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Discussion Starter · #1 · (Edited)
Hello Fellow DIY'ers.


I am having a problem with my Lennox Furnace. It works fine most of the time but every now and then it won't run when the thermostat tells it to. Turning the power off to the furnace for a second or two then back on again makes it run every time.

I've tried looking at the 2 diagnostic lights after a failure to fire up and it usually indicates a couple of items to check (of which I have no idea what I'm looking for - but am VERY handy and quick learner)

Indicator symptom 1: slow flash - both LED's - alternating
Indicator symptom 2: left LED (OFF) - slow flash right LED

As is typical unit has just finished warranty coverage.
Can anyone please advise on how to track down and resolve this issue. Where I should even begin to start ?

Unit is M/N: 90UGFA3-75-6
LENNOX ELITE SERIES (approx 4 yrs old).



Your wisdom is greatly appreciated - as soon as possilble.
Thanks
Deo.
 

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Discussion Starter · #3 ·
Sorry I have zero years...

Hello Ace,

Thanks for the RTFM advice. Have looked at the diagnostic sheet on pasted to the front of the unit - my issue is not sure what the varying parts it's asking me to troubleshoot are. (The Manual doesn't quite detail this out).

As this is a DIY post and you seem to be quite wise was looking to your vast years of wisdom for advice - not condemnation.

The units was serviced late last year due to a leak in one of the vent pipes causing CO2 to leak into my home with my young family in it. The unit was installed by a professional contractor who services all the homes in our area. when this new home was built (not fly by night as you are assuming) and nor did a get a "great deal" on it.

From your previous posts I thought you would have been a great resource to have help guide the rest of us not in the business to alleviate the costs of these high price "check-ups" - if your advice is to simply call and have it serviced then that's all you had to say.

Thanks anyway.
 

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Hi WyleeCoyote

We are a Lennox as well as a Carrier dealer. The first code you gave was a low voltage or ignitor failure. Now you are getting ready to find out why me and my techs hate Lennox furnaces. There is a 9 pin square moldex plug on the board of this furnace. This plug has the limit and hot surface ignitor circuits in it. Sometimes you can pull this plug off and blow all the crud out of it and get it to work again. Most of the time Lennox furnaces of this vintage came out of the factory with one if not more of the wires not seated in the plug. The first thing I would like for you to do is to shut the power off to the furnace. Locate the 9 pin plug, push all wires one at a time towards the board into the plug. You will probably find that one of them is not seated. If you find one not seated you have fixed your problem. At this point you can plug your furnace back in and see if it runs ok. If they are all seated, chances are your sure light board has a loose socket on the 9 pin connector. Hope this helps.

Good luck
Rusty
 

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Hello Ace,

Thanks for the RTFM advice. Have looked at the diagnostic sheet on pasted to the front of the unit - my issue is not sure what the varying parts it's asking me to troubleshoot are. (The Manual doesn't quite detail this out).

As this is a DIY post and you seem to be quite wise was looking to your vast years of wisdom for advice - not condemnation.

The units was serviced late last year due to a leak in one of the vent pipes causing CO2 to leak into my home with my young family in it. The unit was installed by a professional contractor who services all the homes in our area. when this new home was built (not fly by night as you are assuming) and nor did a get a "great deal" on it.

From your previous posts I thought you would have been a great resource to have help guide the rest of us not in the business to alleviate the costs of these high price "check-ups" - if your advice is to simply call and have it serviced then that's all you had to say.

Thanks anyway.
Lennox units are among some of the best made anywere...there quality control is unmatched by any other manufacture. The fact is that all furnaces made in this era break down, if its that close to the "warrenty date" Lennox will strech the dates to accomadate you, or even the installing contractor may do it. I am a lennox dealer.....i sell and install nothing but the best.
 

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Discussion Starter · #6 · (Edited)
Reseat of Plug did not resolve.

Hello Ace/Carrierman - thank you both for your replies.

Carrierman - did as you suggested and reseat the molex plug located on the SureStart board. Even took 1 step further and reseat ALL wires inside the furnace 1 at a time without resolving the issue.

