Furnace starts hour after call for heat


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Old 11-22-08, 11:00 AM
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Furnace starts hour after call for heat

I have an Aire Flo forced air gas furnace. The furnace was installed in 2004. It was fine last season, but has been intermittent so far this one. The LUXPRO stat makes a call for heat and I hear the gas then the flame but the fan doesn’t come on and the furnace shuts down.

We had a repair technician out, but the furnace worked perfectly while he was here. One morning when the furnace was acting up I did notice the LED on the board was giving 2 flashes which according to the manual indicates “Ignition re-try or recycle error”. When the furnace isn’t working switching the fan to “on” doesn’t do anything. It is working right now, but only after the stat called for heat about an hour earlier.

The technician that came out removed the flame sensor and cleaned it up with sand paper, but it didn’t fix the problem.

Any ideas?
 
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Old 11-22-08, 01:11 PM
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It could be caused by anything with ignition process, or venting, msot likely. Things repeatedly posted here on this forum. You will have to either do many of the suggested routine maintenance, or catch it in act, as you watch for it to occur. And obviously if it only does that once in a great while, that is problematic.

Make sure condensate water can drain, that all electricals are good.

What type of ignition do you have? HSI glow coils sometimes can go weak, yet still work sometimes and not other tiimes. And with spark/pilot systems these are problematic in losing sensing to ground or a somewhat clogged pilot oricfice. Or if you have direct spark to burner, associated failure with spark. So it be nice if you say what type you have.

If there is an issue with the pressure switch, usually you will not even get the ignition process to continue. But if you do not even know if it does, because it is infrequent, you could maybe learn SOMETHING if you have the type of pressure switch where you can see the plunger lift off the actual switch, to see if the plunger moves in and out, while drafting, and almost touches the switch while it runs. If it does this kind of behavior you likely have something interfering with the draft. It could be something as simple as where the vacuum tube plugs into the inducer, that it is filling up with crud in that hole, and you then just ream it out.
 
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Old 11-24-08, 08:06 PM
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We have HSI. I hear the gas and then the woof of the flame but shortly after that it turns off.

Here is a link to a sequence of operation.

Mobile Home Repair - Mobile Home Gas Furnace Operation Flow Chart

It is very similar to the one in my manual but not exactly. The main difference is that when the flame goes out it goes into lockout for about an hour then sometimes the furnace will work after that.

The technician that was here used sandpaper on the flame sensor, but I’m wondering if I should just buy a new one. It would be less expensive than having a technician coming out and not fixing it again.

On my sequence chart is says that the LED flashes 2 when it goes into lockout. That is exactly what it was doing shortly after a call for heat one morning. It works intermitenly. This morning the heat came right on when we called for heat, but now it is 7pm and the stat shows that it is 2 degrees colder than what the stat is set for.
 
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Old 11-24-08, 09:49 PM
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The furnace wasn't working again so I decided to remove the flame sensor and sand it a little. I put the sensor back in and turned everything back on. I saw the yellow flame then heard the hissing of the gas and a click but no blue flame. It cycled again...yellow flame...hissing (gas)...click...this time the gas lit and a few seconds later the fan came on. I thought that the gas was lighting before, but I didn't see if it was or not because the covers were on. Now I think that the gas hasn't been lighting and that's way it shuts itself off after 3 tries and goes to lockout for an hour. Could it still be the sensor? What would cause the gas not to ignite with a flame present?
 
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Old 11-25-08, 08:37 AM
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Your yellow flame in the beginning sounds like a pilot light that is not going good. If that is not going good, the flame sense ability there will not give the go ahead to keep any fire going.

You are going to have to remove the pilot assembly by disconnecting it from the main gas valve and pulling it out of the conmbustion chamber, and clean out the orifice down at the flame end.

If you do not have a pilot assemnbly, like I think you do, let me know. If you need further instruction, let us know.
 
 

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