Nordyne M1B Troubleshooting, Direct Ignition Furnaces Including Gas Gun, Ignitor Does Not Heat Up

humidity requires higher temperatures for the same level of comfort. Check for proper humidity level in the home.

TROUBLESHOOTING -

DIRECT IGNITION FURNACES INCLUDING GAS GUN

Burner Motor Does Not Run—

Thermostat Calls For Heat

a. Check the electrical supply to the furnace. b. Be sure the furnace On-Off switch is in the

“ON” position.

c. Defective thermostat circuit - white and red thermostat low voltage leads (M1M*, M1B* models). If the burner motor or combustion fan runs, check:

•Thermostat connections

•Thermostat

d.No voltage to control module - determine if 24 volts (or 120 volts) is available to the control module. If voltage is not available check for:

•Blown fuse, defective transformer, circuit breaker, no electrical supply.

•Limit switch open.

•Loose connections.

Combustion Blower Does Run - No Flame a. Defective centrifugal switch (M1B* Model).

•Check the operation of centrifugal switch by removing end bell of the burner motor.

•Clean contacts of motor.

•If the contacts are closed, replace the motor.

b.Defective pressure switch (M1M* and M1G* 077, 090 Models) - check air tube and elec- trical connections.

c.Burner in purge mode - allow 75 seconds for flame establishing period.

d.Check for proper electrical connections at purge timer, control box, or gas valve.

e.Check for gas supply - gas line valve on, control lever on.

Control Module Is Powered—

Ignitor Does Not Heat Up

a. Disconnect ignitor leads at AMP receptacle and check for 120 volts at the plug during ignition sequence.

b. Replace ignition control if 120 volts is not available at AMP plug during ignition se- quence.

120 Volts Is Available At AMP Plug— Ignitor Does Not Heat Up

a. Disconnect power to the furnace.

b. 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.

c.Check for continuity from ignitor receptacle to burner.

Main Flame Ignites—

Burner Locks Out

a. Ignition control is not properly grounded. b. Defective ignition control.

c. Improper polarity of 120 volt power supply. d. Ignitor has hairline crack.

e. Improper gas pressure or burner air adjust- ment is not allowing flame to contact ignitor tip for flame rectification.

f. Misaligned ignitor does not allow flame to contact ignitor tip for flame rectification.

Burner Short Cycling —-

Thermostat Calls for Heat, Limit Switches Closed

a. Check for polarity. b. Check ground. c. Check flue.

d. Check combustion air. e. Check gas pressure. f. Check orifice.

g. Check the position of ignitor, a normal read- ing should be 40-75 ohms.

24 Volts Supplied To Gas Valve During

Ignition —

No Main Gas Flow

a. Gas valve may be defective. Replace if necessary.

b. Gas piping may be plugged. Check for adequate gas supply to gas valve at union.

Burner Operates—

Insufficient Heat

a. Check thermostat for proper setting and location. Thermostat should not be located where it will be affected by another heat source.

b. Check for clean filter and proper air flow. c. Check burner for proper gas firing rate. d. Be sure unit is not undersized for its thermal

load.

e. Check thermostat anticipator. The nominal anticipator setting is 0.4.

Burner Flame Without Motor Running

a. Gas valve stuck open, check gas valve for proper operation (replace if necessary) and inspect heat exchanger.

b.Check for 115 volts to the combustion blower motor; replace if necessary.

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