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This article describes how to solve Central AC Problems — that are common and easily fixed.  Al’s Plumbing, Heating & A/C in Plano, Texas provides maintenance & repairs for all brands of; Central A/C, Gas & Electric Furnaces, and Heat Pumps.  Additionally, we sell and install new HVAC Systems from American Standard (same company as Trane), Ameristar (owned by 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 Garland, TX; Richardson TX; and Wylie, 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.

 

Looking For Tips For How To Reduce Cooling Bills?  We Can Help!

Click Below For 45 Ways To Lower Cooling Costs Without Replacing HVAC:

AlsPlumbing.com 45 Ways To Lower Cooling Costs

 

How To Solve Central AC Problems

We’ll tell you how to Fix Many Of Them Yourself.

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 keep your HVAC System maintained annually — breakdowns are much less likely.  Central AC sometimes stops working for several small problems you can handle yourself.  Below, we describe the most common problems, and how to resolve many of them yourself.

The Most Common Central AC Problems

That Many Homeowners Can Check & Correct

central air conditioner outside unit

Image Source: Dreamstime

Shown: Central A/C Outdoor Unit

In This Article, We Describe How To Troubleshoot & Correct These Problems — That Cause The Central AC To Stop Running:

  • No Power
  • HVAC System Shut Off Switch
  • Tripped Circuit Breaker In The Circuit Breaker Panel
  • Blown Fuse or Tripped Breaker In Outdoor Disconnect Box
  • Thermostat Settings
  • Clean the A/C drain line
  • Thaw a frozen indoor cooling (evaporator) coil inside the furnace.
  • Clean the outdoor unit.

NOTE: Beyond these items — we don’t recommend nor instruct homeowners 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.

— A/C NOT RUNNING

How To Solve Central AC Problems — That Caused It To Stop Running

close up photo of gas furnace flames

Image Source: Shutterstock

  • Check the System Shut Off Switch — GAS Furnace.  This switch shuts the entire HVAC System down (including A/C).
  •  It’s common to bump this switch while changing the furnace filter.  Also, curiosity may tempt a child to turn the switch off.
  • This switch is a typical light switch.
  • It’s mounted either on the furnace — or within reach of it.
  • If it’s furnace mounted — the switch will be inside a metal box.
  • Note: There’s another Circuit Breaker for the furnace in the Circuit Breaker Panel — for gas & electric furnace.

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

 

Check the System Shut Off Switch — ELECTRIC Furnace.     This switch shuts the HVAC System down (including A/C).

  • With an electric furnace — this switch looks like a Circuit Breaker — because the furnace’s power runs through it.
  • The System Shut Off Switch will be mounted on, or near the furnace.
  • The breaker may have tripped — but appears to be on.  Flip the breaker to off — then back on to reset it.
  • Note 1: There’s another Circuit Breaker for the A/C in the Circuit Breaker Panel — for gas & electric furnace.
  • Note 2: The breaker in the Circuit Breaker Panel for the Furnace must also be on.  Central A/C can’t operate without the furnace running.
  • NOTE: Circuit Beakers often only partially trip — and may look like they’re on.    Flip the breaker to Off — then back On to reset it.

Click Here To See A Circuit Breaker Panel: Circuit Breaker Panel

Tripped Circuit Breaker — Inside The Circuit Breaker Panel

photo of circuit breaker panel

Image Source: CanStockPhoto

  • If your Circuit Breaker Panel isn’t labeled — look for two breakers that are coupled together with a strip of metal.
  • Coupled breakers serve 240-Volt Circuits.   Single breakers serve 120-Volt lines.
  • 240-Volt Electric Service is for; Central A/C and Electric; Furnace, Range, Oven, or Cooktop, Clothes Dryer, & Water Heater.
  • There may be additional 240-Volt equipment — common ones are swimming pool filters & heaters.
  • Note 1: There’s another Circuit Breaker for the A/C in the Circuit Breaker Panel — for gas & electric furnace.
  • Note 2: The breaker in the Circuit Breaker Panel for the Furnace must also be on.  Central A/C can’t operate without the furnace running.
  • NOTE: Circuit Beakers often only partially trip — and may look like they’re on.    Flip the breaker to Off — then back On to reset it.

