Central A/C not working properly - hardly any air blowing out

[Jo]

Hello,

The central A/C and heat in my house aren't working properly and I need to figure out why. All the equipment (or whatever you want to call it) is about 24 years old.

The problem started about a month ago when the heat was on. I noticed that hardly any air was blowing out of the vents and the air that was blowing out was cool, not warm. Also, the lights in different rooms would dim every 4 minutes or so. I turned off the heat at this point and notified the owners of the house who happen to be my parents.

I turned on the A/C this morning and the same thing is happening. The lights in different rooms dim every 4 minutes or so and hardly any air is blowing out of the vents. The fan is set to "auto" but everything has been running nonstop since I turned it on over 4 hrs ago, which is not normal. I think it's running nonstop because the house temperature hasn't reached the temperature I set the thermostat to. At this rate, it never will because it's hardly blowing out any air.

My father says he put in a new filter, but this was after the problem started a month ago. He mentioned that the unit might need more Freon, but I think he checked that out because he came back saying he doesn't know what the problem is. He mentioned something about getting someone to check the pressure (whatever that means), but knowing him this could take weeks and I'm burning up.

Does anyone have an any idea as to what might be wrong? And since the lights keep dimming, will that harm any of my electronic equipment, like my computer?

Jo

[Pavel314]

My first thought was a clogged filter, but you took care of that already. The fact that both heating and A/C are bad would rule against the problem being low Freon. If the blower is belt-driven this could be caused by a broken belt. Everything works but the air won't get blown through the house.

What happens at the furnace when the lights dim? Is that when the motor kicks on? And what type of furnace is it, oil or gas?

Paul

[chaniarts]

did the lights also dim before there was a perceived problem? it could something like a siezed fan motor. the motor attempts to kick on, drawing lots of startup power, causing the dimming. the motor then overheats and the thermal fuse shuts it off. when it cools, the process repeats.

yes, the dimming could cause problems with your electronics. they don't like frequent brownouts.

[Ed Pawlowski]

He may have changed the filters, but the coil for t he AC may still be clogged. Since the lights dim every few minutes, I'd guess the blower motor is not working properly and is cycling off and on. There is a set of potential problems such as lack of lubrication in the motor, the blower bearings, belt loose etc.

You need a reputable service tech to check exactly what the problem is. Also, at 24 years, it may be time to look for a new, more efficient AC that will save you money.

[Jo]

The lights used to dim only when something would come on/start every so often. I'm thinking it's when the unit outside would come on that the lights would dim but I'm not sure. But right now, that unit outside (not sure what it's called) is running constantly. It does seem like something is not running and that when the lights dim, that's when it should start running.

I don't know what type of furnace it is, but it's not oil or gas.

Does any of that help narrow things down? We'd like to attempt repairing things ourselves, if possible.

Can anyone give me more information about the dimming and if it would indeed affect my electronics? I have my TVs and computers plugged into surge protectors. But three of my TVs are CRTs and one is LCD, if that makes a difference in anything. I know that my microwave "dims" along with the lights.

Would it be best to just turn the A/C off? It does seem to be keeping the house from get really hot, but I don't want my electronics getting damaged.

[Shaun Eli]

If the compressor (the thing outside) is running constantly you'll be getting a rather large electric bill.

Central A/C units now are at least twice as efficient as they were 20+ years ago so the time it takes to earn back the cost of a replacement unit might not be that many years...

[trader4]

I air isn't blowing out even with the fan set to on, then something is wrong with the air handler. Could be clogged up coils, failed motor, etc. Time for a service call. And with a system that's 24 years old, it should have been replaced last year when you could have gotten a 30% tax credit. A new system would also cut your heating/cooling bills substantially.

[hrhofmann]

If it is not oil or gas, maybe it is a heat pump. You have got to get and provide us with more information for anyone here to be able to give you a coherent answer/suggestion.

[Jo]

This is probably a stupid question, but any idea how much a new system would cost for a 2 story house that's approximately 2400 sq. ft. plus the basement which is about 1400 sq. ft.? I'm just kind of looking for a range, just to get an idea as to how much something like this would cost. I have no idea whether it would be $10,000 or $5,000 or $20,000.

