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Regan Land
Regan Land, HVAC Technician
Category: HVAC
Satisfied Customers: 582
Experience:  18 years of experience, NATE Certified, Licensed HVAC Contractor, Certified IAQ Specialist
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lennox 80uhg3/4-100a-2 surefire board - 2 alternate fast

Customer Question

lennox 80uhg3/4-100a-2

surefire board - 2 alternate fast flashing leds

checked all conditions in service manual

heater does not start
Submitted: 7 years ago.
Category: HVAC
Expert:  Charles replied 7 years ago.


maybe I can help


The flashing led is a error code if you look on the inside of the access panels one may have a schematic with the diagnostic codes listed on a chart that will tell you what the code means. like pressure switch failure, or maybe ignition failure, Flame sense failure and so on there will be more codes than that those are just a few of what they might be.


If not describe just what it does and doesn't do besides light do and I will try to help you


for example does the combustion/ inducer fan start does the igniter glow/spark and so on. the more you tell me the better I can help.


if I can help you further let me know

Edited by Charles on 3/17/2010 at 8:39 AM EST
Expert:  BillyHvac replied 7 years ago.


Page 7 here gives broken ignitor as a possible cause of alternate fast flashing.


The ignitor is the most common part to fail. Check the ignitor first and go from there.


See page 7 here -


Customer: replied 7 years ago.
The ignitor measures 15 ohms which is within the 10-19 ohm range. The inducer fan does not start and the ignitor does not glow.
Expert:  Charles replied 7 years ago.

It seem's some here Are quick to sell parts without knowing the real problem 1st.


the inducer fan/ combustion air fan has to start 1st.

if it doesnt you need to look at other issues 1st. not the igniter.


Just Like to keep the customers open to the correct way to go about troubleshooting.


Ask questions1st answer after informed without throwing the wrong parts at the problem.


Thank you and if I can assist you further I would be happy too. Please read my signature at the bottom of my post Thank you!!!

Expert:  BillyHvac replied 7 years ago.


The Surelight control board monitors ignition lines, ignitor and ground before pressure switch makes . Thus the recommendation given by Lennox, with that code, is to start with the ignition components.


With the proper service manual, you can make better head way in diagnosing the diagnostic blink code.

Expert:  Charles replied 7 years ago.

Just remember YOU DO NOT have to accept any answer. Until you are satisfied


I was just trying to help you help yourself I could easily throw some documents at you too. But from experience have seen control boards Give false codes when they are the problem and have seen them give no code and the control was still bad. Real world hands on experience. I am a Owner operator Of my Own HVAC company which means I go out in the field daily and make repairs on problems just like this all the time.


But not being there to see for my self I have to rely on good information to make the proper diagnosis. and do not jump to conclusions without all the facts.


I am not saying the control Module Is Bad nor to run out and replace it. Just trying to get Well Informed 1st. Your problem code could be valid. if it is that would make the repair very easy. I hope it is accurate for your sake igniter's are much less expensive than control modules


If you would prefer I will opt out so Billy can lead you on.


Just let me know thank you and have a wonderful day.

Customer: replied 7 years ago.
I pretty sure neither of you will be able to further assist without hands on. Thanks for trying.
Expert:  Charles replied 7 years ago.

Not a problem hope you get your problem solved. and yes hands on is the best way when possible. and affordable


I think you have made a wise choice.


Good luck and have a Nice day.

Expert:  Regan Land replied 7 years ago.

Hello. Welcome to My name is XXXXX XXXXX I'll be happy to assist you today.


The alternating slow flash is a code telling us that the burners failed to ignite. That can be caused by a number of problems including the hot surface igniter. I see you have ohmed it out and it tested good, so we need to look further.


When the board is flashing this code, it is in a 60 minute 'Watchguard' period. We can reset the board by unplugging the furnace and plugging back in.


After doing so, what steps does the furnace go through?