Of note - the plug you mentioned oddly enough did not have a wire in location #9 (as labelled on the plug). Wire locations and colors as follows:

Pin#1 - Blue
Pin#2 - Yellow
Pin#3 - Brown
Pin#4 - Orange
Pin#5 - Purple
Pin#6 - Blue
Pin#8 - Brown

Not sure if this is a standards thing or not as this is a Canadian furnace just wanted to ensure you had all the info.

SureStart board is a White Rogers (50A62-121-06). Of note from time to time the furnace does actually kick in but is intermittent and cycles for approx 5 min at at time. Thermostat is brand new Honeywell programmable (set on HOLD pattern for now) to 23.5 Celsius and operational as it is sending signal to unit - as noted.

Seems like now there is no ignition on the burners - it tries 3 times then goes into WatchGuard mode. Tried to reset w/ power switch but furnace not firing up. When it does fire up and work the status light go into the alternating slow flash. (Runs for approx 5 imin) What is our next step?
 

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Thoroughbred Mopar Man
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Hi WyleeCoyote

It sounds like the molex plug on the board has a loose pin. The only way to repair it is to replace the board. The replacement board is 97L48 if you decide to replace it. Some of the Sure Lights had a five year warranty on them. Check with your local dealer and they can let you know.

Good luck
Rusty
 

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Discussion Starter · #9 ·
Hello Ace,

With your assistance I'm willing to try. Assuming you mean test the resistance across the ignitor - Sorry for my ignorance but assuming the ignitor in this system is located behind the shiny box where the burners are - what wires to do I test ?

Here is pic of furnace setup that will help me. If you could tell me where to to check that would be great. Thanks.
 

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Discussion Starter · #10 · (Edited)
New Finding

Hello Ace/Carrierman,

Further digging found that there is water in the system cauing the unit not to fire up. Tried draining some water out of the pipe that comes in to the fan - but when the blower initially fires up you can hear water in the motor area. There is a blockage somewhere and I need to find 1) blockage toclear it up 2) Get all the water out of the motor area (black turbine thing in the top section of furnace)

Also - as followup Carrierman- you were correct - the board does have a 5 yr replacement. The 3rd/4th digit of the s/n of the unit indicate the manufacture date (in my case 01) home bought May 01. Alas all was not lost - Got on the line with a great Tech that was willing to help troubleshoot with me on phone leading me upto "drain" issues and further isolate/negate listing of code symptoms on unit.

You guys have been great! Keep up the great help.
 

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Discussion Starter · #12 ·
Some Success!

Hello Ace/Carrierman,

Just quickupdate. Drained most of water out of system and functioning without shutting down. Temp now being maintained. My next steps will be to remove/drain inducer moter and clean all condensing lines and orafaces to ensure smooth operation.

I cannot explain the great feeling it is getting the right help in such a timely manner as you've been generous enough to offer.

Will keep you in the loop once we've given her the final once over.

If you think of anything else I should look for pls feel free to advise.:thumbup:
 

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Hi WyleeCoyote

Just wanted to say excellent, glad you were able to get furnace going. I had not thought of going that way yet. That was my next step though.

Good luck
Rusty
 

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Discussion Starter · #15 ·
Hello ibwahooka,

Once the cover of the furnace was off found a black plastic hose (approx 1" in diameter) - followed the hose upto either end and just pulled it off and extended it vertically away from all electrical and emptied it into a pail. Repeated this for BOTH ends.

Of note - if you hear a "gurgling" sound when blower first fires up you may need to also remove the blower fan (approx 4 screws) assembly and just hold it upside down to drain water from it also.

To this day - all is good to go and am very happy guy thanks to the help from some super guys in this thread. Best of luck!
:thumbsup:
 

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Thanks

Thanks Wylee, your post at "03-01-2007 04:09 AM" was exactly what I needed to fix my furnace. I have the exact same model as yours, from what I can see in the picture. The error lights you indicated "no left light, slow flashing right light", can indicate a problem with the pressure switch, a clogged condensate line, or that the intake/exhaust is clogged. This was explained on the front panel on my furnace, which has a legend of status codes. In this case, your problem (and mine) was a clogged condensate line.