[trader4]

ide quoted text -

There isn't a lot to go on here. We don't even know the climate for the location, fuel, etc. And what a system costs in NYC is going to be different than what it cost 100 miles away in NY state. But assuming it's middle America and just a straight replacement, you should be more in the $5k to $10K range. Many utilities are offering rebates on units that meet certain efficiency standards that can bring down that cost.

[Shaun Eli]

You want a ROUGH estimate? About four years ago I had a 3 ton unit installed (3 tons is the size, not the actual weight of the unit), 16 SEER (that's the energy efficiency, higher # is better) in a 1600 sq foot 2 story house (basement is not air conditioned) in the NYC area for under $13,000. (that was the low bidder and they sucked, I wouldn't make that mistake again- next time I go with a local contractor, not a chain store's clowns).

That price included having to run all the duct work, and that's the very labor-intensive part. The units themselves (compressor, air handler) probably under $5000 plus installation.

But of course you'll have to ask a few contractors for bids, and this is their busy season for A/C (although it'll get busier).

[jamesgangnc]

ide quoted text -

You're getting a mix of advice here, some of it not worth much.

Brownouts will not damage modern electronics.

It sounds like you have a heat pump. It also sounds like the compressor is not able to start. Heat pump (and ac) compressors have an internal thermal overload breaker in them. When it cools down it will try again. There could be any number of reasons why it can't start. It's not likely that anyone over the internet will be able to pinpoint it without directing you to do a number of tests that you probably don't have the equipment or desire to do.

Simply turning the thermostat to the off position will turn the entire system off.

No one will be able to give you an accurate estimate over the internet either but you should be able to replace a complete basic single stage heat pump system (without messing around with the ducts) for something between $2.5k and $5k unless you select more advanced equipment.

[Twayne]

they don't like frequent LONG AND SUSTAINED brownouts. A couple seconds or so won't bother much of anything. Worst case, some of it might turn OFF if it was ON. From the sound of it, if it was going to bother anything you would already know that because it would have happened. A sustained brownout might overheat motors trying to start/run and some electronic things that are turned on might turn off when it hits, but that's about it.

HTH,

Twayne`

[Twayne]

See my previous response about that. BTW, lights dimming could be a sign of a poor Earth ground somewhere, especially if you notice that other lights get brighter on different ckts.

HTH,

Twayne`

[Twayne]

Or it could be electric, too.

[jamesgangnc]

It's very likely the dimming is the compressor trying to start and the cutout engaging. Ac compressors basically start under load so they really can draw a lot of amps initially. 4 minutes is about the right length of time for the cutout to cool and close.

[HeyBub]

Whether the furnace or the AC is working properly is irrelevant to your symptom. You've got a problem with the air handler - the thing that blows the air around. The motor could be bad, the start capacitor could be bad, if it has a belt, the belt could be slipping, the evaporator unit could be clogged with stringy nasties or dozens of dead mice parts, a piece of duct work could have come loose (so that you're cooling the attic!), or any number of mechanical issues.

The good news is that whatever's the problem, it will be easy to spot.

[jamesgangnc]

ide quoted text -

That's a conclusion that I don't think we can draw. Most homeowners don't pay much attention to the volumn of airflow from the vents unless they have a problem. So we don't know that his subjective "hardly any" is a problem or not. Not to say it owuld not be worth while to check the evaporator and airhandler. Almost no air handlers have belts anymore btw.

[HeyBub]

Agreed, but since the problem affects both heating and cooling, it would be really weird for them both to fail simultaneously.

About the belt, you're right. Remember, though, his system is 24 years old (mine's older and it doesn't have a belt), so who knows?

[jamesgangnc]

It sounds a lot like he has heat pump. It failed to heat earlier in the year and now fails to cool. And he is observing the lights dimming at a frequency that suggests a compressor trying to start, tripping the thermal cutout, and then repeating that a few minutes later.