View Full Version : Help! AC Stops Blowing Thru Vents?
I've got a problem with my home's air conditioning unit that I was hoping I could get some suggestions on, regarding where to start. I'm a rookie at this but did manage to replace my inducer blower when the heat died over the winter.
What's happening now is I turned on the AC for the first time this season. Both outdoor blower and indoor unit fan seem to be running fine. I got cool air out of the vents, but in a few hours, the airflow through the house vents just stopped. Downstairs, I could still feel cooled air seeping out through the edges of the ducts at the unit itself, it's just as if the fan is being blocked from passing air from the main unit up into the house somehow.
The next day, I turned just the fan on without any heat or ac, and the fan blew air through the vents all day. I also tried heat with similar results. The ducts only eventually seem to stop blowing air when I turn on the AC (after a few hours).
The cooling in general, when the air WAS blowing, seemed a bit inefficient, slower than past years.
Does anyone have any ideas where I can start here? I am a rookie DIY'er but a good student. Of course, if this is an advanced issue that I will need to call in a repair for, let me know that as well. I am worried there may be a freon leak that is somehow blocking an air vent/line as the AC cools down.
Thanks for any assistance.
05-15-2007, 10:44 AM
I think you have a refrigerant leak and the system is low. This can cause the evaporator to ice up, which restricts air flow. When this happens, take off the access panel and check. I think the fan motor will be happily churning along...my guess the evaporator is covered in ice, blocking the air. The evaporator coils are the part that is in the air duct - usually on top of the furnace; if you have an air handler, it is inside of that. In my limited experience, when they start to leak, unless you can find a fitting that has a problem where you can fix it easily, it may end up being time to think about replacement, since it is probably the compressor or the evaporator coil.
05-15-2007, 10:45 AM
Have you done any preventive maint. yet: Clean off any debris from outside of unit that could be blocking airflow. Replace air filter, and clean coils.
If your air filter is covered with ice, that indicates a large freon leak, and you need to fix it right away.
You probably need a freon recharge anyway, if the air itself isn't as cool as in prior years. That would indicate a smaller freon leak, which they should find as well.
Note: unless you are certified, it is illegal for you to do anything involving freon.
05-15-2007, 06:56 PM
A lower VOLUME of air flowing over the evaporator could also cause it to ice up. You said you replaced the (inducer?) blower this past winter. Could you be more specific? Is it possible you have a lower RPM on the blower, and hence less volume of air flow over the evap coil, than you did last year?
When the flow stops, remove the filter and check the AC coil to see if it is iced over, which is what your description seems to imply.
If by air filter you guys just mean the removable sheet filter that goes inside the HVAC unit, I just took it out right now to eliminate it as a factor. I replaced it pretty recently, anyway.
It got weirder yesterday -- I had the AC on all day and it took about 7 hours to cool the house down by about 5 degrees from 77 to 72 -- The air feels cold coming out of the vents but airflow just generally seems a bit less. Last weekend when I ran the AC overnight the flow had stopped by the morning -- This morning, go figure, I still am getting airflow from the vents.
But -- Is it normal to feel so much cold air escaping along the ductwork that runs up alongside the indoor unit? I don't recall that much air there and think this may be a result of a partial blockage somewhere (perhaps this icing over you guys are talking about). Which may explain why it's taking so much longer to cool the house and why the AC continues to have to work so hard to KEEP it cool. It's not that warm here in PA yet.
I placed a photo here:
AC Photo (http://www.newsaskew.com/a)
That's my indoor unit. The black plastic part near the bottom is the inducer blower. I'm not sure if this runs with AC or only heat.
Sorry for all the novice questions -- Where do I find the AC coil that you guys are suggesting might be freezing over?
Now that it's working again, I'm less inclined to call in an expert to look at it, though it's been 8 years since I bought the house (new) and it's never been looked at or serviced, so maybe it's just time?
05-16-2007, 09:01 AM
Follow the refrigerant lines from the compressor. They connect to the coils. Probably above the furnace in the duct, but could be elsewhere.
05-16-2007, 10:43 AM
The ice should be obvious if you removed the air filter. The coil that usually ices is the inside evaporator coil (that the air filter rests against.) By now, most of your freon has escaped I think, so you may not see any icing.
If you have an air thermometer, test the temperature of the air coming out of the vents. It should be 15-20 degrees cooler than the room temp, if everything is working properly. Also, the copper pipes coming out of the compressor should be cold and sweating (like a cold beer can at the beech).
One other thing. Look for the return air vent. It should be the biggest and lowest vent near your unit. If it is blocked by furniture or covered with dust, that can restrict air flow as well. As can the little fuzzys that collect on the outside coil of the unit. You must hose those off.
