Frost Fighter IDH350-ll

Questions and Answers

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Sean MartinezAug 27, 2025
How to fix a Frost Fighter Heater when the main fan won't turn on?
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  gary04Aug 27, 2025
  If the main fan of your Frost Fighter Heater won't come on and the unit shuts down on high limit, check the temperature feeler to make sure it is properly in place. Jumper out the fan switch to test the motor. If you have voltage to the motor and it still does not start, replace the motor. Check the line voltage to ensure proper voltage. Also check the amp draw on the motor; the motor may be running too hot and not run due to thermal overload being tripped. Replace the fan switch if you have power on one side after the unit heats up but it does not make. Replace the high limit, as it may be tripping too soon and not giving the fan switch time to engage. Ensure the fan switch temperature is correct for weather conditions.
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Pam JonesAug 30, 2025
Why does my Frost Fighter IDH350-ll Heater keep cycling on high limit?
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  Stephanie SmithAug 30, 2025
  If your Frost Fighter Heater is on but cycles on high limit, check the air flow to ensure both ducts are in place, clear of obstructions, and straight. Check the pump pressure, as the unit could be over firing. Verify that the proper size of nozzle is installed. You may need to change the high limit. Note that the maximum duct length with a 2 x 12” outlet is 24’ on each side, and with a 1 x 16” outlet, the length is 45’. Any longer will create back pressure in the unit and trip the high limit. Using #2 fuel type will increase BTU output @ cold ambient temperatures, resulting in overheating.
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victoriaallenSep 1, 2025
Why is the combustion chamber of my Frost Fighter IDH350-ll turning red?
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  amy47Sep 1, 2025
  If the combustion chamber of your Frost Fighter Heater turns red, the nozzle may be firing sideways, in which case you should replace or adjust it. The nozzle could also be clogged, requiring replacement. Ensure the temperature feeler is properly in place or not missing; it must be touching the heat exchanger. The high limit may not be functioning, requiring replacement. Excessive pump pressure could be the cause; check and reset if necessary. Consider the fuel type and refer to recommended settings.
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Tiffany CruzSep 3, 2025
What to do if my Frost Fighter Heater burner fires then locks out?
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  Joshua WoodsSep 3, 2025
  If your Frost Fighter Heater burner fires and then locks out, several issues could be the cause. First, check the oil pressure to ensure the solenoid valve is opening. The nozzle should be checked to ensure it is clean and emitting a good spray pattern. The cad cell (flame detector) could be defective, or the wires between the cad cell and primary control could be pinched or crimped. Prime the fuel pump by loosening the bleeder screw until a steady stream of fuel comes out. Also, check the polarity, ground, and voltage (must be between 108-132v AC), and make sure the high limit is functioning properly. If the unit locks out three times in succession, it will go into restricted lock out mode; to reset, hold down the reset button for 45 seconds until the LED flashes twice.
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Evan WhiteSep 5, 2025
Why does my Frost Fighter IDH350-ll Heater cycle on high limit?
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  Sara GarzaSep 5, 2025
  If your Frost Fighter Heater cycles on the high limit, check the air flow to ensure both ducts are in place and clear of obstructions. Check the pump pressure, as the unit could be over firing. Verify that the proper size nozzle is installed. Consider changing the high limit. Note that the maximum duct length with a 2 x 12” outlet is 24’ on each side, and with a 1 x 16” outlet, the length is 45’. Using #2 fuel can increase BTU output at cold ambient temperatures, resulting in overheating.
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John HallSep 7, 2025
What to do if the burner motor starts but my Frost Fighter Heater won't fire?
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  fboydSep 7, 2025
  If the burner motor starts but your Frost Fighter Heater will not fire, check for power on the blue wire on the primary control going to the ignitor. Remove the electrode assembly and check the isolators for cracks or chips in the porcelain. The nozzle should be checked and ensure it is not clogged or blocked. Ensure the air shutters are properly set to factory specifications. Check for power on the violet line on the primary control. Remove the copper fuel line at the electrode assembly to ensure fuel is coming out. At the bleeder screw, check for proper out pump pressure. Check the oil filter, oil pickup tube, and oil lines to ensure free flow and that they are not clogged or dirty. Check electrical polarity and grounding.
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Andrew VaughnSep 9, 2025
How to fix a smoky fire in my Frost Fighter IDH350-ll?
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  barbaramcdonaldSep 9, 2025
  To address a smoky fire in your Frost Fighter Heater, begin by checking the nozzle to ensure it is tight and not clogged. Inspect the combustion chamber for cracks or burnt-out sections. Verify the air band settings and check the pump pressure. Ensure the slide plate is in the correct position. Also, check the recommended settings if you are using #2 fuel in cold ambient temperatures.
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teresa46Sep 12, 2025
Why is the combustion chamber turning red in my Frost Fighter Heater?
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  jenniferalvarezSep 12, 2025
  If the combustion chamber in your Frost Fighter Heater is turning red, the nozzle may be firing sideways, so replace or adjust it. The nozzle could also be clogged, requiring replacement. Ensure the temperature feeler is properly positioned or not missing; it must be touching the heat exchanger. The high limit may not be functioning and might need replacement. Check for excessive pump pressure and reset it if necessary. Refer to page 7 for recommended fuel type settings.
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Andrew AdkinsSep 13, 2025
Why is there a delayed ignition in my Frost Fighter Heater?
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  John ReynoldsSep 13, 2025
  If you're experiencing delayed ignition with your Frost Fighter Heater, start by checking for proper electrode settings. Inspect the isolators for cracks or a conducting coat of soot or oil. Make sure the air shutter is not overly open. Check to ensure the pump pressure is properly set. Try changing the nozzle. Inspect the fuel filter and replace it if necessary. Ensure that draft or wind is not blowing out the flame.
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malikbellSep 16, 2025
What to do if the main fan won't come on and my Frost Fighter IDH350-ll Heater shuts down on high limit?
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  emily97Sep 16, 2025
  If the main fan on your Frost Fighter Heater will not come on and the unit shuts down on the high limit, check the temperature feeler to ensure it is properly in place. Jumper out the fan switch to test the motor. If there is power on one side of the fan switch after the unit heats up but it does not make contact, replace the fan switch. Consider replacing the high limit, as it may be tripping too soon and not giving the fan switch time to engage. Ensure the fan switch temperature is correct for the weather conditions.