Goodman 100-4 gas furnace ignition


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Old 01-28-19, 03:17 PM
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Goodman 100-4 gas furnace ignition

Hi guys,

Question on ignition for a gas furnace. Quick background. This natural gas furnace has been working fine for years, with occasional hiccup. Last year wouldn't stay lit after ignition, cleaned flame sensor with steel wool, and worked great. Last week I noticed that it wasn't igniting, so I took cover off and watched. Inducer fan starts off, but thermocouple or hotplate was not glowing, so I checked it with my meter and it had a hairline crack in it, plus it read open. I bought a new one, and installed it. Heater works now but I notice something different.
Inducer fan kicks on, then hot plate glows red, and I hear a click, I assume solenoid on gas valve and pffffft noise, I assume gas but furnace doesn't light on first attempt, like it always has. Then hotplate goes off, inducer fan continues to run, then glowplate kicks back in to glowing red and then this time it lights off. I thought maybe the gas valve was starting to crap out so I researched it goodman b12826-14, not much I can do with it and it's pretty cheap so I bought a direct replacement, white rodgers 36G22-254. Installed it today and it makes no difference it starts on second fireup of glowplate. I checked to make sure the gas valve was getting correct voltage it shows 15.5vac in a relaxed state, but when the command is given, glow plate on, it kicks up to 25.5vac.
I'm just curious why it's now taking two cycles to kick on. I will say this, once in a while it will fire off on first cycle. It never times out meaning 3 or more cycles, so I don't get any error codes. One other thing, maybe it's normal, when it first kicks on, meaning the inducer fan kicks on, I usually hear a click click click like a relay, maybe that's the inducer start relay or something. It's not coming from the inducer impellars, they free spin too, so like I said, that maybe totally unrelated and not a concern.
Appreciate any thoughts on it.
 
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Old 01-28-19, 09:01 PM
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Just a follow up. I have seen on the internet where most of the guys with their meters are testings these showing 40-90 ohms and theirs are usually 80 or below. Mine is 126 ohms cold. I stuck my meter on the wires going into the hot surface igniter, and when the demand is called it goes right to 120 vac and stays there, until it sees no light off and then goes dim again. I do notice on the second cycle that when the igniter comes on, it's on for a few seconds before it comes up cherry red and then the solenoid click for gas hits and it fires off. The first cycle, the igniter comes on, but it's orangish, but not bright red yet when gas solenoid clicks for gas. I'm wondering if either the board has a separate type of cycle that it kicks on for the igniter or timing, or if the igniter is (even though new) defective or going defective because that seems higher resistance than what I'm seeing on the internet with other people. And no I did not touch the igniter while installing it.
 
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Old 01-29-19, 09:43 AM
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All replacement igniters are not the same.
With a new supply coming in from Asia.... the specs and quality on many leave a lot to be desired.
 
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Old 02-01-19, 06:34 AM
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Well, I replaced the hotplate sensor and still mostly lights on second light up of hotplate, instead of first. New out of box sensor rings out 124ohms, so you got me what the deal is.
 
 

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