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Matthew, HVAC Technician
Category: HVAC
Satisfied Customers: 2014
Experience:  14 years experience in the HVAC field of service, installation, Manual J & D calculations
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Furnace keeps running but no heat through the vents

Customer Question

My furnace is running almost non stop, there is heat but it is not blowing up through any of the vents

Submitted: 7 years ago.
Category: HVAC
Expert:  Matthew replied 7 years ago.
If the burners are on and the blower is running but you do not feel air coming out of the registers then you either have a very dirty filter or your evaporator coil which is the A/C portion inside that sits on top of the furnace is plugged up and no air is going through. If this is the case then this furnace should be kicking off on high limit eventually.
Customer: replied 7 years ago.
the filter is brand new, there is a red light that blinks on the circuit board though, if i turn it off and then back on then it will sometimes blow air for a minute or two and then stop again
Expert:  Matthew replied 7 years ago.
This light blinks a code see what the blink code is giving you. And I am not recognizing that gmt brand is that the model number maybe and not the manufacture name?
Customer: replied 7 years ago.
it blinks 3 times and then pauses and then does it again, i live in an apartment and the owners manual was the only thing i could find with any sort of name in it, i tried finding a serial number or something but found the warranty and an installation manual, the warranty says models gmp, gmpv, gmpe, gmph, and gpd and its made by goodman manufacturing company
Expert:  Matthew replied 7 years ago.
This 3 blinks means the pressure switch failed to close. This is the round cylinder with 2 wires and a rubber hose coming off of it. Take that rubber hose off and blow through both ends then take a paper clip and clean that little hole on the inducer motor where the hose hooked up. Put it all back together and try again. If it still does not work then take the vent pipe off the top of the furnace and try again. If it works with the pipe off then there is a restriction in the vent pipe somewhere and needs to be fixed. DO NOT leave the furnace running with this pipe unhooked it is extremely dangerous for you to breath this exhaust in for an extended period of time. If it still doesn't work with the vent pipe off then you need a new pressure switch.
Customer: replied 7 years ago.
well i took the panels off the furnace and wiggled all the wiring and everything around and then it ran constantly for a while, when i put the panels back on it stopped blowing air again until i took the panels off and played with it again, now its running constanly again but what else could it be, is it a possible shorts or is something grounded out?
Expert:  Matthew replied 7 years ago.
Did you clean out this rubber hose on the pressure switch and the hole on the inducer housing where this hose hooks up?
Customer: replied 7 years ago.
i cleaned that out but it was working fine til i put the panels back on it, could it be anything else? theres a switch that gets pressed in when the panels r put back on, i taped it when i had the panels off to see if it would still work and it only works right when i have it taped and the panels off
Expert:  Matthew replied 7 years ago.

This means that the furnace isn't getting sufficient return air and would cut out on limit not pressure switch. This would be a 4 blink code not three. This is caused by a dirty filter which you said is new, a blocked evaporator coil which is the A/C portion that sits on top of the furnace. This is probably the problem because if this is blocked up it will restrict the amount of air you are getting through the vents. When you take the doors off it allows the furnace to pull more air to combat the restriction.

How old is this apartment? if the previous tenants where not good about changing the filter or had animals then the underbelly of this coil probably looks like a blanket.
Customer: replied 7 years ago.
well the apartments r only about 4 years old and maintenance changes the filters, everything works when i have the panels off so im just gonna keep complaining to maintenance til they fix it. i just need it to work so im leaving the panels off it til they can deal with it
Expert:  Matthew replied 7 years ago.

It could be there is not enough return or your exhaust vent is blocked try taking the exhaust pipe off of the top of the furnace and see if it works. Again do not leave it like this it is only for testing the vent function