How to troubleshoot weak A/C?

[Flyover]

Here in central Oh Hah it's been in the 80s/90s outside plus humidity, and our A/C is having trouble keeping up. It's slightly cooling the house (single story ranch with a crawlspace) relative to how it feels outside, but not by all that much, and during the day the house basically never gets down to the 73 degrees we program it for. (The inside thermometer on the thermostat usually reads between 80 and 83; I have no idea if that's accurate, but it feels not-cool-enough inside, anyway.) The fan in the outside unit seems to be working, and air is moving through the furnace. I changed the air filter recently.

In other words, at first glance nothing seems to be broken. And like I said, the system works, it's just weak. So what's the problem? What can I do about it?

I haven't gone down into the crawlspace to check if any ducts have come loose, so I'll have to try that. Any other ideas besides that? Or are my expectations of my A/C system just too high?

 

[Fireguy5674]

Are your coils on the outside compressor unit clean? If not use the garden hose and clean any grass, leaves or other gunk off. How old is your unit? Unfortunately, they wear out. Have you had the Freon levels checked? If it has developed a small leak and the gas levels are low it will not cool properly. Is the compressor running in the outside unit and not just the fan? It sounds like a low Freon (or whatever gas you have) situation. Without more info it is hard to say. And without a set of gauges and some basic knowledge of their use there is no way to tell for sure. How long have you lived there? If it cooled the house last year, it obviously should be doing it this year. Sorry, more questions than anything I know, but all questions that need to be answered.

 

[Flyover]

.

>> Are your coils on the outside compressor unit clean?
I have no idea. I haven't deliberately cleaned them, although we do make sure to keep vegetation and other obstructions away from the unit, and it's not in a location where a lot of leaves or grass clippings fly onto it. Guess I'll look up where the coils are and how to safely spray them off. (Unless it's so easy you can just tell me... )

>> How old is your unit?
Don't remember. I know it's not past its estimated lifespan, but it's definitely not less than 5 or 7 years old either. I'll have to look at the inspection report.

>> Have you had the Freon levels checked?
No. How do I check them? If the levels are low, does that necessarily mean a leak, or do the levels naturally go down over time? If it's a leak, is there a simple repair or replacement I can do to fix it?

>> Is the compressor running in the outside unit and not just the fan?
Not sure. How can I tell? I do feel cold air blowing when the A/C's on, so the compressor must be doing something, right?

>> How long have you lived there?
Almost exactly two years. This is our third summer in the house, and I'm pretty sure the A/C worked better the past two summers. But maybe this summer is also just hotter? I dunno.

 

[Fireguy5674]

>>The coils on the compressor unit outside have air being pulled though them constantly when the unit is running. Because of that they draw in dust and dirt continuously. Use a garden hose and spray the coils off to remove any accumulation of dirt and gunk (scientific term). If possible, spray the water from inside the coil to the outside. All components are water tight so you will not cause any problems by doing this. For safety shut off the power to the unit since there is live electricity going to it.

>>You cannot check the Freon level in your unit without a set of gauges specifically designed for that purpose. And those pressures are critical to the proper operation of your unit. A/C units work by compressing the Freon gas to a liquid and sending that liquid to a coil in the plenum of your furnace. There the liquid flashes to a gas and absorbs heat from the air to get the energy to that. It then returns to the compressor unit outside to release that heat as it is compressed back to a liquid. If there is inadequate gas in the system to move enough heat, your house will not cool properly. I do almost all of my own repair work around the house, but I do not own the gauges or gas to do this because it is cost prohibitive to do so based on number of times it is required. If there is a very small pinhole leak somewhere which has allowed the system to lose Freon it will be hard to find and will need to be silver soldered shut.

>>If you are getting some cool air inside the house the compressor outside is probably running. The best way to tell is to stand next to the unit and listen carefully when the unit starts. You might also be able to see the compressor move slightly on its rubber mounts when it starts. The compressor itself is a sealed unit, usually black with wires and tubing running to it.

>> If the unit is sized correctly it should have no problem cooling the house in the conditions you described. Bottom line, in my opinion, you need to call a reputable A/C Technician and have them check the system. Your description of the problem says to me you are low on Freon. I am a long way from the unit, but if I was a betting man, I'd be looking at that first.

