AC by J’s Guide to Understanding AC & Heating

Are you in the market for a new heating or cooling system? If so, you’re likely doing your research. An HVAC system is a large investment, and you want to find the right replacement system for your home. No matter where you are in your search for a new heating or air conditioning system, AC by J can help. This guide offers information regarding the parts in your home’s HVAC systems. Or, you can call us if you have any questions you like answered directly.

This is an air conditioner start device.

Causes of failure:
  • Internal short or open circuit
  • Weak capacity (caused by shorted plates)
  • Leaks or bulged housing
  • A hard starting compressor
  • A short cycling compressor

Did you know? When a run capacitor fails, it is wise to consider a Compressor Hard Start Kit to avoid secondary system failure.
Weak Capacitor Chart:

Replace a capacitor, not within the following range:
  • 60UF 63.8/58.4
  • 55UF 58.3/51.7
  • 45UF 47.7/42.3
  • 35UF 37.1132.9
  • 30UF 31.8/28.2
  • 20UF 21.2/18.8
  • 15UF 15.9/14.1
  • 10UF 10.6/9.40
  • 7.5UF 7.9517.05
  • 5UF 5.3/4.70
  • 3UF 3.18/2.82

This is the main switch that supplies power to your compressor.

Causes of failure:
  • Pitted or corroded contact points
  • Short cycling
  • Insect(s) shorted out contact points
  • Contacts stuck open or closed
  • Burned wiring
  • Burned out or shorted coil

Did you know? The major killer of compressors is a contactor with pitted or corroded contact points.

The compressor hard start kit reduces starting AMPS.

Causes of failure:
  • Relay contact stuck or burnt
  • Compressor drawing extreme amps at startup
  • Voltage drop (bad contractor points)

Did you know? Reducing amps at startup will prolong the life of your system.

These help to circulate the household air.
Dirty Blower

Causes of failure:
  • Shorted or open motor windings
  • Seized motor bearings
  • System age
  • Out of balance or broken fan blade
  • Short cycling
  • Defective capacitor

Did you know? If the condenser fan/blower has failed and the unit is 8 to 10 years old or older, you should consider system replacement. Ask the experts: Condenser fan/blower failure is a good indication that the air conditioner is old and more trouble is on the way. A complete system replacement is highly recommended.
Clean Blower

Causes of failure:
  • Motor electrical failure
  • Worn or seized motor bearings
  • Noisy blower
  • Blower running below normal speed
  • Wheel defective or out of balance
  • The dirty blower motor or wheel

Did you know? Quality contractors will replace both the blower wheel and the blower motor when the blower motor needs replacing. This can limit annoying blower noise and prevent premature failure of the replacement motor bearings. Ask the experts: Often the blower wheel is severely damaged when trying to remove it from a rusted motor shaft.

Having a dirty condenser coil prevents efficient heat transfer.

Dirty Condenser Coil:
  • Air conditioners or heat pump condenser coils can get plugged up by dust, dirt, pollen, grass, and other foreign debris.
Problems caused by this condition:
  • The unit loses the ability to remove heat from the system
  • Results in higher pressures in the condenser which causes the compressor to pull amps
  • Higher amp draw means higher electric bills
  • Lack of airflow through the condenser causes the condenser fan motor to run hotter than normal and the compressor to run hotter because of the higher load conditions
  • Premature failure of compressor and/or condenser fan motor
  • Higher than normal electric bills.

As a member of our Comfort Club, our team will clean your system’s condenser coils every visit to ensure maximum efficiency.

A dirty filter reduces efficiency and shortens system life.

Dirty Filter or Evaporator Coil:
  • Dirty filters or evaporator coils cause the air side of the equipment (the part that delivers conditioned air in the dwelling) to lose the ability to deliver the proper amount of air inside the home
  • Diminished airflow capacity causes the evaporator coil to starve for air. All evaporator coils are designed for a specific volume of air passing over them. If the specific volume of air is not attained through normal operation there is not enough heat transfer from the air to the coil. This can leave some of the refrigerants in a liquid state
  • Problems with not evaporating all of the refrigerants in the coil are that the liquid refrigerant can be harmful to a compressor
  • The liquid doesn’t compress so the compressor, which is designed to compress, may fail mechanically if liquid makes it’s way to the compressor
  • The fan for the Blower will run at higher than normal temperatures and that leads to premature failure

Did you know? Other things that can result in diminished airflow are collapsed ductwork, bad blower motor, and low refrigerant charge. This will cause the evaporator coil and suction line to freeze.

A transformer supplies low voltage to heating and cooling control circuits.

Causes of failure:
  • Control shorted in system
  • Low volt wiring shorted or grounded
  • Unit over-taxed by controls
  • Transformer coil shorted
  • Improper primary voltage
  • Power spike or lightning strike

Did you know? When a transformer fails, it is almost always an indication of further system failure.

The compressor is the heart of your system
Heat pumps & AC units move heat by circulating refrigerant through indoor and outdoor coils at different pressures.

Changing a shorted or “burned out” compressor involves:
  • Removing the refrigerant
  • Cutting out the bad compressor
  • Welding in a new compressor
  • Changing any drier & using an “HH” type drier
  • Cleaning the line of debris, using a high-performance vacuum pump to remove any air or moisture
  • A micron gauge is used to determine the level of deep vacuum
  • Weighing in the manufactures recommended amount of new refrigerant
Causes of failure:
  • Inaccurate refrigerant charge
  • Dirty coils/lack of airflow
  • Improper installation techniques
  • Lack of proper maintenance
  • Power fluctuations/improper voltage

Ask the experts: Anytime a compressor fails, it is a good idea to consider a new system. See tips for buying a new air conditioner

This is a device that regulates the flow of refrigerant into the heat absorbing coil.

