Furnace cuts out because of "low air flow", then starts again
I have a Goodman furnace model GMPN080-4, installed in 1996. We bought the house in 2003.
The problem: The furnace will run for a while. Then the gas will cut out and the red error light will flash 4 times, signalling not enough air flow. The fan will keep running. Within 30 to 60 seconds, the igniter will come on again and the furnace will start up again. It will do this over and over until the thermostat temperature is reached.
In March of 2008, we had the two heat exchangers replaced (under warranty), as well as the gas valve and flame sensor. This past January, we had the flat ignitor replaced, as well as the electrical on/of switch (which was actually burning...I suspect it was the real problem and the ignitor didn't need to be replaced).
We have had two service people in, who have assured us that the furnace is safe, but they haven't been able to give us any advice on how to fix the problem. One just said "Replace the furnace," and the other kept saying "There's not enough air flow," but couldn't give any suggestions on how to fix it.
We are using a cheap paper filter, which I now change once a month. When we moved in, the "permanent" air filter was in use, but I can't imagine it filtered out much of anything.
All of the return ducts and vents are clear.
Any suggestions are welcome! Thanks!
Thanks for your reply! The furnace runs fine without the filter or the front panel on (but of course I can't leave it like that). The disposable paper filter I am using now has the same Merv rating as the permanent filter that came with the furnace. I've put the old one back in to see what happens.
What I don't understand is what's causing this problem now after 13 years...Thanks for your reply! The furnace runs fine without the filter or the front panel on (but of course I can't leave it like that). The disposable paper filter I am using now has the same Merv rating as the permanent filter that came with the furnace. I've put the old one back in to see what happens.
What I don't understand is what's causing this problem now after 13 years...
Thanks for your reply! The disposable filter I'm using has the same merv rating as the permanent one, and it's cleaner. I tried putting the old one in but the same problem occurred. The furnace runs better without the filter and with the door off, so I can confirm that the problem is lack of air...not sure what else I can do about it though.Thanks for your reply! The disposable filter I'm using has the same merv rating as the permanent one, and it's cleaner. I tried putting the old one in but the same problem occurred. The furnace runs better without the filter and with the door off, so I can confirm that the problem is lack of air...not sure what else I can do about it though.
Thanks for your suggestion! We've since had the furnace replaced but....one thing we never tried that someone else suggested later was that the tubing that took away the condensation may have been blocked. You might want to try that for your problem.Thanks for your suggestion! We've since had the furnace replaced but....one thing we never tried that someone else suggested later was that the tubing that took away the condensation may have been blocked. You might want to try that for your problem.
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Re: Furnace cuts out because of "low air flow", then...
I have the same problem with my furnace. One technician told me I needed to have more cold air returns installed. It was too pricey for me to do, so I am just dealing with it for now. Maybe doing this will help you?
Re: Furnace cuts out because of "low air flow", then...
Try the furnace without the filter. if it stays running then find out what filter came with the furnace. if you have the owners manual. look for the simple things first. blockage, is the motor and fan runnin properly.. good luck
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According to this page, you can usually fix this 4 blink diagnosed problem by changing the air filter or tightening wiring (which it has a cautionary warning about tightening such too much) and checking the flue for blockage. The furnace has activated the primary open limit circuit.
Poor air flow in the Goodman caused by blockages can result in the tripping of the rollover switches which would cause it to blow cold air. That is a safety measure. You don't want gas furnaces burning with insufficient air. Think carbon monoxide. Besides the air filter, the flame sensor or the burner could be dirty. The idea of trying to DYI that cleaning job is rather off putting. I hope changing the filter would work.
I trust it is not a fuse in the pilot flame sensor circuit blown. A repairman has the voltage testers for checking the electronics involved.
I can empathize with this. My furnace, another brand, went out recently. The repair man didn't know why it went out but simply adjusted a handle controlling gas flow to a position slightly different from what was recommended and it worked. All for $200.
The model number you listed is for the outside unit which does not have a filter. The indoor part of this system (the furnace or air handler) is what has the air filter. The size varies because the installer usually makes a bracket to hold the filter when the furnace is installed. Need to locate the filter and replace it with the same one. Size should be marked on the old filter.
Sounds like the furnace is tripping off on a limit safety, either temperature or air switch. Check filters and restrictions to air flow (furniture over return air grills, blocked filters) also, check the drainage line of the system. If the furnace can't drain water fast enough it will back up internally, and trip the system off on a pressure switch safety.
It really depends on the type of system you have. You will either have a furnace, high efficiency furnace, heat pump system, heat pump with gas or electric back up heat. All these systems operate differently and the problem that you are having could be caused by multiple issues, depending on which system it is. More info will be greatly appreciated. Make sure to check all filters and air flow first before going any further. The system could be over heating and tripping a limit, causing the system to stop producing heat until the unit has cooled back down.
You might try checking your return filter. The new filters (pleated 3 month, ie real expensive ones) cut back your air flow 35% from the amount the regular 30 throw away allow. When air flow reduces the temperatur from furnace increases and can cause inadvertant high temperature limits to trip. If you are using a clean return filter, next you need to physically observe the air inlet side of your cooling coil to see if it is blocking air flow due to being dirty. If you have trouble with seeing the inlet, you might need to get a professional to take the air handler apart.
I suppose this furnace is fueled by Natural Gas? (Or is it Propane-- Bottled gas?)
Did the Service company leave you any manual, with your new furnace? and I would think there was a warranty, for assuring you (the customer) satisfaction, no? Have you called the people who sold/installed it? What do they say?
If they did leave a manual-- what does it suggest for narrowing down your possible problems? Like: Low Fuel-- Low Voltage- Filter Changes, Fan switch problems- or ignition failure problems?
For a new furnace, someone should be right there to do a start-up for you!
The blower motor is only going to pull a certain amount of CFM for circulation air. There is some restriction of air flow that is created when the return air system is ducted causing the air flow to "slow down" a bit. The air going into the furnace firebox is probably moving at a faster rate than if the return air was ducted. It will work and you will get the same amount of heat (energy) released but the faster moving air will make it feel cooler. Also the unit might be undersized(BTU output) for the size of the cabin and amount of airflow the blower is creating. Adding a extra filter(double) might slow down the air flow a bit to create more warmth(feel) coming from the registers. Also if the furnace and air intake is pulling air from outside(garage,closet, or under house) then the colder air from outside going into the system will decrease the heat from the furnace. It is better to have a closed system (return air inside cabin). You might want to try adding a extra filter to slow the air flow down some or use some sheetmetal and square it from the intake to try and concentrate the incoming air a little better and see if that improves the warmth coming from the furnace.
Try replacing the filter. Low air flow will allow the furnace to overheat. Sounds like a simple answer. Wish I had tried it before buying a flame sensor and controller. Live and learn I guess.
Thanks for your reply! The furnace runs fine without the filter or the front panel on (but of course I can't leave it like that). The disposable paper filter I am using now has the same Merv rating as the permanent filter that came with the furnace. I've put the old one back in to see what happens.
What I don't understand is what's causing this problem now after 13 years...
Thanks for your reply! The disposable filter I'm using has the same merv rating as the permanent one, and it's cleaner. I tried putting the old one in but the same problem occurred. The furnace runs better without the filter and with the door off, so I can confirm that the problem is lack of air...not sure what else I can do about it though.
Thanks for your suggestion! We've since had the furnace replaced but....one thing we never tried that someone else suggested later was that the tubing that took away the condensation may have been blocked. You might want to try that for your problem.
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