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.

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

You may find a picture of the pressure switch in the sticky at https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-frequently-asked-questions-58313.html
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.

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).

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!

The original thread was posted 2 years ago,, I hope the problem has been resolved by now

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.

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?

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!! :(

THANK YOU! I had the same problem. I used a toothpick, and the system is working fine.

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.

Blow on pressure switch side of rubber line and it worked. Does anyone know why this line is problematic? Same problem every Nov/dec.

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.

The 80,000 btuh requires a 3.00 PVC inlet and exhaust to work!!

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?

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?

I just started to have the same issue you guys are describing. I will test some of your theories and post an update.

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.

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.

Round black plastic mounted to furnace with small rubber hose/tube running from vent motor assemble to the pressure switch

I had the error light (3 blinks) on my Goodman gmt090-3b furnace. The vent van would start up but the gas would not turn on and the furnace would not fire up. I was able to fix it by cleaning out the little nipple that the vacuum hose runs into on the vent fan from the pressure switch (2" round thing with 2 yellow wires and the vacuum hose running out of it). I figured out it was clogged by taking the vacuum hose off the pressure switch and blowing into it (with the other end still attached to the vent fan). I couldn't get any air through it. So I removed the other end of the hose (now the hose is completely off) and stuck a little screwdriver down the hole and cleaned out the little hole. I put the hose back on (at the vent fan end) and was able to blow through it. I hooked the other end back to the pressure switch and it fired right up. It now works great. Thanks for the info above-- it really helped and saved me a lot of $.

I had the same problem 3 blinks the unit would come up and run ,burners fire up but then shut down. After reading this thread decided to get on the Roof and check for a birds nest possibly blocking the ventor pipe.
I live in Northwest Florida, there was no birds nest but could see something behind the plastic screen,after pulling the screen cap off 2 huge wasp nest fell out. Problem solved.

Thanks to everyone. I just disconnected the rubber hose from both ends and blew through it in both directions. There was definitely an obstruction. I used a wire clothes hanger to clear some guck and now everything works fine.

I've tried all of the above. Cut 3" vent to even check for a clog, nothing. Checked hose going into pressure switch blew both ways and was clear. Furnace will run for 15 minutes then give me 3 blinking lights. Take hose off blow again works for 15 minutes goes out. Bad pressure switch? I don't know what to try next.

I'm actually getting a lot of moisture when I pull the exhaust vent out of the fan. Could it not be draining properly?

Just had similar trouble. Tried blowing in the tube but that didn't do the trick. Then I used a compressed air canister to blow it out and now is working. So perhaps try something a bit more forceful than your breath? Not sure but worked for me.
Thanks everyone for your input!

Thanks for the info on how to fix the 3 blinking light issue it was very helpful. I had that same problem. I found the motor and the tube going from the fan motor to a device which I assume was the pressure sensor. I was able to stick a 3/32 drill into the hole in the motor for about 1 inch. I tried a 1/16" drill and after turning it around, it broke loose some stuff and went in further. But the drill was not long enough to go further and it seemed that there was still more stuff inside. So I got a piece of 18 gauge steel wire (I didn't have larger wire) and pushed it through and scraped it on the sides of the hole. It seemed to clear out more stuff. Once it was reassembled, the furnace burner came on. So this solved the problem with no parts and no expense for a furnace repair person.