05-16-2007, 11:02 AM
Depending on the layout of your AC/furnace, the ice may or may not be visible even with the filter out. It wasn't on mine when it started to ice up.
Another way to test for icing: Next time the airflow goes down, turn off the AC, but keep the fan running. Over the next hour or so, monitor the water coming out of the AC condensate drain (it should increase dramatically), and monitor the airflow coming out of the vents (it should also dramatically increase, as the ice melts).
Thanks for taking the time to respond, everyone.
I may be in a bit over my head here, as I don't have a clue where to find the AC coils, compressor, condensate drain, etc. I know absolutely nothing about the makeup of the unit itself. I learned the bare minimum to replace the inducer blower fan which you see in that photo below, but haven't taken any other access panels off and have no idea where to look for the other stuff. I'm sure you guys are right, and that I'd be able to find the issue, but even so, if it winds up being something more complicated that just disconnecting and rewiring a new replacement part, I may need to call a pro in anyway...
I'll see what pieces I can get apart in the meantime, though this one might be a little much for a DIYer like me...
05-23-2007, 10:29 AM
I don't think you're understanding what's been said here.
There are a few simple things you can do to help troubleshoot the problem. You can hose off the coils on the outside of the unit where all those fuzzy tree seeds collect and block your air flow. You can clean off your intake air vent that is near your unit in the inside of the house. You can use an air thermometer to measure the temp of the air coming out of the vents. You can remove and replace the air filter and look for signs of icing. You can look at and feel the 1/2" copper pipes inside the unit to see if they are sweating and cold, or if they are warm. You can listen to hear if the compressor goes on. and wait to see if it goes off again before your house is cooled.
Once you've done this, you can report the info back to us so we can further advise you. Keep in mind, only a certified A/C tech is allowed to remove/add freon to the system.
You can also try posting a photo on this site, because your photo is on a "forbidden" server.
What is the make of your A/C unit? Is it a furnace and A/C combo?
Verdeboy - Thanks. :)
The outside unit is clean, I do clean it regularly. Also, remember that for around the first 4-6 hours I turn on the AC, it does cool the house and the vents blow normally. I also feel the warm air being blown outside from the unit at this time as well. It is only after around 6 hours or so of constant running (trying to cool the house down around 10 degrees or so) that it stops blowing through the vents. So this does seem to indicate something freezing up. Otherwise, I would think it would not blow cool air at all, even when I first turn it on...Or am I mistaken?
I was unaware the photo was on a forbidden server. I'll post a better pic as soon as I get home from work. The indoor unit is by Ducane and it is one tall unit that handles both the heating and cooling (combo). The unit was brand new when I bought my house (new build) 8 years ago. I have not done any special cleanings or service on the unit since, though.
I removed the air filter I placed inside the indoor unit (which I change regularly) and there was no ice buildup.
I don't own an air thermometer, is there a good spot I can quick grab one? What is the air temperature from the vents supposed to be, typically?
Thanks, I'll post a better photo in a few hours.
05-23-2007, 01:21 PM
You can buy a thermometer at any drug store, hardware store, etc..
The air coming out of the vents should be 15-20 degrees cooler than the ambient room temp. And it should be coming out at a decent velocity.
As I mentioned, the pipes coming out of the compressor should be cold to the touch and "sweating", if all is working properly. It sounds like the compressor may be overheating and shutting off prematurely. This could be due to a number of factors including icing.
There should be a little drain pipe coming out of the bottom of your A/C. This is your condensate drain. It may be tied into another drain or it might just go through the wall and drain outside. Look for a pipe sticking out of the wall near the outside part of your A/C. Do the test that Steve W. mentioned: After the cold air stops coming out, go to the thermostat and turn the A/C off but turn the fan on. Watch for an increase of water coming out of that pipe.
05-23-2007, 01:57 PM
The cooling coil is often placed on top of the furnace in the ductwork, if it is, then you can't see the coils from where the air filter is. As noted, follow the two lines from the compressor (the part outside) and see where they go. They connect to the cooling coils. My guess is that they are getting blocked by ice. This is a gradual process that could take hours, depending on conditions.
There will also be a drain line coming from underneath the cooling coils. Depending on setup, this may flow to a pump or directly into a drain, or outside of the house. When the a/c is operating, there should be at least some water coming out of this as well.
You guys pretty much got it right. I just had to learn where everything was. I found the lines from the compressor, and both were extremely frosted over in their exposed parts, both inside AND outside of the house. I didn't need to open the top plate to know that the coil was icing over, over a period of enough hours.