Click Here To See A Circuit Breaker Panel: Circuit Breaker Panel

NOTE:  In the photo — you can see two breakers that are coupled together.  Look on the left side of the Panel —  and for the label: “Pool Pump”.

 

Blown Fuse or Tripped Breaker In The Outdoor A/C Disconnect Box

Image Source: Dreamstime

The Outdoor Disconnect Box Is Visible Near The Right Edge Of This Photo

  • Solve Central AC Problems Related To Outdoor AC Disconnect Box.

NOTE: Before turning off the Outdoor A/C Disconnect Box — turn the Central A/C Breakers Off (at the circuit breaker panel).  

Before a central air conditioner is serviced — the Outside Disconnect Box is turned off.   This protects A/C Technicians from electrocution.   Electrical Building Code requires an A/C Disconnect Box must be visible from the outdoor A/C unit.  This prevents electrical-hazard if someone turns the circuit breaker (inside the house) back on.

Additionally, the Outdoor Disconnect Box provides another level of protection for the outside unit.  The fuses/breaker provides overload protection.  The fuse or breaker is sized to the specific electrical load it protects.

If the outdoor A/C unit’s fan or compressor cannot operate — it can quickly overload, overheat, and burn up.  During this time, the outdoor A/C unit typically attempts to draw more electricity than is required to run the outdoor A/C unit.

If the Outdoor Disconnect Box detects excessive electricity demand —  it blows a fuse or trips a circuit breaker (inside the outdoor box).  Note: Most newer Outdoor Disconnect Boxes have circuit breakers instead of fuses.

 

Thermostat Settings  

home thermostat

Photo Source: Dreamstime

SHOWN:  The 3-Position Switch Is Located On The Lower Right Corner Of The 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.

This happens a lot — the thermostat wasn’t set to “Cool”.  The thermostat has a switch to set the system to Cool OR Heat.

  • Solve Central AC Problems Related To Thermostat:
  • The thermostat is not to “Cool”
  • The thermostat’s temperature setting is higher than the indoor temperature.

Image Source: YouTube Embedded Video Link

Click On The White Arrow (in center of the image above) — For A YouTube Video Explaining How To Clear A/C Drain Line With A Wet/Dry Vacuum

Clogged A/C Drain line  

  • Solve Central AC Problems Related To Clogged AC Drain Line

Your A/C removes humidity from the air.  Over time — it’s common for the A/C’s drain-line to clog.   If the drain line is 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 where the furnace is located.  If your a/c is in the attic — you end up with a wet / damaged ceiling.  If allowed to continue, mold growth and the risk of the ceiling falling are common.

This is why “condensate (condensation) pumps” are typically used with attic installations.  These pumps have a sensor to let them know if the line isn’t draining.  Then, the pump shuts the A/C + furnace off — to avoid a wet ceiling.

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 A/C Drain Line — Use A Wet & Dry Vacuum

  • Clear The Drain Line This Way — And Typically There’s No Need To Go Into The Attic.
  • Find where the drain line exits the house — it’s likely near the outside A/C unit.
  • Slip the vacuum hose onto the A/C’s drain line.
  • Wrap the connection with a rag, and squeeze it tight while the vacuum is running.
  • You can also temporarily seal the connection with duct tape (to create a somewhat air-tight seal).
  • Turn the vacuum on.

NOTE:

  • With attic-installations, the A/C drain line is long, and it may take some time before the clog has cleared the entire drain line.
  • You should be able to hear the vacuum’s sound change as the clog has cleared.

Frozen Cooling (evaporator) Coil

  • Solve Central AC Problems Related To Frozen Indoor Cooling (evaporator) Coil:

(This coil is inside the furnace or ductwork — and can’t be seen without removing a panel )

 If Your A/C & Furnace Blower Are Running, But No Air Comes The Vents — It’s Likely The Indoor Cooling (evaporator) Coil Is Frozen.

