I have an old gas furnace. The thermostat is working but the burner won`t ignite. It`s 40 + years old but has been maintained it`s whole life. A new furnace is not possible at this time.

• What Is Electronic Ignition?

  Jupiterimages/Getty images The electronic ignition system in a gas furnace is a modern development that provides more reliable performance than a standing pilot and offers energy savings through better furnace efficiency. There are two basic types of electronic ignition systems:
  
  • An intermittent pilot system uses an electronically controlled high-voltage electric spark to ignite a pilot light and subsequently the main burners when the thermostat calls for heat.
  • A hot surface ignition system uses an electronically controlled resistance heating element, not unlike a light bulb filament, to ignite the gas burner.
  Understanding some of the basic components of a modern furnace will help you identify the type of furnace you have and narrow down the list of potential problems.
  
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  Types of Electronic Ignition Furnaces

  
  Design Pics/Getty images Most furnaces with electronic ignition are either conventional induced draft furnaces or high-efficiency condensing furnaces.
  Induced draft furnaces use a small fan to draw the combustion gasses from the combustion chamber and out of the house through the flue (chimney). This system is more reliable and safer than old conventional furnaces, which relied on a natural draft coming in from an opening at the front of the furnace. Induced draft furnaces use either an intermittent pilot (IP) or hot surface ignition (HSI) instead of a standing pilot light. The combination of electronic ignition, electronic controls, and artificially created draft improves the efficiency of induced draft furnaces over older conventional models.
  Condensing furnaces use two heat exchangers, where conventional furnaces use only one. After the gas is burned to heat the primary heat exchanger, the secondary heat exchanger draws heat out of the hot exhaust gasses, cooling them to the point that the water vapor in the exhaust condenses into water. The resulting flue gases are so cool they can be vented outside via a plastic (PVC) pipe, while the condensed water is run to a floor drain. Condensing furnaces use hot surface ignition (HSI).
  
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  Troubleshooting an Intermittent Pilot (IP)

  
  Michael Interisano / Design Pics / Getty images Typically found in induced draft furnaces, an intermittent pilot ignites the burner gas with a high-voltage spark only when the thermostat calls for heat. Once the pilot is lit, and the main burner senses the pilot flame (using a flame sensing rod), the main burner ignites. The intermittent pilot flame goes out after the heating cycle and remains off until the next time the thermostat calls for heat.
  The furnace gas valve for this type of furnace is identifiable with its solenoid designations: MV, PV, and PV/MV - where MV = main valve, PV = pilot valve, and PV/MV = common.
  Common problems with IP ignition include:
  
  • Ignition doesn't occur, and the furnace won't go on
  • A spark is present, but the pilot won't light
  • Pilot lights, but the main burner doesn't come on
  • Burners ignite but turn off after a few seconds
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  Troubleshooting a Hot Surface Igniter (HSI)

  The hot surface igniter (HSI) is the most commonly used electronic ignition system. It works like a light bulb filament, heating up when electricity is passed through it. Most are made from silicon nitride or silicon carbide. The igniter is located in the flow of gas entering the burners.
  When the thermostat calls for heat, 24 volts are sent to the electronic ignition control module, which energizes the furnace blower and other systems and sends 120 volts to the HSI. The HSI heats up to around 1,800°F to 2,500°F and glows red-hot. Then the gas valve opens, and the burner gas is ignited by the HSI. Once a proper flame is sensed by the flame sensor, the HSI turns off and stays off until the next heating cycle. In some furnaces, the HSI also serves as a flame sensor (called local sensing) instead of having a separate sensing rod in the burner flame (remote sensing).
  Under normal conditions, an HSI should last for three to five years, and they eventually crack and need to be replaced. This can happen sooner if the oils from your skin get on the element through improper handling. That means: Don't touch the element with your bare hands!
  HSIs usually cost between $25 and $50, and it's a good idea to keep a spare on hand, in case one goes out at night or on the weekend, when you can't easily get a new part.
  Here are some of the common causes of HSI failure:
  
  • Premature failure due to improper handling (oil from skin got onto element)
  • Improper igniter
  • End of normal usage life cycle (keep a replacement on hand)
  • Voltage in the furnace electrical circuit is too high (over 125 VAC)
  • Severely dirty air filter, causing the high-temperature limit switch to cycle the furnace ignition on and off frequently
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  Reading Control Board Codes

  
  Mohd Firdaus Mohd Damanhuri/EyeEm/Getty images Most modern furnaces with electronic ignition systems have an integrated circuit board that controls many sophisticated processes. The boards can perform self-diagnostics and provide failure codes, similar to the diagnostic computer in your car.
  If a failure occurs, LED lights on the control board light up in a blinking pattern to indicate a specific failure code. The codes are listed in a chart in the owner's manual and usually on a door or access panel on the furnace. Control boards are usually located inside the blower compartment of the furnace. If the board has blinking lights, refer to the chart to decipher the code and help identify the problem area with the furnace.

