Pressure switch stuck open in Goodmans furnace with 3 blink code


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Old 11-02-13, 04:26 PM
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Pressure switch stuck open in Goodmans furnace with 3 blink code

Hello,

I have run into what seems like a common problem with my Goodmans furnace (GMS90904CXA) with 3-blinks code indicating pressure switch stuck open. Similar posts in this forum suggest inducer motor nipple clog as a common cause. So I am trying to clean it up with a paperclip.

My question is how deep can I go with cleaning inside the nipple? Should it be completely open?

I didn't see any deposits near the mouth and am able to go in about an inch with no obstruction before I see complete blockage with some white stuff. As far as I can tell peeping inside the hole, it appears flat, solid and uniform, and not crusty. So I am not sure if I should push the paperclip harder through it or leave it alone and call it clean.

Thanks in advance.
 
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Old 11-02-13, 04:42 PM
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A paperclip is probably too thick to clean out the nipple properly. It will likely go in the outside entrance of the nipple but fail to go into the smaller hole that goes into the compartment where the inducer fan operates.

I usually use a small drill bit to clean out the fitting properly. The drill bit should go into the compartment where the inducer fan is located. Usually you can feel the drill bit break through the corrosion that is preventing the air in the inducer motor housing area from getting to the pressure switch tubing.

If need be, you can remove the inducer motor assembly from the furnace by removing the bolts that hold it in place. That's usually pretty easy to do. Once the inducer motor fan assembly is removed, you can clearly see the drill bit poking into the inducer motor housing.
 
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Old 11-02-13, 09:41 PM
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Thanks for the quick reply.

The drill bit may have to wait a day or two before I can get one from the store. But I am attaching a couple pics. One shows the white stuff at the end of the hole, other shows the paperclip with respect to the nipple entrance. It can go all the way in.

Btw, I tried sucking from the tube from the inducer motor end and I can hear the pressure switch click. Also, tried placing a finger at the nipple entrance with the motor running and didn't feel any suction.

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Old 11-02-13, 11:08 PM
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The amount of suction is very miniscule. You'd probably not feel it by putting your finger over the hole. That port in the inducer does look to be blocked shut.
 
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Old 11-09-13, 04:01 PM
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I am back So... I am beginning to lean away from the nipple-clog as the issue here for a couple reasons. The white stuff I mention above rotates when the motor runs. Seems like it may be some sort of disc that may be tied to the motor shaft. It's more than an inch inside from the mouth and deeper than the length of the nipple. In my attempts to clear it, I was able to make some dents/holes in it, but they would be gone once the motor runs (hence, the disc theory). I haven't pulled the motor out yet to look from behind.

So now, I am thinking of changing the switch. I have already checked the tube. Like I said in previous post, the switch still responds to manual suction. Is it possible that it may have aged to the point where the amount of suction from the inducer motor is no longer enough?
 
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Old 11-09-13, 04:49 PM
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If the vent pipe exits the house at a place where you can get to it, create a call for heat & feel the exhaust. If it isn't blowing, you could have a plugged pipe. Sometimes wasps will get in there & build a nest.

Another way to test is to shut off the gas to prevent ignition & disconnect the exhaust pipe from the furnace. If the furnace then goes thru a complete ignition sequence (less flame), the vent pipe is probably plugged.
 
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Old 11-13-13, 05:41 PM
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I wish wasp nest was the case because we had them below the deck over the summer. But doesn't look like that's what it is. The exhaust is blowing and when I finally managed to get up there, I can see the pipe is fairly open with no blockage for at least about 2 feet. There is a second pipe right next to it with a downward spout which leads back to the burner unit and there is nothing blowing from it, should there?

Other ideas? Time to swap the pressure switch?
 
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Old 11-13-13, 05:54 PM
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That second pipe, with the downward turn, is probably the air intake. If you can, disconnect it from the furnace & try the ignition sequence again. If the pressure switch now closes, you have a restriction in the intake pipe. I hate to have you try one thing, then try something else but pressure switches rarely fail & to diagnose a problem by changing parts can get expensive pretty quickly.
 
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Old 11-13-13, 09:47 PM
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The intake pipe just opens in the burner unit, doesn't connect to anything. Would taking the front panel off of the unit have the same effect as disconnecting the intake (free airflow)?
 
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Old 11-13-13, 11:34 PM
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Yup.

