No air coming out of A/C vents in house

15 years ago

Being a new homeowner, this is the first time we have had to use tha A/C in the house. I found there is no air at all coming out of the vents, even though the system itself seems to be working fine. A few facts:

* Outside unit is running; in fact, the line froze from the unit to the siding. I turned the unit off today to allow it to thaw, which it did, but still issues.

* Electric air, gas heat. In the attic the furnace lies next to the air ducts, there is a switch on the wall that turns the furnace and A/C off.

* There was cold air "leaking" from the side of the furnace, which seemed odd to me at least.

* The house sat for a year without being occupied, so I wonder if the vent is somehow blocked.

I read somewhere it could be the air handler. I admit I am a noob to owning an A/C unit, and although I have been successful at fixing other issues around the house as they have arised - many times figuring stuff out as I go - this one has me stumped. Any advice would be appreciated. I am pretty sure the answer is either really simple or really expensive.

Thanks!

Jeremy

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Comments (10)

paulbm
15 years ago
In one place you said you had gas heat and then you talk about a air handler.
So do you have air added to your furnace, or do you have a separate air handler
for your air con. If you have a furnace and a separate air-handler for air con,
are they on the same duct system, Maybe they put a manual damper in there some place that you have to change to go to air con. I have seen silly things like that done. Later paulbm
troys
15 years ago
Check to see if the blower is coming on. Units use 2 speeds for the blower motor one for cooling and one for heating,unless it is a heat pump. If the blower is not running then either the motor is out or the circuit board.
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Need more information. What type of home do you have (1 or 2 story?, 1 furnace or 2, location of furnace(s). If your ductwork is visible, can you trace out where each run goes? Is the 'cold duct' at the end of the trunk run? If you can isolate it,follow the run from the trunk to the register (boot) or where it enters a wall. You may find a leak along the way. Is this a new situation, or was it always like this? V
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Thanks zl700, I think it is probably convection current as it is very mild and mostly coming out the top slots rather than the sides. I didn't see any place in the heat exchanger area where there was any strong air coming out of cracks - it just seemed to be heat radiating from the flames visible at the burners. I also noticed while checking it out that my fan limit controls were set very high - about 115 deg for off and 140 for on. I suspect this was also further heating up the crawl space by keeping more residual heat in the exchanger between cycles. I adjusted them down to 85 for off and 110 for on to scavenge out more heat. I'll probably have it looked at next year after I see how the remodeled house performs over all four seasons. There's also an air conditioner unit above the furnace that hasn't been working or needed in at least 10 years, but with significant changes to the house (roof changed from light to black, stories changed from 1 to 2, more windows) I need to see if A/C is actually needed or not.
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Proviso I'm not an hvac professional. But, at base, it sounds like you've got a pressure differential between the inside/outside of the house or possibly the cold attic - the lower floors are pulling in air because air will move to lower-pressure areas. Trying to track down exactly where the air is coming in from may be a bit of a fool's errand, in that if that pressure differential exists, the lower floor will pull in the air from somewhere - outdoors through doors or windows, or through ductwork from elsewhere. Close off one entirely, you may find it just moves elsewhere. So perhaps focus slightly differently, on what bothers you. Is it the feeling of draftiness due to cold / warm air, affecting comfort? Is temperature okay otherwise? If so, one way to address would potentially be closing partially those vents (with a simple louvre) or redirecting the cold air flow in a different way in the room. (I'm kind of assuming you don't have any other significant issues or complaints about your hvac system). I have had this issue in a few rooms seasonally (note these are not A/C system vents, my heat is hydronic). We felt the draft and was uncomfortable in certain places. We replaced some vent covers with types that partially close or can be redirected. It does not completely block the air, just keeps it from the feeling of draft. Overall it has resolved the issue (and of course important that we did not want to stop the exchange of fresh air, just moderate it some). Note, since you've said it happens differently with windy weather outside, I strongly suspect it is differential pressure within the house (wind blows and there's all kinds of effects of faster air/lower pressure around the house). It's possible there are other ways to address such as improving air flow within the conditioned space (so instead of cold air moving to reduce the pressure imbalance, it's warmer air doing so). But this is a hideously complex subject where the house has to be looked at as a system and I'm not going to guess how to do this or diagnose over internet. Oh, another small thought - why did you turn off the fresh air system? What is that system? It's possible this is part of the issue, that the fresh air system was partially intended or designed to help deal with/moderate the pressure imbalances. Did this problem start occurring more when you stopped using that system?
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brickeyee
15 years ago
Sounds like the evaporator coil may have frozen up with ice.
It will block the airflow very nicely.

Have an AC technician come and check the system out.
Ask neighbors for recommendations.

The system could very well be low on refrigerant.

Do not try and run it, especially if ice is forming al the way to the outside compressor.
If refrigerant liquid gets back to the compressor it will be destroyed.
troys
15 years ago
If it freezes right after it starts it is a airflow issue not freon unless the coil is already frozen. If it takes several minutes or hours then it is probally a charge issue.
scotkight
15 years ago
Or the humidity could be VERY high, or you have an open window or three (combined with high humidity). Or the drain from the evaporator could be blocked.

Turn on the fan, but leave AC off to melt ice off the evaporator and make sure all of your windows and doors are closed. Some newbies (myself included) have left a few windows open before while trying to get the heat out, and turn on ac to get the temp down. That combo doesn't really work well :)

Make sure you see water trickling out of the drain. If not, thats a problem. If the piping feels lukewarm (not hot or cold, depending on where you touch it) something ain't right.
brickeyee
15 years ago
"Or the humidity could be VERY high..."

A correctly operating system should still not be frosint to the condenser.

An open window might limit cooling, but the drop across the coil (and air flow) should still be there.
donniehvac
15 years ago
First things first folks. Check the air filter, it could be plugged. Frozen coils come from these things: dirty air filter, low refrigerant levels, inadequate airflow (motor failure, motor ineffiency, blower wheel problems). That's pretty much it. The filter you can check yourself. Refrigerant levels, motor/ blower issues should be taken care of by a reputable service company. Good luck.
trod0214
13 years ago
I live in a double-wide home. I have noticed that not all the vents are blowing out air. Some rooms with vents have the air coming out pretty good and other rooms hardly have or don't have any air coming out at all. Can anyone help?
izzysremodeling_aol_com
12 years ago
unit freezes up over nite or at cooler temps, but will run all day without any probs when its hot, pessures are fine freon is fine filter is clean fan working properly, any help would be great thanks in advance
dsyauger_att_net
12 years ago
Thank you donniehvac!!! I followed your suggestion on checking the filter and turns out, it was very dirty. I'm very good about changing the filter monthly but I guess I underestimated how much dirt had accumulated. I turned off the AC altogether for about 4 hrs to let the unit thaw out. Turned it back on and ta-da!!! I had cool air again!!! You saved me what could have been a costly service call. It pays to research the web before calling for service. Thank you again!!

No air coming out of A/C vents in house

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paulbm

troys

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