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    coldinmo's Avatar
    coldinmo Posts: 1, Reputation: 1
    New Member

    Oct 27, 2007, 12:35 PM
    Goodman Furnace - 3 Blinking lights
    I have a Goodman model GMNT 080 4B. The furnace start like normal but when the temperature reaches about 64 degrees I receive an error light. The fan continues to run but the burners do not. I have already tried cleaning the flame sensor but the problem continued.

    The error indicator light is flashing 3 blinks. According to the service panel this indicates 'Pressure Switch Failure to Close". Check Venter, Pressure Switch, Vent Blockage.

    What does the pressure switch look like? And what does it mean by 'Venter'? I have already check to make sure the vents were open. Thanks in advance.
    wmproop's Avatar
    wmproop Posts: 3,749, Reputation: 91
    Ultra Member

    Oct 27, 2007, 05:02 PM
    Pressue is a black thingy that has 2 wires and a vac hose going to it,, check from start to end and make sure vent isn`t stopped up,, birds nest, or anything in way of venting
    labman's Avatar
    labman Posts: 10,580, Reputation: 551
    Uber Member

    Oct 27, 2007, 05:15 PM
    You may find a picture of the pressure switch in the sticky at
    The vent it refers to is not the one your heat comes out of, but the one the combustion products from the furnace exits, a form of chimney.

    The problem sounds to me more like a high limit switch. Reading through the section of the sticky on sequence of operations will help you undestand everything.
    T-Top's Avatar
    T-Top Posts: 1,871, Reputation: 100
    Ultra Member

    Oct 27, 2007, 05:21 PM
    Check to make sure the vent pipe on the furnace is clear(hot gas exhaust). Check the small rubber tubes going to the pressure switch to make sure they have no holes. You can blow and suck lightly on the tube connected to the pressure switch to see if it is stuck(listen for a click when doing this).
    goodmanmey1's Avatar
    goodmanmey1 Posts: 3, Reputation: 1
    New Member

    Oct 2, 2009, 12:53 PM
    I had the 3 blink problem on my GMNT080-4b. After fighting it for a couple of years and (according to the installer) having the goodman rep look at it, the problem turned out quite simple. At least that is how I would describe the installer! The spec says this unit requires the 3" pvc while the installer installed 2". Why didn't the rep find this? This unit requires 3" regardless of line length! I changed to 3' and so far the problem is gone!
    wmproop's Avatar
    wmproop Posts: 3,749, Reputation: 91
    Ultra Member

    Oct 2, 2009, 06:47 PM
    The original thread was posted 2 years ago,, I hope the problem has been resolved by now
    lkovacs's Avatar
    lkovacs Posts: 1, Reputation: 3
    New Member

    Oct 31, 2009, 10:59 AM
    This is posted 2 years too late for the OP, but I have similar 3 blinking light lockout on my Goodman GMS8 model and here's what the problem was in case someone else has similar problem. Disconnect the rubber hose at Pressure switch end leading into inducer motor. Blow in rubber hose and see if the nipple from inducer motor is blocked up with crud. You should be able to blow freely into the nipple of the inducer motor. My was blocked so I cleaned out by inserting a small drill and rotating by hand to remove crud.
    jacquir's Avatar
    jacquir Posts: 1, Reputation: 1
    New Member

    Dec 14, 2009, 10:30 AM
    Hi - I seem to be having the same (or at least similar) issue with my Goodman Model #GMNT080-4B Serial #0405209221 heater/air conditioner unit. Here is specifically what is happening:

    The heater will fire up... the burners start up and air starts blowing, a few minutes later the system shuts down and then recycles itself and tries again. Eventually the "3 blinking lights" thing described above happens. I did have the limit switch changed, and that didn't help the problem.

    Last spring I had someone investigate the problem. They eventually came to the conclusion that the main vent pipe to the outside (this is in a condo, so it runs the whole length of the condo in between floors) was pitched wrong... and that it would be "thousands of dollars" to fix. Now, the condo is 5 years old, so it seems odd that suddenly the pitch would be wrong... it worked fine for 4 1/2 years. Thankfully I don't live there full time, so I had time to get a 2nd opinion.

    I had someone else come in, and he didn't believe it was the pitch of the pipe. He thinks it's either the inducer motor or the little box that all of the pipes lead into right before the motor (he said there's a "vacuum effect" in that box, and it's possible that's causing problems). He thought it was really possible to be the motor, because it sounds like there's almost a low-level gurgling kind of sound when it's running... but he's not positive.

    The 2" or 3" PVC pipe response above sounds interesting too... I will have to check that. The 2nd guy did pour some water into one of the hoses and did confirm that water runs through to the outside, so *if* it's a block, it's not a complete block.

