# Heil Error: Flame sensed out of sequence



## HeilProblem (Aug 17, 2017)

I have a Heil H9MPT100J16C1 furnace with a Honeywell VR8205Q2795 gas valve. This is controlled by a Honeywell VisionPRO IAQ TH9421C1004A that also controls an air exchanger/humidifer/outside thermostat/etc. About week or so ago I noticed that while the thermostat was set to off the blower would turn on, run for a few seconds and turn off, then on again. The board is flashing an error code 5 "Flame sensed out of sequence". I was then able to tell that once the blower turns on a few seconds later the inducer motor turns on also. This is happening with the thermostat in off-A/C-or completely disconnected from the furnace. Motherboard has been replaced, and limit/roll out switches, igniter, flame sensor have been swapped with a second furnace. This occurs with or without thermostat attached, with or without gas valve unplugged. Im at a loss as to what is causing the blower to turn on and then the inducer to turn on when there is no signal being provided to the unit. Thanks for the help.


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## supers05 (May 23, 2015)

This is normal behaviour if the furnace senses flame when it's not supposed to. (ie. When there's no call for heat.) It'll turn in the fan and inducer to prevent the furnace from melting down. 

It can sense this if:
A) there actually is a flame and the gas valve has failed open.... Very bad news. 
B) The sensing circuit is defective. 

I suspect that it's B, and you'll need to change the gas valve. That's a smart gas valve, so the main control board actually doesn't deal with ignition and monitoring. The original main board probably had nothing wrong with it. 

Cheers!


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## HeilProblem (Aug 17, 2017)

supers05,

The only time there is flame is if I set to heat, then the furnace seems to run normal.

From your explanation I would agree that the sensing circuit could be defective. Just to clarify, this error occurs with and without the valve plugged in.

I would also agree that the old board is probably fine as none of the symptoms changed.


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## supers05 (May 23, 2015)

There's 2 plugs on it. One for power, and the other for control. If you unplug it, you wouldn't have any flash codes at all, unless you mean that you only unplugged the control harness. 

Cheers!


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## HeilProblem (Aug 17, 2017)

supers05 said:


> There's 2 plugs on it. One for power, and the other for control. If you unplug it, you wouldn't have any flash codes at all, unless you mean that you only unplugged the control harness.
> 
> Cheers!


There is a small 2 wire plug(both black) and a larger 3 wire plug(Blue, Brown, Green/Yellow). Regardless of both plugged in, unplugged or in any combination the blower and inducer continue to short cycle and flash the "5" error code.


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## yuri (Nov 29, 2008)

Does not look like a Smartvalve to me as they all have SV95xxxx numbers. Looks like a standard 24 volt redundant valve and is on the Honeywell site.

You should have a flamer sensor and it has a wire going to the circuit board. If that wire is bare and shorted to ground somewhere then it thinks there is a signal. That is why it checks for that B4 starting the main burner.

Or the board is giving you a false code. Carefully check the wire B4 changing the board.

https://customer.honeywell.com/en-U....9.2&IsDlg=1&iframe=true&width=700&height=580


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## supers05 (May 23, 2015)

yuri said:


> Does not look like a Smartvalve to me as they all have SV95xxxx numbers. Looks like a standard 24 volt redundant valve and is on the Honeywell site.
> 
> You should have a flamer sensor and it has a wire going to the circuit board. If that wire is bare and shorted to ground somewhere then it thinks there is a signal. That is why it checks for that B4 starting the main burner.
> 
> ...


Indeed. I think that I ended up with the wrong heil manual. It showed a smart valve. That part number definitely looks like a regular valve

Cheers!


