Intermittant ignition problem with Elderly Carrier Furnace

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Old 10-27-20, 05:23 PM
J
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Intermittent ignition problem with Elderly Carrier Furnace

Hi All. My furnace is having an intermittent ignition problem. I've actually been dealing with it for a few years now, but figured maybe this community could help me solve it so I can try to get a few more years out of her.

I came across this old thread which basically describes my problem with 1 minor exception:
https://www.doityourself.com/forum/g...-ignition.html

The exception is that when the furnace is in failure mode, I do not hear a click. I can then make the furnace ignite by wiggling the top wire that connects to the gas valve while the igniter is lit.. then it clicks and ignites.

The problem has caused a few cold mornings, and I've come home to a cold house on occasion, but once the furnace is warmed up and running, it usually doesn't have any trouble staying on all day. Hoping for an easy fix, I re-terminated the wiggle wire, but the problem remains. This leads me to believe the problem lies with the gas valve module. Is the obvious solution simply to replace the gas valve? Or could it be something else (hopefully something simpler)? This will definitely test the my DIY limits significantly, so just want to make sure I'm not overlooking something obvious before I take on the challenge.

Thanks to anyone willing to offer their opinions!

The white wire is the wiggle wire.
 

Last edited by Jeremy Picciuca; 10-27-20 at 05:46 PM. Reason: adding pic
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Old 10-27-20, 05:53 PM
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Welcome to the forums.

Make sure all the tabs on the valve are clean.
You can remove the wires one by one and spray each crimped terminal with a small amount of contact cleaner.

We usually recommend checking for 24vAC when the valve isn't opening and should be.
If that is ok.... then the wiring inside the valve to the terminals is probably at fault requiring a valve replacement.
 
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Old 10-27-20, 06:55 PM
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There is no gas valve module - you need check the board's error code when the failure occurs - confirm it's a flame not sensed error, then use a meter to see if power is being applied to the gas valve after the igniter warmup period.

If there's no power, it could be the control board, a bad connection between the board and valve, or the valve itself and it will take further troubleshooting.

How old is your furnace? I ask because all the 58 series high efficiency models have a heat exchanger that's prone to plugging up causing massive co production -> yours should be checked for this problem particularly if it's over 15 years old. It can take a combustion test to confirm, but the failure produces a hot burner box (sides closest to you, the front of the box is supposed to be hot) and bad exhaust smell. If it's really bad, you'll see rust on the exterior of the secondary with the blower removed water leaking into the blower compartment.
This is a major safety issue.
 
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Old 10-27-20, 10:02 PM
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Thanks PJMax.
I'll try cleaning up the terminals as you suggest. Do you reccomend spraying conact cleaner directly on the terminals? or using something like a Q-tip to get in there?

Everytime I try to check the voltage with a meter, the thing fires up. That's actually what led me to realize that I can get it to start just by wiggling the wire/ terminal shortly after the igniter glows.

Thanks again for the suggestion!
 
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Old 10-27-20, 10:05 PM
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^It may be worth replacing the terminal on the wire going to the valve - the connection can degrade, it's just a crimp on.

 
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Old 10-27-20, 10:17 PM
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THanks for the reply user 10!

"There is no gas valve module - you need check the board's error code when the failure occurs - confirm it's a flame not sensed error, then use a meter to see if power is being applied to the gas valve after the igniter warmup period.

If there's no power, it could be the control board, a bad connection between the board and valve, or the valve itself and it will take further troubleshooting."


Error codes are first ignition proving failure (#34) and then after 3 failed attempts to ignite, Ignition lock out (#14).

"How old is your furnace? I ask because all the 58 series high efficiency models have a heat exchanger that's prone to plugging up causing massive co production -> yours should be checked for this problem particularly if it's over 15 years old. It can take a combustion test to confirm, but the failure produces a hot burner box (sides closest to you, the front of the box is supposed to be hot) and bad exhaust smell. If it's really bad, you'll see rust on the exterior of the secondary with the blower removed water leaking into the blower compartment.
This is a major safety issue."


The furnace is about 20 years old. Maybe a few years older. I'm curious about this major safety issue.I have a few CO detectors in the house. I've never noticed a bad exhaust smell or a hot box, but i've also probably never tried to touch the box while it's been running since I would just assume it would be hot ! What's the best way to determine if my furnace is affected?
 
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Old 10-28-20, 03:14 PM
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A professional would do a combustion analysis - with normal gas pressure and all other causes ruled out, a plugged secondary will show as very high carbon monoxide and low oxygen.
I believe carrier says over 200 or something is a failure but you can search and see some being tested on youtube -> the monoxide is in the thousands!
Produces a hot burner box after running long enough - the sides near the heat exchanger inlets are supposed to be hot, but the rest should be warm to the touch at most.

You can pull the blower and look for corrosion on the secondary. When the coating fails, the metal gets exposed to the condensate and starts rusting from the inside out.

You can remove the drain trap, flush it out and make sure it has no rust/plastic flakes in it. Some black mold/algae stuff coming out is normal.

Hopefully yours is okay - just good to screen for the problem.

---------
As for error code - yes, gas valve probably not opening and it sounds like a connection is failing.
 
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