How Do I Know If My AC Unit is Dying?

By Vernon Trollinger, September 18, 2017, Energy Efficiency, Green, Home Improvement, Save Money

Welcome to the How Do I Do This? series from Bounce Energy. Each month, we’ll dive into what it what you need to know to shop-for, install, or repair those things in your home to keep your life affordable and convenient. Plus, you’ll (hopefully) learn some useful tips for other projects along the way.

How Do I Know If My AC Unit is Dying?

Let’s face it, HVAC systems are expensive necessities. When yours starts acting up, the thought of having to spend thousands of dollars to replace it can turn a homeowner’s hair white and their spine into jelly.

To spare you from the stress of the unknown, we’re going to go through a series of HVAC “What if’s” so you’ll have a better idea of when it’s time to pull out a screwdriver to fix your existing system or when it’s time to get a replacement.

Let’s begin by assuming that your AC has been running fine and that all of a sudden it’s not. Start with this basic troubleshooting routine.

  • Double check your thermostat settings to be sure that it is set to run.
  • Check the fuse box and look for any tripped circuit breakers. Sometimes voltage spikes can cause them to trip. In most instances, there will be one breaker for the inside unit that controls the blower and another breaker for the outside condenser unit. If you find your AC system breakers have tripped, go to your thermostat and turn the system off.
  • Next, turn on the breakers. Return to your thermostat and turn on the blower fan ONLY. If it runs normally, then it’s a good sign the problem might be elsewhere.
  • Turn the system to cool and go to where you can observe the outside condenser unit. If the fan spins up normally, and the system begins functioning normally, then everything should be ok.
  • If at any time one of the breakers trips again, then there’s a fault somewhere in that circuit and you should seriously consider having a trained professional look it over.

What If’s

The system is running but there’s little or no air blowing, or the blower makes a higher than normal whine.

Location of typical blower motor and wiring harness.

  • Check the air filter to see if it’s completely clogged with dirt. If it is, replace it.
  • Check the return vents to make sure none of them are blocked off by furniture or carpets. Air needs to flow freely into these.
  • Check the evaporator coils. The evaporator coils are where the refrigerant from the outside condenser cools the air from the blower. These coils can collect lots of fine dust over the years and once in a while they need to be cleaned off. Turn off the system and remove the access panel. The evaporator coils are in an A-frame. BE VERY CAREFUL not to bend or damage the coils or the any of the connections. Gently use a dust wand vacuum attachment to remove the dust. Gently wipe off any stubborn clogs of dust with a cloth and mild spray cleaner. For stubborn grime, you can get foaming AC evaporator coil cleaner. Lastly, replace access the panel.
  • Check the blower. Is the blower motor running? Usually, you can hear it running when you’re standing right next to it without opening any access panels. If the blower isn’t running, turn the the system off and check for loose wiring connections leading to the motor. Vibration from the motor can sometimes shake connections loose.

The blower motor squeaks or squeals a LOT in operation. It also smells hot.

The lack of dust on this blower fan shows the air filter is working well.

  • Try to turn the motor’s shaft by hand. Be sure to turn off the AC system before removing any access panels.  If it’s hard to turn, then the bearings need to oiled. Blower motor bearings are surrounded by felt pads soaked in machine oil which, after 5 or 6 years of continual use, can dry out. The oil ports for the bearings are located at either end of the motor shaft. It can be a messy and time-consuming job but it’s cheaper than buying a new motor. You’ll also want to take a little extra time to clean all the dust and fuzz that falls out from the blower fan.
  • Check the blower fan belt. Because some blower systems are belt-driven, the belts can wear out or stretch over time and need to be replaced.
    Again, turn off the AC system before removing any access panels.

The system is running and the blower is working. But the air’s not cold.