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## HeilProblem (Aug 17, 2017)

yuri said:


> You should have a flamer sensor and it has a wire going to the circuit board. If that wire is bare and shorted to ground somewhere then it thinks there is a signal. That is why it checks for that B4 starting the main burner.
> 
> Or the board is giving you a false code. Carefully check the wire B4 changing the board.
> 
> https://customer.honeywell.com/en-U....9.2&IsDlg=1&iframe=true&width=700&height=580


There is a single wire from the flame sensor to a 12 pin connector at the board. This wire doesn't appear damaged and both the sensor and board have been replaced.

The blower turning on, the inducer kicking on and flashing the error happen regardless of set to A/C, set to off, or controls completely disconnected at the board.


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## yuri (Nov 29, 2008)

You may have to cut it a few inches away from the board. If it stops then the wire is shorted further down the line or the sensor is grounded. You can then splice and reconnect the wire with wire nuts and it won't mind.

Maker sure the sensor is not touching the burner or ground or the porcelain for it is cracked.

Where did you get the board. EBay? Lots of those are used and no good. If it was in a sealed box and bag it should be OK. If not it may be bad.

You cannot run it with disconnected controls as it checks some of them for open circuits etc and may get confused. The board does a self check at startup and checks the limits and circuits for proper positioning etc.


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## HeilProblem (Aug 17, 2017)

First off thank you for all of the help.

I haven't cut the wire but did check for continuity, resistance and short.

The sensor is not touching ground or burner. Porcelain is not cracked. I have swapped with another sensor with no change. The sensor mount is grounded but still isolated with the porcelain.

The board came from a local supply house. It was in a sealed bag and box.

What I was trying to say by disconnected controls is even if I disconnect the thermostat, the blower and inducer still turn on. Showing that the thermostat or vision pro interface isn't the issue.


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## supers05 (May 23, 2015)

This isn't a symptom of the thermostat, so don't worry about it. 

Check your ground and neutral wire. Make sure that they are securely connected and not swapped. Check all the way back to the main panel if you have to. 

Cheers!


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## HeilProblem (Aug 17, 2017)

Sounds good, I'll check back to the panel today. Seems very strange to me that this has ran fine for 10 years and none of the wiring has been touched. Its also very intermittent as far as will be fine for a week then cycle multiple times in a minute.


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## yuri (Nov 29, 2008)

Yeah, check the polarity of the wiring.

Newer high end furnaces have a code for that.

Check the incoming voltage when it is acting up.

Check all your high voltage wiring connections and if you have aluminum wiring then redo them. That can mess up a circuit board when they come loose.


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## mastroj187 (Feb 23, 2018)

HeilProblem did you ever resolve your issue? I'm having the same exact problem on my Heil Furnace. I noticed that it does not happen during the cold months but rather when the weather warms up and the temperature in my basement, where my furnace is located, rises above say 50 deg. F.


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## supers05 (May 23, 2015)

mastroj187 said:


> HeilProblem did you ever resolve your issue? I'm having the same exact problem on my Heil Furnace. I noticed that it does not happen during the cold months but rather when the weather warms up and the temperature in my basement, where my furnace is located, rises above say 50 deg. F.


Next time, you'll want to start your own thread. One of the admins will be a along slowly to help out. 

Do you have the same error code? Have you tried any of the suggestions in the thread? 

Cheers!


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## mastroj187 (Feb 23, 2018)

I am having the same error code (5 flashes) 'Flamed sensed out of sequence' 

I have tried unplugging the thermostat and control valve with no luck. Before I start throwing parts at it I was hoping HeilProblem found a solution since our issue sound very similar.


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## supers05 (May 23, 2015)

mastroj187 said:


> I am having the same error code (5 flashes) 'Flamed sensed out of sequence'
> 
> I have tried unplugging the thermostat and control valve with no luck. Before I start throwing parts at it I was hoping HeilProblem found a solution since our issue sound very similar.


Furnances aren't simple, so his fix is not nearly as likely to help you as you'd think. Each problem is treated independently here. 

Have you disconnected the flame sensor? Checked the polarity of the supply lines? 

The next really important question is what is your model number. 

Cheers!


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