Goodman furnace blowing cold air


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Old 10-29-13, 05:10 PM
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Goodman furnace blowing cold air

I have an 8 yr old Goodman GMs9 warm air furnace that for the past 4 weeks has been blowing cold air intermittently. It is reading a 6 led error code that. I can reset and will work again, the current technician working on it cannot figure out why this is happening and I Am getting frustrated with the lack of a fix. This is what has been tried venting the furnace outside to draw in cold air, trying a new. Induced draft blower and installing a new flame rollout switch, the furnace will not work unless the front cover is offend to me that is dangerous. I am wondering if this could be an electrical problem that is being over looked. Any help or insight is appreciated.
thanks adam
 
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Old 10-29-13, 05:47 PM
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One of the reasons for a code 6 is loose or improperly connected wiring. Since you say the furnace runs with the door off and does not when the door is on, start by checking for a loose or broken wire - probably being pushed by the door when it is in place.
 
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Old 10-29-13, 06:18 PM
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Normally when a furnace won't operate unless the front cover is off it is because there is a lack of air flow. Make sure your flue is open and not blocked or restricted by dead animals. bird's nests, etc. This will prevent the exhaust from escaping and cause your issue. Also make sure all of the supply vents are open and the return air grilles are all clear and unobstructed. Make sure there are no air dampers closed in the ducting.
 
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Old 10-29-13, 06:22 PM
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Now it is showing the error message with the door off as well, need to manually reset it
 
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Old 10-29-13, 06:25 PM
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Does the rollout limit switch trip?
 
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Old 10-29-13, 06:34 PM
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Yes it does has been replaced 2 times
 
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Old 10-29-13, 06:40 PM
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It is tripping because the furnace is getting too hot. It sounds like your exhaust pipe is blocked.
 
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Old 10-29-13, 06:47 PM
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Wouldn't the furnace guy check that as a problem, how can I trouble shoot this myself?
 
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Old 10-29-13, 06:50 PM
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Do you mean intake of cold air, because that is a new pipe we installed, or the existing exhaust pipe
 
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Old 10-29-13, 07:05 PM
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Wouldn't the furnace guy check that as a problem, how can I trouble shoot this myself?
You would hope the furnace guy would check it. I am talking about the pipe that carries the hot exhaust from the furnace out of the house. It needs to be checked to ensure the entire length of pipe is open from the furnace to where it exits the house. Have you ever observed the start-up sequence of the furnace to see if the flames are actually rolling out of the burner box and tripping the roll-out switch limit? I have seen roll-out switch issues caused by heat exchanger problems, gas pressure issues, mis-aligned burners, drafting problems and etc. Did your furnace guy check the heat exchanger?
 
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Old 10-30-13, 12:26 PM
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I have seen the start up process, looks good, the gas pressures have been checked and the burners are not misaligned from what I am told. The problem seems to be when it has run through a cycle and cooling down, that when the thermostat no longer calls for heat the furnace will stay on and blow cold air. I have another guy checking it out on Friday.
 
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Old 10-30-13, 02:59 PM
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Perhaps the blower continues to run because the high limit switch trips because of excess heat. I suggest you observe an entire cycle from the time a call for heat is made until the furnace shuts down. You need to determine if the furnace shuts off because it reached the target temperature or because the limit switch opened and shut it down and left the blower on to cool it off. If you observe this entire cycle you may see multiple error codes.
 
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Old 10-30-13, 03:43 PM
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Yes. I have done that, it is never consistent and it is now tending to occur during the cycle and always 6 red flashes. Recently had been shutting off with the cover on, once we took it off it was working well. Now shutting down midway through cycle and the limit switch is tripped.
 
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Old 10-30-13, 04:33 PM
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Intermittent problems are the most difficult to diagnose. You may already have this but if not here is a link to some info that might be of benefit to you:

http://www.acdirect.com/xcart/images...ts/IO-244F.pdf

The troubleshooting guide begins on page 34.
 
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Old 10-30-13, 04:38 PM
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Thank you have seen this, wondering if it could be electrical. In your opinion should these problems be occurring in an eight yr old furnace? so far have needed 3 induced draft blower motors replaced and the rollout switches were both replaced last year? Wondering if goodman is not very reliable
 
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Old 10-30-13, 05:15 PM
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It is difficult to say if it is electrical. HVAC equipment is only as good as the job the installer does. Proper installation is the most important aspect. A roll-out switch that keeps tripping is an indicator of a serious problem. That is the reason that roll-out switches are manual reset and not auto reset; so you will have to investigate the cause of the tripping. When your furnace guy comes make sure he does a thorough inspection of the heat exchanger. They can crack and fail rapidly when exposed to repeated over-temperature conditions. Then the flames can go through these cracks and trip the roll-out switches. Your heat exchanger should still be under warranty if there is an issue with it.
 
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Old 10-30-13, 05:21 PM
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Another question there has always been a steady red led indicator on, I was told this was normal, did I get bad information.
 
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Old 10-30-13, 05:30 PM
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According to the troubleshooting page I linked steady on is normal operation.
 
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Old 11-01-13, 02:57 PM
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The new tech is here asked if noticed black soot which I had, says that should never see soot with propane! is this true? I had asked my previous guy and stated it was normal.
 
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Old 11-01-13, 04:43 PM
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Any soot is bad soot. A properly running system should never produce it. Can happen with lack of proper combustion air or over a long term even a dirty pilot will create soot. Depending how long it's been going on it may well be in your exhaust vent. Soot anywhere allows more soot to expound itself.
 
 

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