So, I let the tech come over figuring this was not something I was going to be able to do on my own. Sure enough, he hooked up his meter and the freon or R-22 or whatever it's called was reading 15. I've got a leak. He said it SHOULD read 40.
But here was the sad part -- He said he can't tell where the leak is today, he could only fill it back up with new stuff, also adding in a special dye. Then, over time, it WILL leak again and then they can use the dye to determine where. He tells me depending on the size of the leak, it can be anywhere from a few months to a few years until I am low again.
Here's the thing though - This all cost me $567! Does that sound right to you guys? Almost $100 per pound of the juice plus the dye was another $100 plus the service, etc. Charges like this are why I hate service calls, though I realize sometimes there is no other option.
The other bother is he tells me that he guesses it's the inside coil but can't be certain, so can't fix that today. When he DOES fix it he's guessing around $1500 total parts and labor. Does that sound right as well? Seems awfully pricey. Not to mention, I'm going to have to pay AGAIN to refill it as his advice was just to let it leak out until it's low again.
I'm thinking I want to buy a couple things and monitor this leak myself. First, is there anywhere I can get a meter like his to hook into my outside unit so I can read the levels of coolant in there? I want to see how fast down it's dropping from 40. Also thinking of then getting a black light as he advised so I can determine where the dye is leaking from.
Anyway, $567 later and it's not even fixed. Just a band-aid. Did I get railroaded or is this just the way it is?
05-24-2007, 02:32 PM
This is heresay, I do not know if it is true...I thought that it was illegal to refill a system where it had a known leak without fixing it first.
They make leak detectors, but I don't know how well they work. If he ran one over the system but did not discover a leak, he may have met the intent of the law...a really slow leak might not register unless the equipment was really good.
Start budgeting now to replace the thing - both the internal coil and the external compressor. The new ones are likely to be much more efficient than the old one you have. When I replaced mine awhile ago, my electric bill went down $60/month, and I have a small townhouse (but out electric rates are some of the highest in the country). Not that that would repay for the replacement, but it will probably come close to when it needs it the next time. The new refrigerants are less costly as well.
05-24-2007, 05:35 PM
I completely agree with Jim. Same thing happened to me a few years back - a leak showed up. We patched it once, and it held for a year or two, then another leak showed up. The HVAC company recommended replacement of both evaporator and outside unit, AND the tubing connecting them. We did, and took the opportunity to put in a heat pump.
By the way, when you do replace your outside unit, spend a little more and get a "scroll" compressor. MUCH quieter than the other kind, and I think they last longer, too.
Thanks for the input, guys -- I'll start saving up.
Any makes/models I should go for? I don't plan on being here at this place for many more years, it's my first house and I plan to upgrade in the next 5 years, give or take -- So really I'm just looking for a good budget model that works.
What price I am looking at for all this stuff? Are you guys suggesting replacing the entire system, both indoor AND outdoor units?
By the way, oddly enough the AC seemed to cool the place much better when it was low and the line was all frosty -- It's been running for 3 hours now and the temps actually went UP a degree from 75 to 76 instead of of down 72 like I have it set...Weird. Before he fixed it, the house was cooling down in a few hours. There's cold air coming from the vents (some are blowing much better than others) and hot air venting from the outside unit.
Oh, one last question -- Should the air filter be practically getting sucked into the fan inside the base of the unit there when I put it in? I just went to change it and I swear I never thought it pulled that much before. Also, there's a lot of cool air seeping up along the ductwork to the left of the indoor unit...Is that normal guys? Again, never noticed before since I never had it problem, it may have always done this.
05-24-2007, 06:29 PM
You mentioned that you replaced the fan. Those are often available with multiple speeds depending on how you wire them up. You may be running the fan faster than needed. This means that the air doesn't dry out as much or cool off as much as it passes through the coils. It also costs more to run. You may need to slow it down. If you saved the instructions you might have a means to adjust it. This is all part of designing and maintaining a properly sized system and you can get into performance and cost issues if you don't maintain it properly. If it is a higher end furnace, the speed control could be controlled by a circuit board or a switch.
Actually I replaced the inducer blower for the heater, which I was told today by the tech has nothing to do with the AC -- It's a gas heater, not a heat pump. I don't think that part even comes into play.
I guess I'll give it the night and see. It feels really humid in here and I never recalled it taking this long to cool the place down before -- The vents are blowing cool air, most of them at a decent rate, and the outdoor unit is blowing hot air as I expected, so I'm not sure wassup.