    Any thoughts?
    Gingerlyhall's Avatar
    Gingerlyhall Posts: 1, Reputation: 1
    New Member

    Feb 2, 2010, 10:35 PM
    I am having very similar problems! I too have a Goodman Gas Furnace. The furnace will work for several hours (or minutes) and then kick off. I get the "pressure switch blocked" code. The rubber tube does have some water that is blocking it. Once this water is sucked out, the unit will begin to function. I have had 4 HVAC techs out to my home and each of them are stumped as to where the water/condensation is coming from. They have replaced the inducer motor, pressure switch, limit switch, thermostat, and control board. They even "unblocked" the drain (not sure WHICH drain) and assured me that it would work. Big surprise when it ceased again just a few hours later. I did read some feedback to other questions regarding the gas exhaust. Is there more to this? How can I ask the techs to check for this? Any other ideas WHERE the water could be coming from? I need help!! I'm a single mom with five little ones and we need heat!! :(
    sampogna's Avatar
    sampogna Posts: 1, Reputation: 1
    New Member

    Oct 4, 2010, 08:34 PM
    Comment on lkovacs's post
    THANK YOU! I had the same problem. I used a toothpick, and the system is working fine.
    amountain's Avatar
    amountain Posts: 1, Reputation: 1
    New Member

    Nov 20, 2010, 10:29 AM
    I took more than three weeks to fix the issue of "three blinking". I changed new pressure switch and new ignitor, but it still doesn't work.
    Finally, I decided to ask help from professional technician. Before I call the technician, I just don't want to take my failure with spending three week. Then, I googled the issue again and found this ticket. Immediately, I went down basement to test my rubber hose. I can not blow any air to the motor, but I did not have a long enough drill to clean the hole. I took out the hose from both ends of pressure switch and motor. It looks like that the hose is clean well. The only issue is from the nibble of motor, I used a drill to insert the nibble until I reached the inside of the motor. Finally, I connected both ends of hose.

    When I turned on the heating from thermostat, the ignitor began to become redder and hotter, then the gas come out, the fire flame came out.
    Rselwyn's Avatar
    Rselwyn Posts: 1, Reputation: 1
    New Member

    Nov 25, 2010, 11:06 AM
    Blow on pressure switch side of rubber line and it worked. Does anyone know why this line is problematic? Same problem every Nov/dec.
    goodmanmey1's Avatar
    goodmanmey1 Posts: 3, Reputation: 1
    New Member

    Nov 26, 2010, 01:38 PM
    I had the short run problem for two years. I read all about the 3 blink cures, the pressure switch, clear the air line etc. . I finally read the product specifications and found my problem. MOST FURNACES USE A 2.00 INCH pvc INLET AND EXHAUST AND ASSUME THAT IS CORRECT FOR ALL FUNACES. THE GOODMAN OVER 80,000 BTUH requires a 3.00 PVC inlet and exhaust. I installed the 3.00 PVC lines and my problem is fixed. It now works as is was always supposed to. It's a shame the home owner has to fix the so called expert's goof up. Anyway it now works.
    goodmanmey1's Avatar
    goodmanmey1 Posts: 3, Reputation: 1
    New Member

    Nov 26, 2010, 01:40 PM

    The 80,000 btuh requires a 3.00 PVC inlet and exhaust to work!!
    jcwhitejr's Avatar
    jcwhitejr Posts: 2, Reputation: 1
    New Member

    Jan 5, 2011, 08:46 AM
    Have a goodman gmp125-5. The blower comes on and off when the thermosat is off. Could this be the thermosat or something with the control board?
    jcwhitejr's Avatar
    jcwhitejr Posts: 2, Reputation: 1
    New Member

    Jan 5, 2011, 08:47 AM
    I have a goodman gpm125-5. the blower comes on and off when the thermosat is off. Could this be the thermosat or the control board?
    ITHelp33's Avatar
    ITHelp33 Posts: 1, Reputation: 1
    New Member

    Jan 27, 2011, 07:17 AM
    I just started to have the same issue you guys are describing. I will test some of your theories and post an update.
    cbwwc's Avatar
    cbwwc Posts: 1, Reputation: 1
    New Member

    Feb 5, 2011, 09:58 AM
    I woke up this morning the house was cold, 60 degrees. The furnace must have shut off over night. After some investigation I noticed the 3 blinking lights. Not knowing what the vent pressure switch looked like I looked at the wire schematics and followed the wires from the circuit board to what I assumed was the switch. I noticed the rubber hose, so I pulled it off, squished the length of the hose with my fingers to make sure there was no blockage then hooked it back up. The furnace fired right up

    Once the furnace was working I went online to see if I could find anything info on this topic and I found these posts. These posts confirmed that a blocked hose was the issue. I will now unhook the hose and clean it out properly.

    Thanks to everyone that has posted there comments on this issue they have been really helpful.
    tonyg556's Avatar
    tonyg556 Posts: 1, Reputation: 1
    New Member

    Feb 23, 2011, 08:53 AM
    I just had this 3 blinks error, and after reading the posts above, decided to check my black tube. The tube was clean as if it were new. I blew through it, reinstalled it, powered up the furnace and watched as it still had no flame. While it was still trying to run, I removed the cover, pulled the black hose off the pressure switch, tapped my finger on the end of the hose, to verify that it had vacuum and replaced it. After reinstalling the cover, I walked away to let it cycle out, figuring I would have to go check the blinker again. Next thing I know, there was warm air blowing from the vents. When I went back to the furnace, it had fire and was running like a champ.

    Maybe there was just a slight blockage and the sudden changes in vacuum, from my tapping the hose, helped to clear it out. Not sure, but it is working now. Thanks to all for posting in this forum. Hope my post helps, too.
    wmproop's Avatar
    wmproop Posts: 3,749, Reputation: 91
    Ultra Member

    Feb 23, 2011, 02:37 PM
    Round black plastic mounted to furnace with small rubber hose/tube running from vent motor assemble to the pressure switch

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