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-   -   HVAC not blowing out of vents (http://www.diychatroom.com/f17/hvac-not-blowing-out-vents-148101/)

autx790 06-24-2012 02:33 PM

HVAC not blowing out of vents
 
I noticed yesterday that my temperature in the house was higher than what the thermostat was set to. It indicated the AC was on, and the fan was blowing outside, but no air is coming out of the vents. It seems that even though the fan is running outside, the return air is not pulling air. Can anyone guide me to where I should start troubleshooting?

Thanks!

Update: I looked inside the unit and even though it doesn't feel like there is air being pulled at the return grill, the blower inside the unit outside is on and pulling a good bit of air. It seems the condensor (i think...black cylinder under the fan with two copper pipes attached) is freezing over as are the coils. Is this a low refridgerant problem? It was working great until yesterday, it just stopped blowing air.

JJboy 06-24-2012 03:05 PM

1- Check if Blower Fan is running. If it running ok....turn off AC and leave only Fan on.....A-coil is frozen.
2- Check all return filters are clean.
3- Check for small leak.

autx790 06-24-2012 03:58 PM

Hey JJ boy, thaks for the tips. The filter is brand new. I've had the blower running for about an hour. How long should i let it sit before turning the AC back on? If i turn it on and it freezes again, does that mean it's probably low on refridgerant? I dont see a leak, but if it's low i'm guess there would have to be one, right?

JJboy 06-24-2012 04:10 PM

Yes, leave fan on more time......Next time you turn on the AC check if is getting good air flow at the supply registers but warm air.....The refrigerant is low

The best way to check for small leak is pressurise with nitrogen at 150PSI and leave all night under pressure

beenthere 06-24-2012 04:42 PM

I usually tell people 3 to 4 hours with just the fan running to thaw a coil.

bbo 06-24-2012 04:43 PM

leave the fan on overnight.

there should also be a drain line for the AC unit, make sure this is not plugged. if it is, it'll just freeze right back up when you turn the AC on.

unless you have the means to check the refrigerant, ( ie pull it out and weigh it) you'll likely not be able to diagnose low refrigerant.

biggles 06-24-2012 04:49 PM

did you leave it on all night and did it get a little cool outside overnight?the ice always starts at the air handler then works it way out into the condenser and covers the compressor.if have ice forming on that insulated line coming out of the air handler the coil is icing up and air is being retricted and gets as you feel nothing out of the vents...so the filter is good supply fan squirrel fin/rounds are clean

autx790 06-24-2012 06:42 PM

Thanks guys. I left the fan running for 3-4 hours and now i try it again. I get a tiny bit of cold air coming out of the vents closest to the unit, but at the front of the house where the return grill is, there is pretty much no air still. The return air doesn't appear to be sucking near what it used to. I hear/feal nothing. I guess i'll leave the fan running over night and then give the AC people a call in the morning.

On the unit outside there is a opening going out of the unit and it is not obstructed so water drains out.

beenthere 06-24-2012 06:44 PM

Could be a dirty indoor coil, or bad/weak capacitor.

autx790 06-24-2012 06:45 PM

actually, in the time it took me to write that post, the unit is completely froze over again. Everything was covered in ice.

autx790 06-25-2012 01:56 PM

The AC tech just left and it turns out, i'm not low on coolant, and the evaporator coil is clean. So his guess is there is something stopping up the return duct, but I just dont see what could do that (it's a big trunk). They're going to have someone else come out to take a look at the duct work.

Doc Holliday 06-25-2012 02:30 PM

Completely ridiculous they didn't take care of this right then and there, especially for something as easy as opening up a trunk line.

Insulation has been known to drop from the inside of air handlers and stick onto the coil or from the coil itself.

autx790 06-25-2012 02:41 PM

Hey Doc, what's ridiculous is him charging me $89 to tell me someone else will have to figure it out. On my unit it's all together outside and you have to take the top off to get to the evaporator coils. There wasn't insulation or anything blocking the coils, but it was hanging a little in the blower box and looked to be a little damp. he just pulled it out and through it out. He said it wouldn't hurt anything not replacing it. I'm guessing however that the insulation was there for a reason and had a foil facing for a reason too, and now there is a little insulation left but the foil is gone.

I will say whatever the problem, it's completely blocking. If flow rate was a measured scale from 0-100, then before it freezes over (which takes 5 min or less) im at about 7.

Doc Holliday 06-25-2012 02:48 PM

I was just going to say I hope you didn't pay him, but at the last second deleted it from my previous post. Too late now but you should've said you'll pay once the other guy comes out and at the very lest finds the problem.

You have a pckage unit? It could be a collapsed trunk somewhere or simply a hole in the trunk line as well as or either insulation stuck somewhere BUT if it was insulation than 99% sure it would have been sucked up and into the evaporator which all you need to do is remove a few panels to get to on a package unit.

autx790 06-25-2012 02:52 PM

Well that was the charge, but I'm not having to pay till they get it resolved.

On my unit the whole top comes up and that's how you get to the evaporator. It's an old (2007) Goodman. Though it looks a lot older. I'm not sure how a truck would collapse cause it was working just fine saturday morning, and then just stopped. I'm hoping some part of the house didn't drop down on it. But hopefully i'd notice that :) There is no air coming out of the registers, but if you open the side panel of the unit where the blower is, then you will get air flow. At least that's what he said...I hadn't tried that yesterday.


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