Causes of failure:
  • Loss of bulb charge
  • Debris clogging the valve
  • Age seizing moving parts
Did you know?
  • A bad TXV could be a sign of a failing compressor
  • To change a TXV requires all the steps needed when changing a compressor

Your thermostat controls your heating and cooling systems and allows the indoor fan to run continuously or intermittently.

Causes of failure:
  • Worn thermostat or sub-base
  • Low voltage wiring shorted or grounded
  • Defective heating or cooling controls
  • Electrical or mechanical failure
  • Power spike or lightning strike

Did you know? When a thermostat fails, it can be an indication of further system problems.

This is designed to prevent costly water damage.
The EZ Trap safety switch is designed to prevent costly water damage by shutting off your system any time the condensate drain line becomes plugged or blocked. The clear p-trap and brush are designed to allow us to see any blockage and allow access to clean out the trap easily. For more information visit
Did you know? The EZ Trap will prevent costly drywall damage and prevent excess moisture that can be a source of mold and other unhealthy conditions in your home.

This is the most advanced low-level carbon monoxide monitor available

Features of this unit:
  • An advanced electromechanical sensor designed to accurately measure low levels of carbon monoxide (CO) providing an early warning of toxic CO levels in your home
  • Detects CO continuously
  • Resistant to false alarms caused by normal household contaminants
  • Digital readout of CO in parts per million (PPM)
  • A continuous circling line on display when the reading is below S PPM
  • 2 years limited warranty
Did you know?
  • Carbon monoxide kills thousands of people each year and injures many more
  • Like oxygen, CO enters the body through the lungs during the normal breathing process
  • It competes with oxygen by replacing it in the red blood cells
  • Reduces oxygen to the heart, brain, and other vital organs
  • In high concentrations, CO can kill in minutes

For more information on CO, visit
Ask the experts: Low-level exposure (less than 35 PPM) to CO can be confused with flu-like symptoms, food poisoning, or other illnesses and can have significant long term health risks if left untreated.

This is a tool that measures air pressure in the duct

Did you know?
  • All HVAC systems are designed to work at or below 1″ water column (a measurement of pressure)
  • If your static pressure is too high your AIC unit may fail prematurely
  • High static pressure also makes your unit work harder, resulting in higher than normal utility bills.

Ask the experts: The most common cure for high static is adding a return duct to allow your system to breathe.

The combustion analyzer is a test used to determine proper combustion in gas appliances.

Did you know?
  • 90% of gas furnaces have never had a certified combustion test completed
  • Without a combustion analyzer test, your system may be producing excess carbon monoxide and wasting energy
  • Comfort Club members receive an annual combustion test included in your membership

This is a tool used to test motor windings.

Did you know?
  • A motor or compressor that tests in the caution range is a sign of potential failure
  • If you can catch a compressor with weak winding you should change it before it has a “burn out” to prevent contamination of your system

Ask the experts: Any time a compressor fails it is wise to consider a new high efficient system.

FAQs: What You Need to Know

How does my AC system work?

Air conditioning systems move warm air from inside your home over an evaporator coil, which contains a liquid refrigerant. As the refrigerant absorbs heat from the air, it warms up and evaporates (while remaining inside the coil). The now-cool air is blown back into your home, typically through ductwork. The refrigerant, now a warm gas, travels to the condenser, which is located in a unit outside your home. The condenser extracts heat from the refrigerant and releases it to the outside air; meanwhile, the refrigerant cools and returns to liquid form. It’s then circulated back to the evaporator coil, where it starts the process again. This cycle repeats throughout the day so your AC system can provide cool, refreshing conditioned air.

What are the common causes of AC system failures?

The top three causes for AC system failures are electrical issues, such as weak connections or bad circuits, motor failures, and a buildup of dirt that restricts airflow.

Why does my AC system smell?

That foul smell coming from your AC system might be from a number of things. If you are smelling damp, mildewy aromas coming from your AC, it may be due to excess moisture in the system from a clogged filter. If you are smelling a burnt smell, your system may have bad electrical contact points in the compressor that will need replacing right away.

How do I clean my AC system?

Make sure that your filter, condenser coil, and blower are free of dirt or dust buildup. This way, air can continue to flow freely through the system.
Does your system need service? At AC by J, we are a full-service plumbing and HVAC experts you can count on for your Phoenix and Scottsdale, AZ area home. Call us today or contact us online!

Choose AC by J for Air Conditioning, Heating & Plumbing in Phoenix, AZ

We offer the fastest, most reliable service on all makes and models of AC and heating equipment in the Phoenix area. Our technicians obtain ongoing training and hold the highest industry certifications possible, so you will receive dependable and efficient service with every visit. No matter the time of day, customers throughout the Arizona area have come to depend on us for all their plumbing, air conditioning, and heating needs. As a local, full-service plumbing, and HVAC company, we are ready to help solve any home comfort problem you have.

We are proud to offer:
  • 3-Hour Response Time Guarantee
  • 24/7 Emergency Service on All Makes and Models
  • New System Installation
  • Emergency Repair
  • A Satisfaction Guarantee
  • Complete Staff of Professional Master Certified Technicians
company icon
Schedule an appointment for heating, air conditioning, or plumbing services in Phoenix and the surrounding areas.