Rheem gas furnace pilot lights, but no burners or fan

check thermostat is on and working correctly and check wiring at unit

• 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.

pilot lit on gas furnace, but the burners won't light (Home ...

answers.angieslist.com > Home > HVAC

Oct 26, 2013 - i have a gas furnace with a lit pilot, but the burners won't light. ... if the thermocouple does not sense the heat of the pilot it prevents the gas controller fromturning on the burners. ... clamped onto the outgoing hot water pipe, if huydronic system) that is telling the furnace it is too hot, whether or not that is true.

Mots the t stat or gas valve check connections first most likely it's the gas valve cause the furnace is old valve is stuck cannot open

Troubleshoot an ignition problem on a Lennox gas furnace ...

? 2:44
https://www.youtube.com/watch?v=yXIxgzwMkPs
Nov 17, 2012 - Uploaded by grayfurnaceman
This furnace should light its pilot with a spark then the pilot proves its on ... Troubleshoot an ignition problem on a Lennox gasfurnace .... Pilot and no inducer but is the same model as that great video! ... You probably have dirty burners. ... How do you know spark module is not sending 24 volts to mv and pv ...

Lennox Furnace Model G11Q3-82-2 - RepairClinic.com

If I recall correctly, model number Rheem furnace you listed has electronic ignition to light the pilot, when the home's thermostat calls for heat. Is this what you're having a problem with?

I agree. Either the pilot flame is dirty and is not making good contact to heat up the bi metal strip on the pilot assembly, or the pilot assembly is defective. 90% of the time if you clean the pilot orfice and the pilot burner it will take care of the problem

clean ports where gas comes out for pilot light also check gas pressure (gas company)

There is a thermocouple "wire" that is supposed to be touching the pilot flame.
The thermocouple senses a flame (hot) and allows the heater to operate. If the thermocouple does not sense that the pilot is on, then it will not allow the furnace to operate.
Bend the thermocouple wire (or the pilot tube) so that the pilot flame is touchingg the thermocouple.

That shouls work now.

The air from the fan should not be blowing through the same cxavity that the pilot is in.
If it is, then you may have a leaking furnace whereby carbon monoxide may be seeping into your living quarters.
If the fix above works and the pilot stays on after the heater starts, then there is probably no leak.

Let us know the results ... post a comment or "RATE" this or another expert's solution.

A few years back I helped a neighbor with this same problem in a forced air, gas fired, "horizontal" furnace in his attic.

After having him cycle the thermostat a couple dozen times while I watched through the opening in the side of the furnace, I finally figured out what was happening.

First, there were about 6 cast iron burners [about 14 inches long with two rows of gas holes along the length]. These burners were parallel to each other and oriented perpendicular to the long axis of the furnace.

The gas was fed to the ends of the burners with a pipe manifold. The standing pilot light was at the center between burners 3 and 4. Due to the spacing distance between the burners, the pilot light was too far from even burners 3 and 4, the flame could not "jump" to ignite them, or any of the other burners. The manufacturer had installed a thin sheet metal "tent" which ran from the gas entrance end of burner 1 to burner 6, and was about 2 inches above the burner, AND the pilot light.

The standing pilot was on all the time. When the gas control valve turned on, gas began to come out of all the burners at the same time. Naturally it came out of the gas supply manifold ends of all the burners.

The "tent" captured that gas coming from the burners and "filled" up to over the pilot light which ignited the gas at that point, and the flame would propagate along the tent to ignite the gas coming out of all of the burners.

In my neighbors case, the tent had somehow become dislodged so that it did not cover all of the burner ends. For those burners which it did cover [including the pilot light] it caused the burners to light properly.

For those burners who's ends were not covered, and who's gas could not be captured, they would NOT ignite simultaneously with the others.

As these burners WERE feeding gas into the combustion chamber, the gas "envelope" would spread until it reached the nearest flame ignition source, at which time the entire "bubble" of gas would ignite with a minor boom [actually a low energy explosion]. Flame would momentarily shoot out of the burner chamber opening, and from that point the furnace would operate normally until the next restart cycle.

Although there could be several causes, I suspect that the symptoms you describe are the result of DELAYED IGNITION of some or all of the main burners.

IF this is the problem, then the solution is to clean all the burners [including the burner outlet holes in the ignition ends of the burners], clean out the burner compartment, AND properly adjust the orientation of whatever system [you have to evaluate how it works from analysis of YOUR furnace] your furnace has to ensure all burners ignite as close to the same time as possible.

When operating properly, the ignition should be a smooth transition, burner by burner, from the pilot to the farthest burners. In other words. the ignition will "flow" from the pilot outward to each adjacent burner until the farthermost ends ignite last. This usually doesn't take more than one or two seconds at the most.

Unless you are an experienced handyman, and understand this analysis and instructions, I strongly suggest that you engage the services of a professional furnace technician.