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This article describes the most common Central Air Conditioner problems that cause central a/c to stop cooling properly, or completely stop running.  Plumbing, Heating & A/C in Plano, Texas provides maintenance & repairs for all brands of Central A/C, Gas & Electric Furnace, and Heat Pumps.  Additionally we sell and install new HVAC Systems from American Standard (same company as Trane), Ameristar (same company as American Standard) and Coleman HVAC (same company as York HVAC).

Al’s also provides full service plumbing maintenance, repairs and replacements for every plumbing component in your home.  Al’s sells and installs Rheem Professional Series gas & electric water heaters, and tankless water heaters.  Al’s is near your home in Plano, TX; Allen, TX; and Frisco, TX.  We service all homes in southern Collin and Denton Counties with no travel charges.

Call Al’s today to discuss any concerns or problems you have with your HVAC System or Plumbing.  We will arrange an appointment at your convenience and offer 24/7 Emergency Service.

Looking For Ways To Reduce Cooling Bills?  We Can Help!

Click Here For 45 Ways To Lower Cooling Costs Without Replacing HVAC:  AlsPlumbing.com 45 Ways To Lower Cooling Costs

 

The Most Common Central Air Conditioner Problems

& The Repairs Needed

two central air conditioner outdoor units

Photo Source: Dreamstime

Central Air Conditioner Problems:  In previous Blog Posts, we have discussed proper maintenance of your HVAC system.  If you are doing that, breakdowns will be notably reduced. However, Central Air Conditioners will stop working due to problems or components that wear out and fail, and not related to maintenance.

There Are Common Central Air Conditioner Problems 

That Most Homeowners Can Check And Correct. 

  • No Power
  • Thermostat Settings
  • Cleaning the A/C drain line
  • Thawing the cooling coil (inside the furnace).
  • Cleaning the outdoor unit.

NOTE: Beyond these 5 items — we don’t recommend nor instruct home owners how to do A/C repairs.   Very high electrical-voltage exists inside a Central A/C System — creating shock or electrocution potential if not correctly handled during repairs.  You can also damage the system if you do something wrong.  HVAC Technicians are trained to; troubleshoot and perform repairs with the correct parts and installation methods.

Not Operational — Due To No Power 

7 Home Owner Correctable Central Air Conditioner Problems.

GAS Furnace System Shut Off Switch Is Turned Off .  This switch getting turned off is one of the common central a/c problems.  This switch shuts down the entire system.   This switch is located on or near a GAS furnace, and must always be turned to on.  NOTE: It’s easy to bump this switch when changing the air filter.  Also, curiosity may temp a child to turn the switch off.

For a gas furnace — this switch will be mounted on the furnace, or within reach of it.  It looks like a regular light switch.  It’s inside a metal box or inset into the wall.

 

Click Below To A System Shut Switch Mounted On A Gas Furnace:  GAS Furnace System Shut Off Switch — on furnace

 

ELECTRIC Furnace Main Shut Off Circuit Breaker (near the furnace) has tripped or is turned off.  An electric furnace has a circuit-breaker on or near the furnace.  This circuit breaker shuts down the entire system.  As with many breakers, it may be tripped but doesn’t appear to be.  Flip the breaker to off, then back on to reset it.

The Main Shut Off for electric furnace will look like a circuit breaker panel switch.   It will be mounted on or within reach of the furnace.

Click Here To See An Electric Furnace System Shut Off Switch: Electric Furnace System Shut Off Switch — Near Furnace

 

Tripped Circuit Breaker (inside the Circuit Breaker Panel).   Flip the breaker to off and back to on.   NOTE: Many beakers trip only partially — and it might look like it’s on.

Click Below To See A Circuit Breaker Switch In: On, Tripped, & Off Position:  

Circuit Breaker In: On & Tripped & Off Positions

Blow Fuse In Outdoor A/C Disconnect Box

IMPORTANT: Turn the HVAC System off (inside the circuit breaker panel) before touching Outdoor A/C Disconnect Box.

Before central air conditioner problems repairs begin — the outside disconnect box is turned off — to protect a/c service technicians from electrocution. When the HVAC System breaker or fuse (inside the home) is not within view — Building Code requires an A/C Disconnect Box be visible from the outdoor A/C unit.  This prevents electrical-hazard if someone turns the breaker inside the home back on.

Additionally, the fuses or switch provide another level of protection for the outside unit.  The fuses / switch are for overload protection. These fuses are sized to the specific load they protect.  They may be a smaller amperage than the circuit breaker’s rating in the circuit-breaker panel.   If a fan or the compressor cannot operate — it will quickly overload, overheat, and burn up.  The fuses / switch in the outdoor a/c disconnect electricity to protect the system.