Any idea how long it should take to cool the average house when the AC is turned on for the first time? I figure it was cooling extra fast before the fluid replacement because when the air was blowing, it was blowing through an iced coil, which made it VERY cold. ;)
05-24-2007, 06:56 PM
R22 is about $3 a pound wholesale, but of course has to mark that up a little, and he does have to pay a disposal fee when he pumps your system down. I don't have an EPA cert. and I don't know if it is OK to pump up the system and "come back later " to check for leaks.
You cannot mess with that system, because the EPA fine is $10,000 for uncertified people messing with refrigerant.
I do not like some of the other symptoms you describe....the filter getting sucked up , etc. You might need a tech ( different one) to look the system over real good at the time you spring for new 13 SEER units.
I don't like it much, either.
The tech said if I'm not happy with the service to call back and they'll at least come back out and check it again without charge. So I may as well call the same place again, at least it wouldn't cost me anything to have them come out.
This is also why I hate looking for techs, I think I just picked the wrong place -- The shop I called is a local jack of all trades shop, sent out one of their HVAC specialists that turned out to be a kid just a few years out of tech school. Sigh. Obviously he did what he thought would remedy the problem but didn't think to check anything else out.
I'm sitting in the house, the AC has been running now for 4 hours and the temperature has gone up a degree since I turned it on in the house. The baffling thing is that the vent I am at IS blowing cold air (maybe not cold enough though, I dunno).
Not sure where to go from here really. So in charging me $100 per pound for the R22 are you telling me I was WAY overcharged? Or is that just the industry standard for most shops?
You know, the more I think about it, the air that's coming out of the vent is cool, but certainly not COLD -- It was much colder before he added the R22 today (no idea why adding R22 would make it wamer, though he did say my system was using a different type of coolant that they don't use any longer). So I guess I'll call them tomorrow and see if they can send someone back out for free to do a better diagnosis.
The problem I have with this $80 to show up at the door policy that all these HVAC contractors have is that it basically forces you to use their services once they show up, unless you want to pay another $80 to get another contractor to come out and diagnose and give an estimate. Makes me wonder why the ads say "free estimate" when it's really an $80 estimate.
05-24-2007, 08:21 PM
I do believe they should be more clear about the Free Estimate. Apparently they give you an estimate on the phone? $80 to take a look. If you call them out, then you pay the $80?
I am now also concerned when you say it used to have a "different refrigerant". For the most part, you cannot just add another refrigerant. In general, I don't think you can mix types. Again, you are talking to mostly plumbers here, not HVAC experts. I have some basic knowledge and am trying to look for "issues" and point you in a direction.
Wow, that's really interesting Jimbo. I can't help but wonder if the guy may have screwed the system up by doing that, then. I know he said something about my system using a refrigerant that they don't use anymore, and needing to put R-22 in...But I can say with certainty that he didn't drain any of the old stuff out before he did this. I watched him hook the tank up to the existing system and just turn it on to fill it back up.
Needless to say, I'm calling them as soon as they open this morning. If any major work needs done, I don't think I want this company doing it, though I think they at least owe me a free service call to come back out and re-diagnose the problem, hopefully the proper way this time.
Thanks. If anyone else has anything to add I'm all ears. Thanks, I am learning quite a bit here.
I think the Serial # / Model # tag should have the refrigerant # stamped on it.
I wonder if it is and old unit that takes R12 and he dumped R22 into it. If he did they need to evacuate all the refrigerant out and recharge the unit at no cost to you.
If yours needed 134A and all he had was 22. I think 134A is a blend and maybe he thought the 22 wouldn't affect it. I would look for the tag and see if it has the type of refrigerant needed stamped on it.
Cass, thanks for that option -- Do you know where the tag might be located? Somewhere on the outdoor unit or would it be inside? If I can locate that on my lunch hour today, I can post up what it says it needs. My unit was new 8 years ago, so who knows what fluid that took, but he didn't seem to do anything but assume R22 without further study, so you may be on to something here.
Could it be possible than an 8 year old unit took R12 or 134A?
05-25-2007, 09:17 AM
I'm not sure when the switchover was. The tag would be on or inside of the compressor unit (the part outside). It might be visible without taking the service cover off. It should also be in the servicing info which should have been left with you.
05-25-2007, 09:18 AM
8 years ago it is not likely anything but R22. R134a is not used in residential , as far as I remember. It is a replacement for R12 in autos. The current "new generation" refrigerant is R410. And I repeat that in general, you do NOT mix refrigerant types. Now, there may be exceptions to this because again I am not an HVAC tech. I know just enough to be dangerous, as the saying goes!
