York G8C Furnace not lighting

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Old 10-09-18, 05:28 AM
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York G8C Furnace not lighting

Greetings all - having an issue with my gas furnace, as fall weather approaches here in Michigan I'd like to get it functioning again.

1. Grand Rapids, MI. Currently in the 60's, winters from 0-40 degrees F.
2. 1923 bungalow, forced air gas furnace.
3. York G8C Model 7516. Model # FG807516MU12A. Installed in 2002 (we recently bought the home, sometime in the span of the last 15 years it was turned from a single owner into a rental unit and was in rough shape, been working non-stop since)
4. Natural Gas
7. Digital thermostat.

Details:

Came home from camping last week, temps were in the 40's. Decided to turn on the heat to warm up a cold house (should have made sure furnace was clean and ready to go for the first time of the season, my fault). Furnace kicks in, starts blowing warm air, smell something odd (I'm thinking it was dust burning off, the furnace is located in the basement outside of my woodworking shop). Since then it won't complete the ignition sequence and light.

So far:

Cleaned flame sensor (I don't think this was it, as the flames never light. If it was the flame sensor I believe it would shut off after a few seconds of lit burners)

Cleaned gas valve and gas supply (inspected gas supply, checked screens/filters on gas valve, totally clean, no rust/dust on burners or orifices)

Furnace has power, gas works elsewhere in the house (stove, dryer, no problems).

When I attempt to turn the furnace on and provide heat, everything seems to run fine with the exception of no actual flame. Temp set to 70, vent blower runs, hear the click from the gas valve, ignitor glows red hot, no flame actually starts. Sequence repeats itself 3 times before locking itself out and giving my 7 flashes on the LED. Manual says that there is a problem with the gas valve, ignitor, or flame sensor (thanks, manual).

Since cold weather is forecasted later in the week, I have parts that I'm waiting on delivery. New gas valve, new ignitor, and I'm thinking of ordering a new limit switch just in case.

Other info: Furnace is clean, filters are new, no obstructions to air supply. If I turn the thermostat to Fan/On, the fans kick on and circulate air throughout the house. The central AC also works if turned on. Currently thinking it could be either the ignitor failing (it glows hot, not sure if it's reaching the proper temp to ignite gas or if the entire surface is heating properly. It's at least two years old, and probably closer to 10 based on the condition of everything else in the house when we bought it). Could possibly be the gas valve, but I'm not sure - I hear the click of the valve when it calls to ignite, but I don't smell any gas at all. Other thought was the Limit Switch (I've been doing some reading and apparently the limit switch can either burn out or lock out the system to prevent overheating? I don't see a button or switch connected that I can hit to reset it).

Any advice and help is greatly appreciated!
 
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Old 10-09-18, 12:31 PM
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Sounds like you have it narrowed down to the gas valve. Make sure the gas is turned on to the furnace. If the igniter glows then all your safeties are good.
 
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Old 10-09-18, 06:53 PM
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Welcome to the forums.

The 7 flash code is a one hour lockout code. You need to restart the furnace and then see what code you get. You should get a lower number. Since you are seeing the igniter glow..... you may have a gas valve issue. Be advised that gas valves are extremely reliable. I'd put more blame on the control board. What you need to do is to put a voltmeter on the gas valve to see if it's getting 24vAC when the burner should light. If it is.... the valve may be bad. You should hear it clink when it should fire. Don't be fooled by the click of a relay on the control board. The link below is the manual for your furnace.

York furnace manual
 
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Old 10-10-18, 04:57 AM
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Thanks guys.

@PJmax:

How do I restart this furnace? I've cut the power many times (while cleaning, checking parts, etc) but I haven't seen a switch or button anywhere that would "restart" it. There's a simple single pole switch wired outside, but that's only for power coming in. I've used both that and the breaker itself while working on it, and every time I test it to light the furnace I get the 7 flashes.

I'm currently at work, but I'll check the gas valve for 24V when I get home. And I've definitely heard a "click", but you're absolutely right about the possible differences between the relay and the actual valve "clink" noise.

Thanks for your help!
 
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Old 10-11-18, 04:46 AM
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Update for the thread:

Installed new igniter, ran through the process, no ignition. That's ok, at least I know my ignitor is new and should last for a few years.

Next step; hooked up the volt meter to the gas valve and watched the AC draw during the starting process. Watched it go from 13V AC to 26V AC three times (along with the corresponding click from the control board) before locking out again. Immediately went and ordered a replacement gas valve from Repair Clinic, as soon as it arrives I'll install it and update the thread.

Thanks for your help guys!
 
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Old 10-11-18, 07:49 PM
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Watched it go from 13V AC to 26V AC
That's interesting. It should go from 0v to 26vAC.

Anyway..... if you have the voltage at the gas valve and it's not opening.... it's bad.
 
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Old 10-12-18, 09:35 AM
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Originally Posted by PJmax View Post
That's interesting. It should go from 0v to 26vAC.

Anyway..... if you have the voltage at the gas valve and it's not opening.... it's bad.
Hooked up the gas valve last night, triple checked everything, and it started up instantly. Very nice to have heat on as the temps drop below 40F.

I'm reading and apparently the 13V could be an ungrounded wire? Everything looks simple enough as far as the wiring, I'll double check all connections again.
 
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Old 10-12-18, 04:31 PM
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Well done........ good job.
 
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