Blown Fuse In Outside Fuse Box (near the outside a/c unit).  This may be the problem in homes with fuses in the outdoor A/C disconnect box.

CLICK HERE To See The Outdoor Central A/C Disconnect:  Central A/C Outdoor Disconnect Box

Many Newer Outdoor A/C Disconnect Boxes Have Circuit Beakers.  

CLICK HERE To See Inside A Circuit-Breaker Outdoor Disconnect Box: 

View Inside A Circuit Breaker Style A/C Outdoor Disconnect Box

 

Thermostat Not Set Correctly  

The thermostat has a switch to tell the system to Cool OR Heat.  A common central a/c problem results from the the thermostat not being set to “Cool”  And / Or the thermostat’s setting isn’t lower than the indoor temperature.

home thermostat

Photo Source: Dreamstime

SHOWN:  The 3-Position Switch Is Located On The Lower Right Corner Of Thermostat Above.  “Cool” will be on one side.  “Off” in the center, & “Heat” on the other side.

Note: There is another switch for the (blower) fan.  It shows “Auto” & “On” settings — leave it set to “Auto” year round.

Clogged Drain line  

One of the most common central a/c problems is a clog in drain line (for removed humidity).  As your a/c runs, it removes humidity from the air.   Over time — it’s common for the A/C drain-line to clog.

If clogged, the drain pan inside the furnace overflows,  and water leaks out of the furnace.  When the drain line is clogged, the water is  discharged somewhere within the house.  If your a/c is in the attic — you’ll end up with a wet ceiling.  If allowed to continue, mold growth and the risk of the ceiling falling is common.

CLICK HERE To See An Air Conditioner With A Clogged Drain Line:  Ceiling fell due to clogged drain line.

 

An easy way to clear a clogged drain line is with a Wet & Dry Vacuum.  Find where the drain line exists the house.   It’s likely near the outside A/C unit.

Slip the vacuum hose onto the drain line and temporarily seal with duct tape (to create a somewhat air-tight seal).  Turn the vacuum on.  You will likely hear the vacuum’s sound change when the clog is removed.  With attic-installed furnaces, this may take up to three minutes because the drain line is quite long.

Click Below For A YouTube Video Explaining How To Clear A/C Drain Line With A Wet/Dry Vacuum:

  Clear A/C Drain Line With Wet/Dry Vacuum.

Note: If using duct tape doesn’t clear the clog — you can purchase the attachment show in the video.

Frozen Cooling (evaporator) Coil

(inside the furnace or in ductwork above furnace — and not visible)

Image Source: YouTube Embedded Video

If your furnace blower motor is running, but no air is coming from the vents — it’s likely the cooling coil is frozen.

To Thaw The Coil:

  • Turn the a/c off at the thermostat by setting the 3-Position System Switch to “OFF:.
  • Set the fan to “on” at the thermostat.
  • This will thaw the frozen coil.  The amount of time needed depends on how much ice is on the coil
  • Once the air-flow from the air ducts is normal — set the fan back to “Auto” — and the System Switch back to “Cool”.

home thermostat

Photo Source: Dreamstime

Most Common Reasons An Indoor Cooling-Coil Freezes:

  • Thermostat set below 70 degrees. 
  • NOTE: Turning the thermostat lower does not make the a/c cool faster.  It only makes the a/c run longer — and cools to an excessively low temperature.  This can cause a properly working a/c to freeze the indoor cooling coil.
  • A dirty air filter has reduced air-flow.  If your cooling coil has frozen and the filter is quite dirty. Change the filter and thaw the coil.

dirty air filter on left. New air filter on right.

Image Source: CanStockPhoto

  • If the filter is clean, and thermostat is set at 70 or higher, and you have a frozen coil — it’s likely the a/c is low on refrigerant
  • Low refrigerant causes the a/c to run too cold — that freezes the coil.  If low on refrigerant, the coil will continue to freeze.  You will need to call for a/c service to recharge the outdoor unit.

The Following Central Air Conditioner Problems

Must Be Repaired By An HVAC Technician

Your furnace blower running, but warm air is coming out the vents.  First, check to see if the outside unit is running (the furnace blower will run even if the outside a/c unit isn’t run).

There Are Several Reasons Why The A/C Outside Unit Isn’t Running:

No power to the outside unit.  We addressed the “no power” issues early in this post.  If you have checked those, and they’re ok — it’s time to call an HVAC Technician to troubleshoot and repair what’s wrong.  There are many things which can fail.

These Are The Most Common Central A/C Breakdowns:

Failed Contactor:  There are 3 Contactors:

  • For the Compressor in the outside unit.
  • For the Fan in the outside unit.
  • For the Furnace’s Blower Fan

Contactors are automatic switches that start HVAC System components running.   Over time, these contactors may fail due to age, or normal wear & tear.  Failed contactors must be replaced before the a/c will un.

