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Ignitor fires early or gas valve turns on too late - no ignition

Here is the sequence I see.

I ask for heat. The combustion exhaust fan comes on. The ignighter glows. As the glow fades, I hear the gas valve clicking open but as if it is too late, it turns off, never firing the burners. I smell a hint of propane at this point.

However, if when I hear the valve kick on I BLOW THE GAS THROUGH, THE BURNERS IGNITE! - and the system stays on until the demand for heat is satisfied. But, next time, If I am not there to blow on it, the system attampts to light 3 x and on the last fail, the house blower fan comes on. I can only turn it off by cutting current to the unit. This also re-sets the unit to go through another 3 cycle attempt to fire.

It is as if the igniter and the gas valve are no longer in synck.

The error code is 2 flashes - system lockout (no flame) check line polarity.

Again, if I blow the gas to the fading glow of the igniter, the unit fires and continues to work just fine so I guess all the limiters and safery circuits are functional

The unit worked fine for years. Then a few times, we just turned the power off and it fired the next time. Now it seems the delay got worse.

Is there a way to re-set the cirquit board? any suggestions or revelations on what is wrong? Any questions to clarify my problem? Please ask. I have a multi-tester and can read wiring diagrams and usually manage to fix things myself. This time I need help. Thank you in advance for providing it.

Roadskiman

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  • roadskiman Nov 24, 2008

    The burners were a litle rusty and so the gas did nopt travel well into the ignighter and flame did not light. I took each burner off, cleaned the fins, re-installed and all worked fine.

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Put your hand on the gas valve and see if the click of the valve is opening just before the ignitor goes off if it does your valve is going bad

Posted on Nov 13, 2008

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The unit cycles through all levels and then displays Ignition failure, code B2. I replaced the flame sensor, the ignitor, and there is natural gas at the gas valve.


Sequence of operation for most Gas fired furnaces...
Demand for heat from t-stat
Control board demands combustion chamber purge
(IDM /induced draft motor if it has one)
Control board tests all safeties (this is usually via
the IDM wiring.)
Control board sends 24v to PV at the gas valve igniting
the pilot OR control board sends voltage to the
ignitor as in yours.
Control board sends 24v to MV at the gas valve.
Control board allows time for heat exchanger to warm
then calls for blower operation.

Your sequence of operation? Won't be the flame sensor unless ignion has been achieved. If the ignitor is working/glowing red? Is the IDM working? Make & model#?

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Induction fan comes on ignitor wont ignite


If the igniter turns orange and the gas fires for only a second or two then your heat sensor needs to be cleaned with sand cloth, if it does not turn orange then your igniter needs to be replaced.

Jan 17, 2015 | Amana Gas Furnace 90% Afue 45000 Btu...

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30roof top unit combustion blower comes on but does not ignite ignitors are new


Hi, when the combustion motor comes on, it should or will have a poly type tube on this motor that runs over to a pressure switch. This switch is where the other end of the hose connects. These switches get stuck open at times and have to be broke free by removing one end of the tube and blowing through it. This is a silver looking switch, could be different, but the contact in this switch will stick open causing the unit not to fire up. There is a sequence of operation on these units, 1st the combustion motor will pressurize the box and send pressure to the switch which closes. Once the switch closes, it will send 24 volts to the ignitor module to open the main gas vale to fire the burners. This is just one of several safety switches. This will solve your problem. You can also check this switch by jumping across it with a piece of insulated wire from terminal to terminal. It will fire right up.
Sincerely,
Shastalaker7
A/C, & Heating Contractor

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1 Answer

It does not fire at all times igniter works, I can hear the gas valve when opens, some times it fires for a minute and some times does not fire at all


Problem: Your furnace will not ignite the gas to produce heat for your home. When a furnace has a bad ignitor what I see most of the time is the following sequence of operation:


1. Thermostat calls for heat. 2. Draft inducer motor starts. 3. Pressure switch attached by a small plastic or rubber tube senses the negative pressure produced by the draft inducer and closes. 4. Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound. The ignitor did not glow, the flame sensor (a small metal probe about 1/8" in diameter, with a white porcelain base) does not sense the flame, so after 8 to 10 seconds the hissing sounds stops with no ignition of gas to heat your home. Your furnace shuts down and goes into a lock out condition until you turn your power switch back off and on again. Then the sequence starts all over again with no ignition of the gas. Solution:You probably need to purchase and install a new ignitor. I would suggest that you inspect your ignitor closely for cracks. Make sure you do not touch the ignitor with your bare hands. If you do not visually see a crack, then you could have a furnace control board problem or a limit, rollout switch problem. The furnace's control board might not be supplying the voltage to the ignitor. If your furnace lights and the gas stays on for 8 to 10 seconds, then shuts right back off, then you need to clean your flame sensor with light sand paper or steel wool. You might need a new flame sensor, but most of the time they can be cleaned an will work well after cleaning.

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1 Answer

Looking for sequence of operation for a lennox mid efficient furnace


When there is a Call for heat, the control delays ignition until combustion air

Blower operation has been proved and pre-purge period

Has elapsed. It then opens the gas valve and generates a

Spark to ignite the burners. Trial for ignition lasts for 7 seconds.

At the same time, the control begins monitoring the

Flame sensor. If the flame current is too weak (less than 1

Micro amp) or if the burners do not ignite (within the 7 second

Ignition trial), the control will shut off spark and the combustion

Air blower and de-energize the gas valve. Flame

Current should be between 1 and 5 micro amps to keep the

Gas valve open.

The control will attempt to ignite the burners up to two more

Times. Each time the control restarts the ignition sequence,

It begins with a 45 second pre-purge. If flame is not sensed

After the third trial, the control locks out. Lockout means that

The control shuts off the gas valve, spark and combustion air

Blower for 60 minutes. At the end of 60 minutes the control

Completely resets and will attempt ignition up to three times.

The control can be manually reset before the end of 60 minutes

By momentarily turning off power to the unit.

here is a link to an operations manual

http://0190acd.netsolhost.com/manuals/80MGF_Series.pdf

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1 Answer

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1 Answer

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Check your voltage going into the gas valve. It should be 24-27 volts. If it is to low the gas valve will chatter. If the voltage is strong enough you have a bad gas valve.

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1 Answer

Gas burner will not light. it has a s86c control intermittentpilot 100% shutoff . I HAVE 24 VOLTS AT THE CONTROL COMMING IN BUT NO VOLTAGE TO THE GAS VALVE . NO SPARK AT IGNITOR. PLEASE TELL ME THE...


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1 Answer

Amana


Yes, there is a flame sensor that will tell the gas valve to open, thus igniting the burners. When you say the fan is running is it the blower fan or the little exhaust fan connected to the vent. Because the blower fan should not come on when the burner is not firing. I think you need a new limit switch that or your thermostat is being being unreliable. Try by-passing the thermostat by jumping the red to white wires on it. They are only 24 volts so you need not to worry about being shocked (you may feel a slight tingle if the conditions are right) you do, however need to be careful not to touch any of the wires to anything else as it may blow out your transformer or the fuse protecting it, to see if it changes the problem. When the ignitor is clicking can you see spark jumping from the pilot to the probe? I will need more info to be more helpful.

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