It is important to note that you do not "drain out the old refrigerant". That would bring the EPA down on you. It must be pumped out using a vacuum pump and refrigerant recovery system. Together, these two pieces of equipment will set you back a minimum of $700 and a better set you would be in the $2000 range. Not to mention a few hundred for a good set of gauges and hoses. Not to mention they have to pay to dispose of the recovered material. The EPA training and cert. is also not free. So you see some of the reason these guys do charge a lot.
Anyway, I think we have enough flags here to seek a second opinion from another service company.
Thanks -- I still haven't heard back from the original contractor regarding coming back to troubleshoot the problem for free - My plan is still to let them come back just to hear what they say, then get a second opinion from another contractor. I also want to get some good solid advice, depending on the problem, on replacing the entire system vs. just fixing the problem. If it's $1500 to repair it or $2500 to replace it entirely, I may lean towards just replacing it all to ensure (hopefully) more trouble-free years and no more breakdowns (seems that often when one part goes, others follow).
05-25-2007, 12:34 PM
I don't even know where to begin here.
First of all, you still don't even know what the problem is. They charged you over $500, and you are way worse off than when you started. They need to troubleshoot and fix the original leak, as well as pump out and recover the entire system of all of the mixed refrigerants.
The dye should only be used as a last resort. A relatively large leak can be eyeballed. You just turn the A/C on and look to see where the ice first starts to form. And there's your leak. I don't think it's an extremely slow leak or you wouldn't get so much icing. You may, however, have 2 separate problems. You could have a very slow leak, which would account for the low pressure reading. The icing may be due to something else entirely.
Regarding the service tech: Even if he was stupid enough to mix the refrigerants, he still should have noticed it wasn't blowing cold air. And he should have called back to the shop for guidance.
If they tell you that you need a new compressor or something else very expensive, then you should find out the cost, minus what you've already paid them in order to make your decision.
If they give you a hard time, you should threaten to sue and notify the better business bureau.
05-25-2007, 12:55 PM
A natural result of low refrigerant is icing in the evaporator, it is not caused by it leaking refrigerant directly. Not moving the right amount of air over the coils can result in some, too, but that is not his problem.
I had my compressor replaced last year...did not replace the evaporator coils or lines, the old one was a 14 SEER, replaced with a similar unit - cost me around $4k. Depending on where you live, and what you have, labor rates and the price of the unit will differ, higher or lower. Our labor rates are above average, but not at the top tier as seen in some places.
Here's the update -- Got a different tech this time, a much more confident one who obviously had a ton more experience. Really nice guy. He immediately made me feel more confident about things.
He looked over the entire system in detail then we went out back, where the outdoor unit (compressor is it?) was making a horrible noise. He hooked up his gagues to realize the system had been LOADED with R22. Like WAY overloaded. The gague was going through the roof. So he let me know I'd be refunded everything except the original service charge to come out, and no charges at all for today. Completely sucked the system dry and then refilled with the proper amount of R22 for the system.
He said he didn't actually detect any leaks, or think the system even had any, and didn't see any reason why it would have iced up. So I'll be keeping a close eye on it the next few days. He did show me that my inside coil was pretty corroded from 8 years of usage. Also, my outside unit is not in the best of shape either, efficiency-wise. A very stupid person (read: me) tried to clean it 2 years ago with a pressure washer. I got about halfway done before I realized I was pinching the fins closed. So the unit has been working very hard but has cooled well for the past 2 years. I realize its days are numbered.
In the end, he admitted that the last tech made a lot of mistakes, the key being not letting the coil defrost before service -- He didn't say anything about mixing coolants, or the dye, but he DID say that he needed to let the coils inside defrost before hooking up the machine to get the coolant reading -- He didn't. Hence the reason he was able to extremely overfill the system. I asked if this could have damaged anything and his reply was no. I imagine if I want to be a really squeaky wheel about it I could complain and get free service or parts, but the guy was nice and spent a good 3 hours with the system and I at least have had a good checkup on it and new R22. We'll see how cool the house gets tonight, of course.
They did quote me a bit over $4k installed for an entire new system from Trane - Or something like $330 for a full cleaning of the system, inside and out. I didn't accept either. Think I'll still go with another company (or at least get another estimate) before replacing anything, parts-wise or system-wise. The GOOD news of all this is at least I am not out close to $600, and can go back to square one as far as finding a good contractor to ultimately fix whatever the problem is.
What a day.
05-25-2007, 04:17 PM
If you go to a hvac supply shop, you can buy a comb and straighten the fins. This will help, and won't hurt. They come in various pitches, sometimes on different sides of the same tool to match the spacing of the originals.
06-09-2007, 04:36 PM
Not to derail but anyway on cleaning the coil? Seems the outside is clean but I wonder on the A coil the underside? Seems that would get the dust that the filter missed and could limit the amount of air transfer.