Goodman GMP075-3 Acting Up

BlenderWizard

Alright, I am dealing with a Goodman gmp075-3. About ~2 months ago the flame sensor went out. After I changed it, the vent circulator would come on, and the flames would ignite, and the blower would come on as normal. However, before the furnace brought the house up to temp, the burner would shut down, the blower would go off and the vent circulator would stay on, then after about ~30 seconds, everything would start back up blowing warm air. This would happen several times until the house was brought up to temperature, depending on how far it had to go.

Now, not only is it doing this, but the blower kicks on when the vent circulator starts up, blowing cold air into the house before the burner fires up. i have changed the flame sensor twice this year (the second time was to make sure the first replacement wasn't a dud, because the furnace had ZERO problems until the flame sensor went out). I also recently changed the t-stat from a DICO to a digital AprilAir. Any help or ideas would be much appreciated. This furnace is about 6 years old.

ABTECH

I've seen similar issues like this where the furnace is actuaally tripping on high limit.Like the fan speed is too low or bi-metal in high limit is weak, poor air flow, etc..I've seen this bring on power vent and blower with no flame.? Just an idea,

Bestheating

That model has a few board problems, but since all functions are working, I would not think that to be it. If you have an intermittant pressure switch dropout, maybe from a plugged vent, you might have your symptoms. Are you getting a code fault signal on the board? Also, are you losing 24v at the gas valve? Don't forget to follow up on the post from ABTECH and do a temperature rise while it is running and see how it compares to the rating plate. You might not have enough air flowing through the system.

BlenderWizard

Well, not too long after my post on this, the weather warmed up, and I forgot about it. Now, the weather's getting colder, and I remembered


Anyway, the problem is still there, and the board flashes 3 times, which is a pressure switch error.

I guess I need to change the pressure switch? Any help is appreciated.

hf05

Sounds like it tripping on the limit for sure..Clean filters maybe!.These units i'm sure had x-changer problems like rings popping.The popped rings would usually trip a secondary limit on the burner box ,but if ones gone down by the primary limit it will overheat

BlenderWizard

Hey, thanks for all the help. I changed out my pressure switch, and about 90% of the problem is gone. It still turns the blower on with the exaust motor. I've asked all of my HVAC guys about this, and they all came back scratching their heads.

#CARRIERMAN

Hi BlenderWizard

You still have a problem with your blower board. This particular board picks up its delay time off of the flame sensor signal. Change out the board and you should be as good as a Goodman can get.

Good luck
Rusty

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Character is doing the right thing even when no one is looking. Intelligence is understanding and practicing the meaning of character.

BlenderWizard

Do you have any suggestions as to where to get one for a good price? There's a shop I buy from locally, but only if i need parts yesterday. They charge about double what many online retailers charge. I only us them in a pinch.

#CARRIERMAN

Hi BlenderWizard

If you have a Johnstone Supply or a Grainger you should get pretty reliable service at a descent price. However I have noticed that they vary prices from town to town on some items.

Good luck
Rusty

__________________
Character is doing the right thing even when no one is looking. Intelligence is understanding and practicing the meaning of character.

BlenderWizard

Grainger would have it? Cool, there's actually a few near me.

libertyforall

Note that Goodman Janitrol Changed this Flame Sensor's design December, 2006.

The new design is the vertical flame sensor picture.

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