# Lennox Furnace problems



## boolean (Dec 18, 2008)

its a furnace from '97 with a honeywell thermostat bought in 05

no problems until last weekend, when it failed to start heating even when the thermostat has the "heating" display showing. The furnace does start after switching the master switch off/on, then it would heat the home normally for the rest of the day until the morning, im guessing its not starting after a long time of inactivity because I set the period between 12am - 9am to 16C instead of the regular 18C during day time.


I took out the flame sensor yesterday to scrub it clean with sand paper by advice from the net/inspector who couldnt find anything wrong with the furnace since it was working when he came. But it was cold again when i woke up this morning, down to 14C when the thermostat is set to 18C.


anyone know what the problem might be?


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## SKIP4661 (Dec 3, 2008)

Does this furnace have a blue Johnson Control ignition module? This is a box approximately 7" x 3.5", give or take mounted to the firewall. Replaced tons of these controls for the exact problem you have stated. They have bad solder connections on the module board.
If you replace this module replace it with the Honeywell kit. Do not use the Johnson replacement or it will fail again.


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## boolean (Dec 18, 2008)

hey what do you know, it is a johnson ignition controller

G776RGD-11 is the model/serial

you think that's the problem? how do I make sure?


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## SKIP4661 (Dec 3, 2008)

I would just about guarantee that module is the problem. Next time it fails look at the module and see if the green light is on. If the light is on the module is bad.
I am also assuming the furnace is a G20 or G26.


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## boolean (Dec 18, 2008)

so next time (probably tomorrow morning) the house goes cold, if the module's got the green light on, its busted?


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## SKIP4661 (Dec 3, 2008)

If it is the module and you have a G26 90% efficient furnace you will want to replace it with the lennox/honeywell control. If you have a G20 Whisperheat furnace you can use a universal module because you won't need the prepurge feature of the lennox module.


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## boolean (Dec 18, 2008)

its a whisperheat, i'll keep that in mind tomorrow, thanks!


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## boolean (Dec 18, 2008)

alright so the light wasn't on when this morning when it didnt start, does that mean the module is fine?


edit: now the heater wont even heat continuously after power off/on anymore, it just turns on and heats for like 20 minutes or even less, and shut off again


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## SKIP4661 (Dec 3, 2008)

I have seen those modules fail with or without light being on. The light is a sure indication of a failed module. You should replace that module.


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## boolean (Dec 18, 2008)

I replaced the module with a Lennox Honeywell 30w33, all is well now

thanks skip!


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## chrisbatto (Dec 29, 2008)

*Replacing the module in the G20*

Hi Booleen ....Guys,

I am assuming that you received a flame sensor with the 30W33 kit.

If you replaced the flame sensor, can you give me any tips as to the order of operations or what precautions you would take..

I am purchasing the kit tomorrow for the same intermittent problems

Thank

chrisbatto


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## yuri (Nov 29, 2008)

Follow the Lennox instructions and wiring diagram with it VERY carefully. I have replaced lots of them and am a Lennox tech. I would replace the pilot burner also. They warp with old age/get corroded and may be 1/2 the problem. Try Cozyparts.com for Lennox parts. Give them the entire model # and serial # as there are 2 versions of that pilot burner.


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## mfellows (Dec 29, 2008)

I had the same issue with the Johnson Controller last week (in a G26 installed in 1995), the HVAC tech replaced it with a Johnson G776RGD-11 which I think is a used component and I am having the same issues again - can someone confirm that the G776RGD-11 is even manufactured anymore?


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## chrisbatto (Dec 29, 2008)

*New Control Module and Flame Sensor Works Great*

Hi All,

My Dad and I have the same G20 Whisper heat furnaces Both 15 yrs old.

His was really bad, failing to operate 2-3 times daily between Christmas and New Year. We had to turn off the power and restart again otherwise the fan would just run continuously with cold air.

Mine had worked with just a clean up of the flame sensor area last year (brass brush and steel wool) but it had still acted up once since then.

You can't rest at night with these things going on.

I replaced the Module with the Honeywell replacement ( From Amre Supply here in Canada). And a Flame Sensor too. (About $210 total)

I replaced both parts on my Dad's...now working like a Swiss clock and igniting very quickly. 

To have peace of mind, I did mine too. 

I would recommend this to anyone who has an older G20 furnace. My reviews of many websites tells me this is going to be a problem if it hasn't started already.

Yuri and Skip are right and thanks to you. as stated.... MAKE SURE you read the instructions very carefully and completely a few times before you start.... and then read again during the job.... If you don't... you will be in serious trouble.
*
To replace the flame sensor*, you need to remove the cover panel above the damper flap (two small bolt) and you will need to disconnect the small aluminum? gas line from ahead of the Gas valve. I used a Brake line wrench to get even torque. (Shut of the gas at the valve!) 

Then the two small bolts hold the whole thing onto a bracket inside the furnace. So remove these and fish the pipe out to replace the flame sensor in your lap or at a bench...just slides out and back in again.

Be careful of the wire routing and to not lose the grommets where the pipe and wires pass through the cover panel when you reassemble.

Test the gas fitting for leaks (twice if you are like me) by using soapy water and a kids paint brush.

