No Main Gas Flow
• Gas valve may be defective. Replace if
necessary.
• Gas piping may be plugged. Check for
adequate gas supply to gas valve at union.
Burner Operates - Insuffi cient Heat
• Check thermostat for proper setting and
location. Thermostat should not be located
where it will be affected by another heat source.
• Check for clean fi lter and proper air fl ow.
• Check burner for proper gas fi ring rate.
• Be sure unit is not undersized for its thermal
load.
• Check thermostat anticipator. The nominal
setting is 0.4.
Burner Flame Without Motor Running
• Gas valve stuck open, check gas valve for
proper operation (replace if necessary) and
inspect heat exchanger.
• Check for 115 volts to the combustion blower
motor; replace if necessary.
• If no power to combustion blower then check
wiring and control module; replace if necessary.
Circulation Air Blower Will Not Operate Even
Though The Burner Does Operate
• Check thermostat G connection.
• Check wiring to motor.
• Check for a defective motor.
Oil Gun - Honeywell R7184 or Beckett 7505
Controls Only - M5S Series.
Burner does not start with a call for heat.
• Check the electrical supply to furnace.
• Verify the furnace door switch is in the ON
position.
• Check for line voltage (115 VAC) at the oil
primary control.
• Check indicator LED with burner off, no call
for heat (no fl ame). See Table 9 (page 29).
- If green LED indicator is on, the cad cell is
seeing stray light or the cad cell of controller
is defective.
- If green LED indicator is off, go immediately
to step 5.
- If LED indicator is fl ashing (red or green on
Beckett 7505 control), refer to the next step
1 below - Reset primary control.
• Jumper T to T terminals on primary control.
- If burner starts, check thermostat or limit
wiring connections.
- If burner does not start, turn off power. Check
all wiring connections.
- If burner does not start, replace primary
control.
Burner starts and then locks out on safety
with Honeywell R7184 LED indicator fl ashing
½ second on, ½ second off. For Beckett 7505
control, the red LED will fl ash.
1. Reset primary control: To reset the control
from (soft) lockout, the button needs only to be
pressed and released. If the R7184 control is
in restricted mode, press and hold the button
for 45 seconds - until the LED fl ashes once. If
the 7505 control is in restricted mode, press
and hold the button in for 15 seconds until the
red turns off and the yellow LED turns on.
NOTE: Restricted Lockout: If the control locks
out three times in a row without a complete heat
cycle between attempts, the lockout becomes a
restricted (hard) lockout.
2. If the LED indicator stops fl ashing and the
ignition remains off, the primary control could
be defective. If line voltage is present at the
igniter terminals, and there is no ignition,
the igniter is likely defective and needs to be
replaced.
3. If the stops fl ashing, burner turns on, but the
control locks out again, check the cad cell. If