----------------
Might want to make sure the drain line is clear.
 
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Old 11-14-13, 04:39 PM
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I did have to take the front panel off in order to access the switch and the problem is still there. So no dice there.

I do see the water moving from the drain line. So I assume it's clear...
 
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Old 11-14-13, 06:07 PM
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At this point the venter needs to be checked to see if it is pulling enough to close the pressure switch. If it is not, either the venter is bad or the heat exchanger in the furnace is plugged.
 
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Old 11-15-13, 09:22 AM
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I am having the same issue with a Janitrol furnace.

I have 2 Janitrol gas furnaces, installed in new contruction about 11 years ago. Since year 1 one of the units occasionally won't light. The company who installed the sytem changed several parts but over time the issue still existed. Once the warranty was up I didn't call them back because it was obvious they could not find what the real issue was.

I troubleshot the system, testing the different components that control the lighting and found the vent fan is the issue where the hose connects. If I run a paper clip into the hole it seems to clear it out and once I reconnect the hose it lights without a problem. I know the paper clip is going in far enough because I can fell it stop the an if I try to rotate it when the clip is in. I have used a small drill bit by hand but there is limited access. It seems to make it work longer. I suspected corrosion building up across the hole. I have sprayed a small amount of oil to hopefull stop the corrosion from bulding up but yet it still comes back every year.

The problem is I have to do this sometimes once a week. If I am not home or away on a trip my wife cannot do this and thus is without heat. I removed the fan unit in the thought of cleaning up the bottom side and applying a sealer but there is very limited access to the lower end of the tube.

I priced the fan unit and it is over $200. It appears this is a common problem, has the company issued any recalls or fixes for the issue? I am not convinced replacing the fan unit fill definitely fix the problem? Whats to stop the new one from doing the same thing!
It has happened only once/twice on one of the sytems but it is consistent on the other.
Any additional adcive would be greatly appreciated.
Thanks
 
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Old 11-15-13, 11:27 AM
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Grady - what is venter and how do I access it? Is heat exchanger the part that the flames blow into (less accessible than rest of the parts)?

bigmacva - by vent fan, do you mean the inducer motor or something else?
 
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Old 11-15-13, 03:15 PM
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What I refer to as the venter is the device you pictured.
That furnace has two heat exchangers. The first (primary) is where the flames are. The second (secondary), which you can see without some disassembly, probablty looks somewhat like a car radiator.
 
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Old 11-16-13, 09:44 AM
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Is there a meter I can buy that can measure the suction from the venter? Just seems odd that the motor is running and is also blowing through the outside exhaust, yet not having enough suction to close the switch.
 
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Old 11-16-13, 04:25 PM
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There is a meter you can buy but you can also make a gauge pretty simply. Here's how: RV U Tube Manometer
I would suggest attaching the tube equally high on both sides.

The one thing you would need to know is how much vacuum is needed to close the switch. It may, but not likely, be marked on the switch.
 
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Old 11-24-13, 02:50 PM
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I finally decided (and managed) to remove the motor and here is what I see for the rubber gasket. In everything I have seen so far, this is the first thing I see that's clearly broken/cracked. Could this cause the pressure switch issue?

Also, any ideas where I can buy furnace parts? Distributors I called don't sell to individuals, only licensed contractors.

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When I removed the coupling that connects the fan to the exhaust and ran the motor (with gas turned off), I can easily feel the draft.

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And here's looking inside the motor:

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Old 11-24-13, 04:15 PM
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I doubt those cracks are causing the problem but they could be. Regarding parts, I'd do an online search for "goodman furnace parts".
 
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Old 04-03-14, 09:31 AM
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Furnace switch stuck open

Hi, I used your post to fix my furnace. But I wanted to reply to your original question, How far do you have to poke the paper clip into the hole to get it clean? I used the paper clip and had no results but later used a 1/8" drill bit and had success! I don't think there is any distance to reach for, just as long as you scrape the inside diameter of the hole down to about a half inch. The greater the diameter, the more vacuum it can pull. So it may be the carbon build up on the inside wall cause the the problem. There wasn't much, just a tiny amount of dust like matter.
 
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Old 04-03-14, 10:25 AM
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Welcome to the forums.

What ever you use to open the port up needs to be slightly longer than the port so that it goes thru the port and blower cover. Usually an inch or so will do it.
 
 

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