Good luck

Chris


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## mlundquist (Mar 4, 2009)

*fan wire*

I am replacing the lennox g26 johnson control 41k8701 with the honeywell 30e33 and am short one terminal. I have a wire that goes from the fan to the 4th spot on ground. Anyone have any thoughts on where that should go on the new controller? Do I have the wrong replacement part? thanks.


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## msieg (Mar 29, 2009)

*Lennox G26 Flame Sensor - How do I find it?*

Hi all...I see all the posts to clean the flame sensor with steel wool or sandpaper, but how do I find it? Is it in the top or bottom panel? Is it exposed or do I need to remove something else to get to it? I looked at the user manual but it's not "called out" in the drawing...can someone please help? I am not that handy, but I can certainly clean something if I can find it.

I am new to this chat board so I'll look back later or if someone can email me at [email protected]?


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## yuri (Nov 29, 2008)

I am a Lennox tech and it is VERY difficult to get at that sensor. Very good chance you will break it. It is inside the burner box and is twisted in front of one of the burners. I would recommend you get a Lennox tech to do a PM on the furnace and watch him. Next time you may want to DIY. Very important that the drain hose from the exhaust pipe rubber boot be removed and cleaned/flushed with hot water.


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## CutOnce (Mar 28, 2010)

chrisbatto said:


> Hi All,
> 
> My Dad and I have the same G20 Whisper heat furnaces Both 15 yrs old.
> 
> ...


This was the best post i found on any site !! Great job and many thanks !! I am a carpenter and not so mech. inclined..... This whole operation took about 2 hours (for me ) , with cleanup and saftey checks ......... 3 days no Heat --- 2 hours and " WHISPER HEAT " !!!! Very happy and really wanted to say thanks ....Justin

Try out instructions by *chrisbatto in this tread...*


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## jpryma (May 30, 2010)

*Simillar problem with 30W33 module installed*

I purchased a 1993 home last year with the G20 furnace. It has the 30W33 igniter module installed (date unkown). For the past several months, the temperature is irratic. It will not come up to desired temperature. I have replaced the thermostat but this did not solve the issue. 

The furnace ignites, blower starts, then the gas valve solenoid turns off. The blower continues to run, then the burners re-ignites. The furnace cycles through this until it stops all together. I am getting a *6+3 green flash* and a *1 yellow* flash.

I have cleaned the flame sensor as well as tested the microamp values. They both look good. Could it be that the 30W33 module is faulty?


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## jpryma (May 30, 2010)

*Solved!*



jpryma said:


> I purchased a 1993 home last year with the G20 furnace. It has the 30W33 igniter module installed (date unkown). For the past several months, the temperature is irratic. It will not come up to desired temperature. I have replaced the thermostat but this did not solve the issue.
> 
> The furnace ignites, blower starts, then the gas valve solenoid turns off. The blower continues to run, then the burners re-ignites. The furnace cycles through this until it stops all together. I am getting a *6+3 green flash* and a *1 yellow* flash.
> 
> I have cleaned the flame sensor as well as tested the microamp values. They both look good. Could it be that the 30W33 module is faulty?


Turns out that the jet orifice for the pilot light was getting plugged and not heating the sensor enough. I took the jet apart and gently opened the orifice. The sensor now glows red and furnace stays on. Hope this was it.:thumbsup:


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## KeithG (Nov 19, 2012)

*Johnson Controls ignition box repair*

After reading everyone's comments on the Lennox G20 Whisperheat ignition problems, here's my experience. My girlfriend's Whisperheat was going into fault mode about once a day with the start of the heating season last week. It had similar symptoms to those mentioned here: the furnace would stop igniting during a call for heat and would fault with the damper door open, sometimes not even lighting. Sometimes the main gas valve chattered as well when it did light. A reset of the system, by cycling the thermostat or flipping the furnace power switch off and on, would fix it for a while. The thermostat was giving the right signal to the terminal strip on the furnace circuit board. I did the following:

1) Snipped about 1/4" off the high voltage wire coming from the ignition control box to get a better connection on the spike and reinserted.

2) Cleaned flame sensor.

3) Checked to see that the pilot flame was touching the flame sensor.

The furnace was still not lighting reliably. A wiggle test of the spade terminals on the Johnson Controls g776rgd-11 box would consistently cause the main gas flow to cut out or prevent the unit from even lighting--sounded like bad connections in the ignition box, as others have mentioned.

With nothing to lose, I hacked into the Johnson Controls box to check out the solder connections. I drilled out the brass grommets to remove the back panel and removed the circuit board. Everything was covered in conformal coating, which came off with Goof Off and a toothbrush. I could then see the solder joints clearly. It looked like a few were cracked, particularly on the large leads on the two relays. I resoldered those joints, and all the others I felt safe soldering with a 35 W iron with a fairly large tip. I might touch up the surface mount components and microprocessor connections later with a smaller iron I have at home.

Anyway, I put the ignition box back together and in the furnace, and the furnace is working perfectly now. A wiggle test of the spade terminals has no effect on the furnace operating. I'll see how it goes in the next few days but it's looking good for the moment.


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## Marty S. (Oct 31, 2009)

Folks looking this up later...most every G20 has developed cracks in the heat exchanger. They still run but should be red tagged at that point. The heat exchangers had a 20 year warranty,the date code is the third and fourth numbers in the serial number. If you have one it would be a good idea to get it inspected by a good hvac tech.


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