In this case, I could hear water in what I believe is referred to as a "draft induction motor" which is a small blower to supply air for the combustion chamber I believe... anyways I could hear water gushing around in there when the furnace kicked in, and no flame would light (visible in that box on the top), I also had the same status lights blinking at me.

I removed the black hose, from the upper left area that kinda looks like a black funnel, anyways the hose easily pulls from that, and water gushed out. Luckily I had a towel underneath but I was NOT prepared for the amount of water that came out, should have had 2 towels or a bucket or something... anyways the hose was easily removed, I blew in one end and realised right away that this hose must be clogged, because almost nothing came out the other end and I had to blow hard.... anyways I blew really hard while massaging the rubber host and all this black soot/silt came out, i kept massaging the hose and blowing through one end and I got it all out, ran some clean water through it to make sure.

I then had to remove the 4 screws attaching that draft inducer motor to the furnace housing, remove the hose clamp that attaches it to the upper left area of the service opening. I removed the motor with the wiring still attached (no need to remove it), flipped it upside down to get the water out of it.... i reattached the draft inducer motor to the furnace, hooked back up the hose clamp....

Turned the power back onto the furnace, and it's been working since!

Saved me at least a $200 bill to get someone out here to repair it on a weekend...

So thanks again for your excellent advice regarding that black hose and flipping the motor over to clear the water out..... I called the repair guy back and he said "yeah that's frequently what happens but we can't tell people that because then we'd be liable in case something happened..."

This is a really simple repair, and I wouldn't pay anybody to do this because you can do this yourself.
 

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Thanks Wylee, your post at "03-01-2007 04:09 AM" was exactly what I needed to fix my furnace. I have the exact same model as yours, from what I can see in the picture. The error lights you indicated "no left light, slow flashing right" light, can indicate a problem with the pressure switch, a clogged condensate line, or that the intake/exhaust is clogged. This was explained on the front panel on my furnace, which has a legend of status codes.

In this case, I could hear water in what I believe is referred to as a "draft induction motor" which is a small blower to supply air for the combustion chamber I believe... anyways I could hear water gushing around in there when the furnace kicked in, and no flame would light (visible in that box on the top), I also had the same status lights blinking at me.

I removed the black hose, from the upper left area that kinda looks like a black funnel, anyways the hose easily pulls from that, and water gushed out. Luckily I had a towel underneath but I was NOT prepared for the amount of water that came out, should have had 2 towels or a bucket or something... anyways the hose was easily removed, I blew in one end and realised right away that this hose must be clogged, because almost nothing came out the other end and I had to blow hard.... anyways I blew really hard while massaging the rubber host and all this black soot/silt came out, i kept massaging the hose and blowing through one end and I got it all out, ran some clean water through it to make sure.

I then had to remove the 4 screws attaching that draft inducer motor to the furnace housing, remove the hose clamp that attaches it to the upper left area of the service opening. I removed the motor with the wiring still attached (no need to remove it), flipped it upside down to get the water out of it.... i reattached the draft inducer motor to the furnace, hooked back up the hose clamp....

Turned the power back onto the furnace, and it's been working since!

Saved me at least a $200 bill to get someone out here to repair it on a weekend...

So thanks again for your excellent advice regarding that block hose and flipping the motor over to clear the water out..... I called the repair guy back and he said "yeah that's frequently what happens but we can't tell people that because then we'd be liable in case something happened..."

This is a really simple repair, and I wouldn't pay anybody to do this because you can do this yourself.

The gasket behind the ID motor is not meant to be re-used.....there is a pretty good chance you created a problem by fixing another.
 

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lol

where can I get a new gasket then? I'm pretty sure this is a Lennox G26 furnace and in the literature the gasket appears to be listed as the "combustion air orifice" which fits between the "combustion air inducer" and the "cold header collection box"

I mean, I havent noticed any issues since performing the mentioned repair, but if you say I need a new gasket I believe you... where do I find one?
 
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