Remove the stat cover and jump out the red and white wires. If the furnace still doesn't come on, it is your t-stat. Replace it.

As I'm sure you already know, Empire Comforts Systems, no longer makes that model heater and hasn't for some years, now. I mentioned that, because if your unit needs parts, they may be almost impossible to get. In any event, there are a several things that may be causing the problem.

• Low Gas Pressure - Burner is not receiving enough gas. Check for obstructions and have gas pressure at the unit checked.
  
• Clogged burner or air intake (venturi valve) is partially clogged. Clean burner ports and venturi valve.
• Gas line Shut Off Valve at heater not fully open. Check Gas line Shut Off Valve.

At 23 years old, you've gotten your money's worth out of this unit and it may be time to replace it. Empire makes several Direct Vent Wall Furnaces that are rated as High Efficiency Furnaces. In the long run, the money saved in fuel cost, would be worth installing a new one.

Hope this helps you solve the problem.

If the burners do not fully ignite, the sensor will shut the furnace down. The lack of sufficient burner flame is a gas valve or gas pressure problem within the valve.
Replacing the gas valve with the original one may get you going. I surely suggest a professional service company for safety reasons and a thorough inspection. A 20 year old furnace is past it's normal life span.

recommend getting a carbon monoxide indictor or having some one test it. with it being over 15 yrs old if checks good replace ignitor assy should fix it ok

If you have a volt ohm meter take the two leads off the gas valve and ohm out the connection should have resistance for the coil. You said you have 12 volts from the thermostat white and red in the heating mode you should have minimum 26 volts. If you want to check the transformer should have 28 volts. Almost sounding like the transformer is getting weak. You can get parts for a 20 year old unit at any HVAC parts house. Try Washer Specialties here in Wichita Kansas they are on the web. Lowes even carries Transformers. Has to be rated 120 volt primary side secondary side 24 volts and 40 VAC.

Hello Bob,
Welcome to fixya,

You said, Amana Air Command 80, 20 years old.
Electronic ignition.
Furnace does not start.
Good power to furnace.
Thermostat properly set.
Where do I start looking?

Sounds like you possibly have one or more bad jets if the unit is a gas furnace!
Let me know how it goes.
Huuum

WOW, listen to this story!
I understand you are looking for the solution to fix your furnace your self.
But I want to tell you my story about my smart wife and our furnace.
When we moved into this house the furnace was 20 years old and she suggested that we put a new one that it will save us money.
I laughed at her and replied if it's not broken why fix it!
Six years later it finally broke down and I replaced the whole furnace and central air unit with a new one.
Our utility bill went down $100 dollars a month!
That's $7200. that I lost over 6 years due to not respecting my wife's power of reasoning!
If you can afford it or can get financing replace any unit 20 years old and it will pay for it self.
Can you imaging $1200. a year for 20 years is $24,000 dollars I'm saving with a new and efficient unit.
Do the math!!!!!!!!!

Thank You,
Huuum, Hope I gave you some good fatherly advice.
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Your hot surface igniter may be bad. It may be cracked which would prevent it from starting the burner flame.

Check the heat anticipator setting on the thermostat if its a mercury type thermostat. It may not match the proper amp draw. Take the cover off and it is a little metal lever. Try different adjustments to see which are better. If its a digital thermostat it may have an internal setting. There are several other possible reasons this could happen but that would be the most likely. for more infor on self diagnosis or the like check out my fave website Ra-Jac Air Conditioners and Heaters TX for repair information.

PS: If its a new installation it should have a one year warantee so call back the person who put it in. If you did it yourself be extremely careful gas furnaces can be dangerous. You might want a service person to check the job out for safety hazards. Good Luck with it.