[CWIZZZZ]

Hello,

Trying to get some advice with the old Lennox Pulse G14 that came with the house I just purchased. Most local professionals don’t really like to work on them anymore so its kinda up to me at this point. I know this is an old furnace and people recommend moving on from them at this point but when it fires up its heats the house up super nice. I feel confident its safe. We have CO sensors in every room. I don't smell any gas around unit pretty sure there's no leaks in the heat exchanger. I wanna see if I can get as much life out of it as possible while i save for a newer model plus the A/C unit that is connected to it works just fine.

The thing works but not without some assistance as I'll get to in the next paragraph. I thought it was a spark plug or ignition control issue so i replaced both along with a new ignition cable. While I was at it I put in a new flapper diaphragm and gasket. New air filter. New smart thermostat in house. Drained the condensation trap. I shined a flashlight down the exhaust and intake tubes. Looks like theres no obstructions as far as I can look.

Nothing I did made it fire up consistently.. But as of recently I found a weird lil trick that makes it fire up first try and for the most part run on auto for the rest of the day. The trick is when the ignition sequence is in its phase where its sending a signal to the spark plug to ignite I turn the gas valve knob to OFF and it ignites and runs. Once I hear that sweet sound then I switch the knob back to ON and its in business doing its thing.

I have no idea what this means and why this gets it to start up first thing in the morning. It leads me to believe theres something with the gas pressure or the valve isn't working the way it should.. Is there anyone out there that knows what I need to do to get this thing to fire up without my assistance and this gas knob trick? I don't want this to become part of my normal morning routine haha.

 

[spitz1234]

Has the heat exchanger been pressure tested. If the x-changer is ok I would start with a tune up. Flapper valves and spark plugs. I would run a analyzer. Has the ignition module ever been replaced.

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[spitz1234]

I would start saving my pennies for a new furnace. When did they stop production? 1997?

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[CWIZZZZ]

I would start saving my pennies for a new furnace. When did they stop production? 1997?

Sent from my SM-G960U using Tapatalk

Thats the goal. Its old school. Def not trying to keep it too much longer while I save. Its winter tho so we need it to work

 

[CWIZZZZ]

Has the heat exchanger been pressure tested. If the x-changer is ok I would start with a tune up. Flapper valves and spark plugs. I would run a analyzer. Has the ignition module ever been replaced.

Sent from my SM-G960U using Tapatalk

I had a guy check the pressure theres no leaks aka its not losing pressure once the gas enters the system.

As I said above.. New flapper, spark plug, and ignition installed.

 

[roughneck]

You’ll have to start by performing the factory spec heat exchanger pressure test.
Carbon monoxide is CO, not CO2.
Most hardware store CO detectors will not alarm if the furnace is leaking small amounts of carbon monoxide. They will not alarm until 70 PPM is achieved for at least 1 hour continuous.

 

[yuri]

There is a gas flapper downstream of the gas valve. It is obsolete. Probably worn now and not passing gas properly.

There is also a stainless steel orifice where the gas passes after the flapper and goes into the chamber. I have been told it can get partly plugged with crud and then the gas shoots off in a weird direction away from the plug.

I worked on thousands of them right from the day they came out plus my Parents had one I installed.

They are all obsolete where I am as some parts are obsolete.

The orifice issue I never ran into but another tech told me and I heard it elsewhere. The gas flapper may be the issue.

The gas valve is a redundant 2 valve type with 2 internal valves. They have been know to stick closed intermittently.

I got rid of the one in my parents house 7 yrs ago and put in a basic Goodman.

 

[CWIZZZZ]

There is a gas flapper downstream of the gas valve. It is obsolete. Probably worn now and not passing gas properly.

There is also a stainless steel orifice where the gas passes after the flapper and goes into the chamber. I have been told it can get partly plugged with crud and then the gas shoots off in a weird direction away from the plug.

I worked on thousands of them right from the day they came out plus my Parents had one I installed.

They are all obsolete where I am as some parts are obsolete.

The orifice issue I never ran into but another tech told me and I heard it elsewhere. The gas flapper may be the issue.

The gas valve is a redundant 2 valve type with 2 internal valves. They have been know to stick closed intermittently.

I got rid of the one in my parents house 7 yrs ago and put in a basic Goodman.

Hi Yuri,

Thanks for the advice and insight.. I had a feeling about the gas flapper. Haven't taken it apart to check it out yet. The gas valve assembly must be pushing gas through but maybe like you said it sticks and lets too much through so maybe when I turn it off during the ignition sequence its letting just the right amount push through. I've read the ratios of gas and air must be just right in order for it to ignite once it reaches the combustion chamber. Or maybe the gas flapper is worn and letting too much gas through. Either way this knob trick I do gets it to fire everytime. Weird.

Also I'll look into the Goodman. I don't need anything fancy just something I can adapt to the current duct and exhaust set up I have already. Did you have to do heavy modifications to get the Goodman to work where the Lennox used to be?

 

[user_12345a]

Every manufacturer makes a basic furnace - goodman won't be the same quality as trane/lennox/rheem etc. (made from thinner metal)

Though for comfort it's best to at least go for a 2-stage with the same type of blower as the basic units.

These days you're forced to get an energy efficient blower motor - there are two types, one is 100% proprietary and super expensive to replace out of warranty. (but this may change by the end of the warranty period)

------------
New ones are shorter than the pulse and there shouldn't be issues getting the contractor to build a transition.

 

[yuri]

The new furnaces are all 33" high so you need to make a duct adapter for the plenum but it is not hard to replace that furnace.

I put in a basic Goodman as Mom won't stay there forever and they are easy to get generic parts for.

I could have gotten a Lennox but I did the job on the side w/o my boss knowing.

I also put a 2 stage Rheem in my Sister's house and it is very reliable.

If you want the quietest furnace then you buy a Lennox or Trane or more expensive heavier built brand. Goodman make a high end line and also a lot of basic units that home builders like.

 

[ATLMike]

Hope you got your issue resolved... I'm dealing with an ignition issue on my G14Q4-80-20 as well.

Figured I'd replace the complete air diaphragm assembly as well (mine's a little corroded), but I having a little challenge finding the right PN for my unit. Does anybody know whether these assemblies are somewhat interchangeable? I understand that the spacer/washer inside the assembly is model specific, but i don't know if the plates and diaphragm (which look similar to mine) are more generic.

Thanks in advance.