Image Source: YouTube Embedded Video Link

Click On The White Arrow (in center of the image above) — For A YouTube Video Showing A Frozen Indoor Cooling (evaporator) Coil 

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

  • Solve Central AC Problems Related To Indoor Temperature or Glogged Filter
  • Thermostat set below 70 degrees. 
  • NOTE: Turning the thermostat lower does not make the a/c cool faster.  It only makes it run longer — and cool 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 — which 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.

 

These Central Air Conditioner Problems Must Be Repaired By An HVAC Technician

Your furnace blower is running, and 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). If you have checked the Circuit Breaker Panel and the Outdoor Disconnect Box — it’s time to call for an A/C Technician.

There Are Several Central AC Components That (if they fail)

Will Stop The A/C Outside Unit From Running

Below Are The Most Common Central A/C Component Failures:

Failed Contactor

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 run.

There are 3 Contactors:

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

Click HERE To See A Central A/C Contactor Switch:  Central A/C Contactor Switch (scroll down a little)

Failed Capacitor

A failed capacity is one of the most common reasons a Central A/C outdoor unit stops running.

A Capacitor is a rechargeable battery that provides an additional boost of electricity to start the compressor and fan motor running.   Over time, this battery wears out and must be replaced.

It Takes:

  • 4,800 Watts required to Start a 3-ton a/c compressor running.
  • 4,350 Watts required to Keep a 3-ton a/c compressor running (after startup).
  • At startup — the additional watts come from the capacitor.

Click HERE To See A Central A/C Capacitor:  Central A/C Contactor Switch (scroll down a little)

Outdoor Condenser Coil Is Too Clogged 

central air conditioner outside unit

Image Source: Dreamstime

This coil is inside the outdoor unit (with the compressor).  During normal operation, the coil gets clogged with dirt & debris as a result of pulling in huge amounts of unfiltered air to cool the condenser coil.  If the coil gets too clogged, the outdoor unit cannot cool itself and will likely shut off for its own protection.  For maximum efficiency — at the beginning of each cooling season, this coil must be checked (and cleaned if needed).

Click Here To See A Very Dirty Condenser Coil (outside unit) — Before & After:  Condenser Coil Cleaning — Before & After (scroll down a little — photos in 2nd row, on the left)

NOTE:

  • If not overly dirty, this coil can be cleaned with a garden hose.
  • FIRST — Turn A/C off at both the Circuit Breaker Panel (indoors) + the Power Disconnect Box (outside).
  • If the dirt gets bad enough — an HVAC technician will have to clean the coil with a chemical cleaner.

Al’s Plumbing, Heating & A/C offers an annual A/C Tune-Up.  At that time, we will tell you if the condenser coil needs cleaned (an extra charge).

 

Indoor Cooling / Evaporator Coil Is Too Clogged 

 

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

air conditioner refrigerant and gauges

Image Source: Shutterstock

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

A/C refrigerant doesn’t get used up.  If your a/c is low on refrigerant — it’s due to a leak.  Without the correct amount of refrigerant, your a/c will run — but won’t cool efficiency.  This leads to higher cooling costs and potential failure of the outdoor unit — due to it running with low 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.

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 uses R-22 refrigerant (Freon) — recharging it is expensive, and will be impossible sometime in the future. 

R-22 / Freon refrigerant is no longer being made (because it damaged the Ozone-Layer).  Remaining supplies of new R-22 are quite expensive, as the only remaining source of additional R-22 are “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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This article described how to solve Central AC Problems — that are common and easily fixed.  Al’s Plumbing, Heating & A/C in Plano, Texas provides maintenance & repairs for all brands of; Central A/C, Gas & Electric Furnaces, and Heat Pumps.  Additionally, we sell and install new HVAC Systems from American Standard (same company as Trane), Ameristar (owned by 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.