Hope this helps. Probably not what you wanted to hear, but it is what I would do.
Know anybody who does A/C work?

 

[Flyover]

I'll start with the thing I can do myself, I guess (spray off the coils), then think about who I might know who can check the freon levels/do repairs if necessary. Thanks for that info!

 

[Flyover]

OK, the coils are sprayed! I hope I did a good job...I have the kind of unit where the coils are covered by downward-sloped vents. First I took the top part with the fan assembly off and sprayed from the inside out. A lot of gunk and debris flew out, but a lot clung to the vents. Then I sprayed laterally across the front of the vents, and that got most of the rest of the gunk and debris off. I was somewhat systematic about making sure each slat and each column got a good spraying. Then I put the top back on and plugged the fuse back in. We'll see how that goes...

 

[Johnboy555]

Fireguy seems to have it covered. My guess would be low Freon. Usually at the beginning of the season the A/C guys have "Tune up specials" for reasonable rates. I have them come out every 3-4 years just to keep things right. Ask neighbors for recommendations. I really hate just calling someone out of the Yellow Pages.
Of all the services I do (40+ years) I have never gotten into A/C or refrigeration.
Good luck!

 

[Michael Armstrong]

A little late for OP, I guess, but a caution for others: Don't use a pressure washer to clean the coils, even though it may seem like a good way to blast off the sticky debris. The high-pressure water will deform the fins and severely limit airflow.

 

[Fireguy5674]

Sounds like you did a good job on the compressor coils. Even if you have to have an A/C tech out, they would have cleaned the coils before checking pressures because it effects pressure readings if they are dirty. May even help your indoor temperature some. If nothing else it should save some time you would have been paying for.

 

[Flyover]

Is it cheaper to have an A/C guy out when it's cooler out, like in October or November? Or is it more expensive?

 

[WyrTwister]

As it gets cooler , in the fall , I have always read that some HVAC shops slow dawn and may drop prices some . To compensate & drum up business ( and cash flow ) .

I have been told , in our area , they HVAC shops do not have anywhere as much business in the heating season , as they do in the cooling season .

Do not know if I have helped you any . Can you DIY the work ?

By the way , the question was asked , about leaks . The A/C system is suppose to be a sealed system . If the equipment is installed correctly / carefully & all the brazed connections / joints are done professionally , it should never leak . Unless come component breaks or develops a split / crack . Refrigerant & the refrigeration oil are not consumed by the equipment , while it is operating .

To check the system , you need a set of hoses / gauges and a fair amount of education . And more tooling and possibly some refrigerant . Which you may / probably can not purchase with out an EPA card .

Best of luck to you ,
Wyr
Gd bless

 

[user 4883]

Spring time is booked with startups and preventive maintenance.
Summer is booked with repair/replacements.
Fall is slow but, you want to have your system checked during the summer when it's hot out.
This will give you the best pressure readings to tune your system.
Systems are sealed but prone to leakage. Some can be "topped off" after years install and not have a problem for years. Some need leak repairs each season.
You might be able to find the leak by looking for oil stains along the line set and connections to the evaporator coils, TXV and compressor. You won't be able to fix it yourself but, can narrow down the window of "time and material" leak trace/repair (it adds up fast $$$).

 

[Flyover]

@WyrTwister: I don't think I can DIY the work. I wouldn't be surprised if it was installed poorly (apparently most of the houses on my block were built fast, the development company ran out of money halfway or something and had to cut corners, etc.), but there's a chance it was installed well because my house and a few others are quite different from the rest. But my house was a rental for a few years too so it took some abuse.

@kok328: Does that line usually run straight from the furnace out of the house to the coils?

 

[user 4883]

@WyrTwister: I don't think I can DIY the work. I wouldn't be surprised if it was installed poorly (apparently most of the houses on my block were built fast, the development company ran out of money halfway or something and had to cut corners, etc.), but there's a chance it was installed well because my house and a few others are quite different from the rest. But my house was a rental for a few years too so it took some abuse.

@kok328: Does that line usually run straight from the furnace out of the house to the coils?

Usually, the most direct/shortest route possible.