  • Is the outside condenser unit running? If not, check the fuse box to make sure that breaker hasn’t tripped. The outside condenser works best if air can flow freely all around it. If the unit can’t move air through it, it will pull more current trying to cool itself until it overheats and trips the breaker.
  • First, remove any leaves, brush, or vines from around it that might hinder air circulation.
  • Clean the condenser coil fins. The condenser fan blows air around the coils to cool them but dirt and dust clogging the cooling fins can ruin air flow. Every so often throughout summer, wash out the cooling coils with a hose. Be sure to turn off the air conditioning beforehand.
  • Look through the fan grate into the condenser. Keep an eye out for frayed or loose wires since this could lead to dangerous electrical shorts and fires. Frayed wiring can be a sign of gnawing rodents or other pests that might nest inside (for that reason, never cover the unit in winter). Turn off the system and remove any branches or debris have fallen inside. Damaged wiring should be repaired by a trained professional.
  • The fan should spin freely. With the system shut down, use a pencil or long screwdriver to nudge one of the fan blades. If the blades don’t move freely, there may be something wrong with the motor and it might need to be replaced. Again, call in a professional.

The outside condenser unit buzzes noisily. The fan turns slowly or not at all.

Top right: silver power capacitor. Bottom left: black compressor.

  • This is a sign that the power capacitor may be going bad. A normal capacitor is a cylinder with flat ends. On one end, there’s a pair of wire contacts. Capacitors are similar to batteries in that they store electricity but for short periods. Over time, capacitors can degrade and bulge at the ends or start leaking. That’s when they need to be replaced. Check it out by turning off the power supply or circuit breaker to the condenser. Next, find and remove the access panel. Locate the biggest capacitor and see if it’s bulgy or leaking. DO NOT TOUCH THE WIRE CONNECTIONS OR CONTACTS! These big power capacitors can hold enough of a high voltage charge that is dangerous enough to badly burn or even kill you. Replacement should be done by a qualified, licensed repair technician.

The outside condenser unit buzzes noisily but the fan is spinning. No cold air.

  • This is one indication of a bad compressor, especially if the unit is overgrown and dirty. Another indication is that the fan spins up but there’s a noisy clattering or grinding noise coming from the compressor motor. Again, it’s time to call in a professional.

The system is running, both blower and outside condenser seem to be running fine. No cold air.

  • Coolant has probably leaked from the system. The most common places for leaks are where the coolant circulation tubing connects to the inside heat exchanger or the outside condenser. Usually, it’s the outside condenser. These connections are not soldered like copper plumbing. They are brazed, which is usually done with an acetylene torch. Common causes for leaks come from too much vibration or dogs urinating on a unit with aluminum cooling coils.

Parts & Refrigerant Availability

Since 2010, all new HVAC systems use R-410A refrigerant.

In 2010, production and importation of HCFC-22 (R-22) refrigerant was banned. All HVAC systems manufactured after 2009 had to be made to use the new environmentally friendly refrigerant, R-410A. The problem is that pre-2010 HVAC systems can’t use R-410A due to changes in compressor design and other requirements.

So, if you have an old system, there are two factors that you should bear in mind:

Some major replacement parts for pre-2010 HVAC systems are going to become harder to find and thus will cost more. This is because fewer and fewer pre-2010 systems will remain in service as time goes on so there’s no reason for manufacturers to make parts.

R-22 refrigerant is still available, however, it is no longer being produced in the US and is no longer allowed to be imported. In 2020, only recycled, reclaimed, or previously produced HCFC-22 can be used. Consequently, since the amount of available R-22 will go down, the price will likely increase drastically.

Therefore, if your home’s HVAC system is an older pre-2010 system that uses R-22, you should seriously evaluate the pros and cons of repairing it if you are faced with a major repair, such as leaking refrigerant, burned out motors or compressors, or replacing coils. Putting in a newer system sooner rather than later may wind up saving you more money as your older system ages more and R-22 system repair costs keep increasing. In addition, a new energy efficient HVAC system could save you save 20% to 40% of your cooling energy costs.

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About 

A native of Wyomissing Hills, PA, Vernon Trollinger studied writing and film at the University of Iowa, later earning his MA in writing there as well. Following a decade of digging in CRM archaeology, he now writes about green energy technology, home energy efficiency, DIY projects, the natural gas industry, and the electrical grid.

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