Arc from the ingition control board?! - gas/AC package unit


  #1  
Old 12-01-23, 04:23 PM
N
Member
Thread Starter
Join Date: Nov 2020
Posts: 24
Upvotes: 0
Received 0 Upvotes on 0 Posts
Arc from the ingition control board?! - gas/AC package unit

20 y/o Lennox gas furnace/central AC outdoor package unit. Please excuse the long story.

On the furnace side, the problem of fully starts (brings in hot air) but shuts off shortly after, has been recurring for quite some time since winter of 2019/2020.

Initially, I tried and succeeded with (comical) quick fixes that, by means of luck and coincidence, that made the furnace going and lasting throughout the winter (ask what the quick fixes are if interested, again, it's pure luck and I don't know why it worked).

I have tried replacing the flame rollout limit switch to no avail.

One major replacement that seemed like a permanent fix was replacing the ignition control board in 02/2021. The furnace ran fine the whole winter of 2021/2022, until 03/2022 when the heat exchanger gave out and I had it replaced in 05/2022.

The winter of 2022/2023 was fine until 03/2023 when the problem became two-fold: fully starts (brings in hot air) but shuts off shortly after, or starts (but only hear the fan running and no hot air) and shuts off shortly after, Of course, if I left the furnace on, it would attempt to restart the cycle. I decided to leave it be since it was near the end of winter, and just resorted to indoor space heaters and wait until warm to get it checked out. However, the furnace went back to acting normal on its own. Again, I don't know why.

In summer 2023 I had a HVAC company come do a checkup and the technician thought the issue could be the flame sensor and advised that if I had the problem again, try replacing that. Of course the problem came back again 2 weeks ago and this time the furnace would not go back to normal on its own. So I installed a replacement flame sensor. However, the unit didn't fully start and this time I observed something unnerving - a visible electric arc from the ignition control board during the seemingly normal starting sequence as the unit makes the quick clicking sound as when trying to ignite the flame. I didn't see clearly which components on the board emitted the arc but I have drawn the location of it on a stock photo of the board attached in the picture below.

Could this be another failed ignition control board? Any other advice?

 
  #2  
Old 12-01-23, 04:50 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,593
Received 3,881 Upvotes on 3,478 Posts
I know money is tight but furnaces require routine servicing.
They are a gas appliance and must be treated as such !
You had a tech there guessing.... call his *ss back.

That black device is a high voltage spark coil.... just like on a car.
If it is visibly arcing.... typically it's bad.

It sounds like you have a high heat shutdown issue, It should show up in the fault LED.
 
  #3  
Old 12-01-23, 05:12 PM
N
Member
Thread Starter
Join Date: Nov 2020
Posts: 24
Upvotes: 0
Received 0 Upvotes on 0 Posts
Hi Pete, thanks for the reply. What should a routine service typically include? I have a hunch that the board is bad, as the light at the center of the board was making a fast blink, and I recall seeing so on the old board when I replaced it back in 2021.

I will go ahead and order a replacement board, and post question to the HVAC company. Would you say the board is at fault for the malfunction of the unit, instead of the flame sensor, or other components?

I will get this unit entirely replaced in time. In fact I had already acquired a new unit (with the newer R410a refrigerant) last summer , but was trying to see how much life I can still get out of the current unit. Like mentioned, cost of putting in such a unit for a single-family residential building is something I must be well prepared for.
 
  #4  
Old 12-01-23, 06:28 PM
R
Member
Join Date: Oct 2016
Posts: 2,183
Received 199 Upvotes on 181 Posts
Heat exchanger needs to be checked asap before any parts are ordered.
If the heat exchanger is cracked or rotted, the heating portion of the unit is dead and can no longer be used. Itís a carbon monoxide and fire hazard to run a unit with a compromised heat exchanger.
This is part of the yearly checkout of the system.
 
  #5  
Old 12-02-23, 12:17 AM
N
Member
Thread Starter
Join Date: Nov 2020
Posts: 24
Upvotes: 0
Received 0 Upvotes on 0 Posts
The heat exchanger was replaced with brand new in 05/2022 after a CO leak in 03/2022. The old exchanger has visible hole(s) in it.

Right now the unit has an ignition control board that's making arc, I will get it replaced first. The board was put in brand new in 02/2021, not sure what could have exasperated its (apparent) failure.

Meanwhile I will contact the HVAC company that came and checked out the unit during summer.

Since the furnace quit working about 2 weeks ago all I can get it to do is blow in cold air then shuts off without ignition and the furnace would try once more, maybe couple more times and still shut off and stays shut off. I could manually reset the thermostat and have it restart the cycle but it's the same pattern. When the furnace had issues in past winters, it would at least start, blow warm air and then shut off.

From what I can find on the internet so far, it seems that shutting off before ignition could be pressure switch, or the igniter that is at fault.

Any further suggestions/prognosis are appreciated.
 
  #6  
Old 12-03-23, 06:27 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,593
Received 3,881 Upvotes on 3,478 Posts
I thought you said the hv coil was arcing.
If the spark is not appearing at the pilot/burner area.... the furnace won't light.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: