Why is my Air Conditioner Blowing on and off?

If your air conditioner is turning on and off for a short time then on after a short time, you're not alone. This is one of the most frequent complaints that homeowners have throughout the cooling season.

With real service calls, a homeowner will first think their HVAC system is functioning as normal because cold air is still blowing from the vents. One of the first indicators that something is not working as it should within the system, however, is “short cycling,” or frequent turning on and off of the system. This is why homeowners often seek out the services of air conditioning professionals in Belton, TX, as early diagnosis can help uncover potential problems before they result in decreased comfort, increased energy bills, or significant system failure.

The significance of this issue is that short cycling usually isn't an inconsequential annoyance. If left unaddressed, it can slowly start to drive up energy bills, decrease comfort, cause equipment wears and tear, and cause costly repairs.

The types of issues HVAC technicians typically encounter in homes that experience short cycling.

The real-life situation of a short cycling situation in a residential cooling system typically does not start with a significant mechanical fault.

Rather, homeowners often have been noticing minor warning signs for weeks or months before calling for service and then finally make that phone call to a technician.

Typical comments include:

• Years later, "The house doesn't feel as cool as it did before.

• The AC turns on regularly every few minutes.

• I’ve noticed my electric bill has increased recently.

• “Some of the rooms are comfortable while others are warm.”

• “System appears to be running around the clock but is never productive.”

Based on field experience, these symptoms are commonly indicators of a restriction in the airflow, thermostat problem, refrigerant leak or progressive electrical faults.

The Difference between Normal Cycling and Short Cycling.

When it is working well, the air conditioner should run during certain periods of the day and then shut down.

The system should:

• Turn on when the temperature inside is greater than the thermostat setting.

• Run long enough to be able to take heat and humidity out of home.

• Turn off when target temp has been achieved.

• Do not use until cooling is required again.

Short cycling is when the system shuts down before a normal cooling cycle is completed and re-starts again and again.

This usually leads to the following in real homes:

• inconsistent indoor temperatures

• higher humidity levels

• reduced comfort

• increased operating costs

This is the most common causes of AC short cycling.

The blockage of air flow due to a dirty filter.

A dirty air filter is one of the most frequent issues that can be identified on an HVAC service visit.

Many homeowners don't realize how much air flow will impact system performance.

If the flow of air decreases:

• cooling efficiency drops

• internal temperatures become unstable

• The system components are subjected to extra stresses

• cooling cycles are reduced in length and increased in number

In reality, even a misadjusted filter can produce the effects that are seen in much more severe system problems.

Thermostat Issues

Thermostat placement or failure is another common cause.

Technicians are frequently called on to locate thermostats in the following ways in the real world:

• near sunny windows

• Over the supply vents

• Close to kitchen or heat producing appliances

These can result in incorrect temperature measurements, and cause the system to start and stop unnecessarily.

Refrigerant Problems

Cooling problems and short cycling are generally caused by low refrigerant levels.

A refrigerant leak is a slow leak that can occur over time, while equipment failure is a sudden failure that can happen anytime.

Homeowners typically notice:

• longer cooling times

• rising utility bills

• weaker cooling performance

• increased system runtime

When you have a comfort issue, the leak may have been present for a long duration by now.

Frozen Evaporator Coils

Another common problem that technicians have to deal with is frozen coils.

They can be the result of:

• restricted airflow

• refrigerant imbalances

• dirty filters

• blower motor problems

It is a surprise to many homeowners to discover that ice can still form on the roof during very hot weather conditions.

Oversized Air Conditioning Systems

One of the common misconceptions is that bigger means better.

In fact, one of the most common contributors to short cycling is actually oversized systems.

The unit cools the thermostat area too quickly and thus turns off before it can cool the whole house.

This can result in:

• uneven temperatures

• poor humidity control

• increased equipment wear

Electrical Component Wear

Other aging electrical components can also cause short cycling, like:

• capacitors

• contactors

• relays

• control boards

These problems are often more apparent from field experience during periods of high summer demand under increased system stress.

How short cycling relates to comfort and operating costs.

While the constant cycling may be a nuisance to some homeowners, it's often more serious than that.

• Higher Energy Bills

• All startups need extra electricity power.

• The repeated cycling during the day reduces system efficiency and increases operating costs.

• Uneven Cooling

In hot weather, the air conditioning system may be using a short cycling, which can cause air to not flow equal throughout the dwelling.

As a result:

• Several rooms are still hot

• others cool quickly

• The overall comfort suddenly drops. The overall comfort level becomes erratic.

• Poor Humidity Control

Air conditioners dehumidify and cool the air.

If cycles are too short, the system could cool the temperature down just a bit but the moisture in the air would not be removed.

The home will feel cool, but not comfortable.

More wear on high dollar parts.

The most stressful time for the compressor is when starting up.

A frequent cycling will cause damage and a higher chance of future maintenance.

While this is a more comprehensive list, it is not exhaustive.

These symptoms often precede big time problems from actual HVAC service:

AC is running for only a few minutes at a time

The cooling performance progressively decreases.

Unexpected rise in utility costs

The air flow is less than before

• humidity builds up inside buildings.
  Humidity increases inside buildings.

• excessive noises upon start up

• rooms have very large temperature differences

Early recognition of these indications can avoid the more costly repairs in the future.

Homeowners can do before they schedule service.

A few simple checks can lead to the discovery of obvious problems.

Homeowners can:

Change soiled air filters

• verify thermostat settings

• keep supply and return vents open

• Clean the outside of the air conditioner unit.

• Inspect for obstructions of air passages

But refrigerant issues, electrical malfunction and compressor problems must be diagnosed professionally.

Preventive maintenance is effective in eliminating many cycling problems.

Regular maintenance can allow HVAC technicians to notice that a pattern of fewer short cycling problems can be seen in systems that receive regular upkeep.

Routine service is used to detect:

• airflow restrictions

• refrigerant loss

• electrical wear

• dirty coils

• thermostat calibration problems

Solving these problems early will cost much less than waiting for one of the major components failing.

Final Thoughts

Short cycling is a phenomenon typically not observed in real residential HVAC applications unless there is a reason behind it. The vast majority of cases result from the gradual onset of restricted air flow, inaccurate thermostats, refrigerant problems, electrical wear or sizing problems.

Fortunately, these issues usually yield red flags early in the crisis, long before it reaches the point of total meltdown. Those who begin to fix those signs at an early stage usually have lower repair costs, greater comfort, higher energy efficiency and extended equipment life.

Knowing the reason an air conditioner continues to turn on and off is not just a nuisance, it is an early sign that the air conditioner needs repair prior to a smaller problem turning into a big repair.