Click HERE To See A Central A/C Contactor Switch:  Central A/C Contactor Switch

Failed Capacitor:  A Capacitor is a rechargeable battery that provides an additional boost of electricity to start a motor running. 

Compressor Start Capacitor:

  • Watts required to Start a 3 ton a/c compressor = 4,800
  • Watts required to Keep a 3 ton a/c compressor running (after start up) = 4,350 watts
  • The difference in watts comes from the capacitor.

Click HERE To See A Central A/C Capacitor:  Central A/C Capacitor

Dirty Outdoor Condenser Coil Clogged.   This coil is inside the outdoor unit (with the compressor). During normal operation, the coil gets clogged with dirt & debris due to pulling in large amounts of unfiltered air to cool the condenser coil.   The coil must be cleaned at the beginning of each cooling season for proper operation.

Click Here To See A Very Dirty Condenser Coil (outside unit) — Before And After:  Condenser Coil Cleaning — Before & After

If not overly dirty, cleaning can be done with a garden hose with a/c turned off and power disconnected at the outdoor Disconnect Box.   If the dirt gets bad enough — an HVAC technician will have to clean the coil with a chemical cleaner.  Al’s Plumbing, Heating and Air Conditioning offers an annual A/C Tune Up.  At that time, we will tell you if the condenser coil needs cleaned (an extra charge).

Dirty Indoor Cooling / Evaporator Coil Needs Cleaned.

The indoor cooling / evaporator coil is inside the furnace, or the ductwork just above the furnace.  This coil can’t be seen without removing a panel.   As indoor air passes through this coil, the air is cooled and some humidity is removed.  This coil is wet the entire time the a/c is running.

Even the best furnace filters allow some contaminants through.  Over time, these contaminants get caught in the indoor cooling coil and build up.  A dirty evaporator coil is a perfect environment for mold to grow — with the blower motor sending mold-spores all over your home.

The coil should be checked annually and cleaned if needed.   Sometimes this coil is removed for cleaning.  The refrigerant must be removed first, then added back once the cooling coil is cleaned and reinstalled.

Click Below To See A Very Dirty Indoor Cooling / Evaporator Coil: 

Very Dirty Cooling / Evaporator Coil With Some Black Mold Present

Refrigerant Leak:  If you notice:

  • your a/c is running more than in the past
  • the air coming from the vents is not as cool as in the past
  • your electric bills have increased
  • the home is too warm and the a/c is running non-stoop

Your a/c may have leaked refrigerant and is low.  Without the correct amount of refrigerant, your a/c will run, but can’t cool at its peak ability & efficiency.  This leads to higher cooling costs and potential failure of the outdoor unit — due to it running without enough refrigerant.

Refrigerant leaks can happen at any location where refrigerant flows.  The cost to repair refrigerant leaks in the outdoor unit or indoor cooling coil may not be justified — due to the age & remaining life of the HVAC System.  In DFW, if the outdoor unit is 15 years or older — refrigerant leak repair  can exceed its value, especially if the a/c requires Freon / R-22 refrigerant.   The indoor cooling-coil replacement is notably less expensive.

For newer systems, it often makes sense to repair the existing equipment.  For leaks in refrigerant lines (connecting the outdoor unit to the indoor cooling coil)  — the technician can typically repair the leak and recharge the system with refrigerant.

NOTE:  If your a/c is older & uses R-22 refrigerant (Freon) — recharging it is expensive, and impossible in the future. 

R-22 / Freon refrigerant is no longer being made (it damages the Ozone-Layer).  Remaining supplies of new R-22 are quite expensive, as the only remaining source of additional R-22 is is “reclaimed” (removed from old a/c or refrigerators before they’re disposed of).

Click Here For A Detailed Discussion About Freon In The Minneapolis Star Tribune Newspaper: 

 Why Freon Refrigerant Has Become So Expensive

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Al’s Plumbing, Heating & A/C in Plano, Texas provides maintenance & repairs for all brands of Central A/C, Gas & Electric Furnace, and Heat Pumps.  Additionally we sell and install new HVAC Systems from American Standard (same company as Trane), Ameristar (same company as American Standard) and Coleman HVAC (same company as York HVAC).

Al’s also provides full service plumbing maintenance, repairs and replacements for every plumbing component in your home.  Al’s sells and installs Rheem Professional Series gas & electric water heaters, and tankless water heaters.  Al’s is near your home in Plano, TX; Allen, TX; and Frisco, TX.  We service all homes in southern Collin and Denton Counties with no travel charges.

Call Al’s today to discuss any concerns or problems you have with your HVAC System or Plumbing.  We will arrange an appointment at your convenience and offer 24/7 Emergency Service.