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Troubleshooting A Goodman Furnace

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Old 11-09-2010, 05:30 PM   #1
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Troubleshooting A Goodman Furnace

New guy around here, looking for a little help.

I'm a pro reefer tech/food equipment tech struggling to get my mother's furnace going. It's a fairly new Goodman GKS9090.

It locks out on a single flash error code, no ignition. The blower comes on, the igniter lights up but I get no ignition. I have verified that there is gas to the unit and I see 27v at the gas valve but no flame.

I don't know much about domestic HVAC so I'm wondering if the sequence is correct. the blower comes on for about 15~20 secs, then the igniter lights up but the the gas valve only gets juice about 5 seconds later, and only for about 2 or 3 secs, then it shuts down. I don't know if this is correct, it doesn't seem like that is long enough to fire up and prove a flame to the sensor. There is no port upstream of the valve to hook up my manometer so I'm not sure if the valve is actually opening for the breif time it gets juice.

Trying to figure out if I have a bad board, a bad GV, or something else. Would like to find a link to Goodman technical info.
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Old 11-09-2010, 06:45 PM   #2
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Re: Troubleshooting A Goodman Furnace

The board usually won't even allow the igniter to fire up until draft induction is proven (pneumatic or centrifugal switch). It sounds like you are past that point. The blower you're talking about is probably the combustion blower, and 15-20 seconds is not unusual.
You said igniter lights up and voltage is applied to gas, but no flame... but you haven't said if gas is flowing.

If you're not getting flame at all and there is voltage at the gas valve, do you smell gas at the furnace? If there is gas at appliance(input side), and gas isn't flowing, its the gas valve, or clogged orifices.

Sounds like you're dealing with a hot surface direct ignition. An electrode in a flame acts like a diode and when an A/C voltage is applied, it is rectified. The control unit senses the rectified current to prove flame and gives a limited time frame before flame is proven or it shuts down, but if its not lighting up at all, this probably isn't it.

If you've got plugged orifice preventing the sensor from touching the flame, or the rod is dirty, it won't see the current. You should see a sensing electrode somewhere in the flame. Clean it with a wire brush. If the ceramic insulation is damaged, it needs to be replaced.

You will always smell gas from failed ignition attempt.


Last edited by Electric_Light; 11-09-2010 at 06:57 PM.
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Old 11-09-2010, 07:25 PM   #3
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Re: Troubleshooting A Goodman Furnace

Isn't that a Gemini gas valve?

look for a small hex screw on a raised port. You only turn the hex loose, you don't remove it. You put your hose over the port with the hex screw loose.
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