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Rheem AC Not Cooling Properly: Why And How To Fix It?

Rheem AC Not Cooling Properly: Why And How To Fix It?

Experiencing insufficient cooling from your Rheem AC on a scorching summer day can be quite frustrating. If you’re wondering about the reasons behind your Rheem AC’s ineffectiveness, you’re not alone. We consulted experts to help identify the potential problems causing this issue, and here’s what we found.

There are several factors that can lead to your Rheem AC failing to cool adequately:

  1. Blocked air filters
  2. Dirty coils
  3. Damaged compressor
  4. Faulty thermostat
  5. Defective control board

Let’s delve into why your Rheem AC may not be cooling properly and explore how you can diagnose the problem. We’ll also provide a step-by-step guide for resetting a Rheem air conditioner.

Why Isn’t My Rheem Air Conditioner Cooling?

As global temperatures rise and extreme heat events become more frequent, air conditioning has become increasingly crucial.

The impact of high heat goes beyond mere comfort. Extended exposure to extreme heat and high temperatures can lead to severe health conditions, including heat cramps, heatstroke, heat exhaustion, and even death.

While your Rheem AC is reliable in creating a comfortable living and working environment, it may occasionally fail to cool. This inefficiency can be attributed to poor maintenance or wear and tear, resulting in defective parts.

Clogged Air Filters
Air filters trap dust, dirt, and other airborne contaminants, ensuring cleaner interior components and purifying the cold air released into the room. However, when filters aren’t cleaned or replaced regularly, accumulated dirt obstructs airflow, causing your AC to lose its cooling ability.

Rheem AC Not Cooling Properly: Why And How To Fix It?

Dirty Coils
Rheem air conditioners consist of both evaporator coils and condenser coils. These coils contain a refrigerant that absorbs and releases heat at various stages within the AC system.

In the evaporator coils, the refrigerant absorbs heat from indoor air, transforming into a hot liquid. It then travels from the evaporator coils to the condenser coils through the compressor. Upon reaching the condenser coils, the refrigerant releases the absorbed heat outdoors as a gas.

When the coils become dirty, they fail to efficiently absorb or dissipate heat outdoors. Consequently, your air conditioner won’t cool effectively.

Damaged Compressor
The compressor is responsible for pumping and pressurizing the hot liquid refrigerant, facilitating its movement within the AC system. Increased pressure transforms the coolant into a gas, allowing it to release heat outside when its temperature exceeds outdoor temperatures.

A faulty compressor fails to apply sufficient pressure to the refrigerant, keeping it in a liquid state. It may also struggle to pump the refrigerant to the condenser, where heat is released. As a result, your AC won’t cool properly.

Faulty Thermostat
The thermostat monitors temperature changes and triggers the fan and compressor when temperatures exceed pre-determined levels. If the thermostat is defective, it won’t accurately detect temperature changes, leading to inadequate cooling.

Rheem AC Not Cooling Properly: Why And How To Fix It?

Defective Control Board
The control board regulates voltage to the fan motor and other components. When it malfunctions, certain AC parts may not operate optimally or may stop working altogether. Consequently, your AC fails to cool effectively.

How To Troubleshoot A Rheem Air Conditioner That Isn’t Cooling

Check The Air Filter
To improve air circulation, it’s recommended to change your AC filters regularly. If you suspect dirty filters are the culprit behind your AC’s inadequate cooling, check if the back of your AC unit feels excessively hot. You may also notice warm air emanating from the appliance’s rear.

Dirty filters can trigger allergy attacks and respiratory infections as they become less effective at trapping dust and pollutants. Inspect the surfaces or furniture near the vents for dust accumulation. Alternatively, hang a white sheet around 5 inches away from an AC vent for one hour. If dust collects on the sheet, your filters are long overdue for replacement.

When changing filters, ensure you select ones that are compatible with your unit. The user manual can guide you in choosing the right fit. If your AC has reusable filters, wash and fully dry them before reinstalling.

Inspect The Coils
The evaporator coils are situated in the AC’s indoor unit, while the condenser coils are located in the outdoor unit. Consult the manufacturer’s guide to locate the coils and check if they’re dirty. Look for frost buildup along the refrigerant line, which indicates dirty coils.

Additionally, observe how long it takes for your home to cool. Dirty coils can cause the unit to run longer cycles in order to achieve the desired cooling level.

Since the coils are delicate, it’s advisable to schedule maintenance and have an HVAC technician clean them to avoid causing costly damage to your AC. Regular coil cleaning during annual maintenance ensures they remain in good working condition, maximizes AC efficiency, and keeps energy bills within reasonable limits.

Check The Compressor
Compressor failure can occur due to lubrication loss. Refrigerant and oil circulate together, and if there’s a leak in the AC system, both substances can escape. When the oil leaks, increased friction between compressor parts can eventually lead to its malfunction.

Blockages in the AC system, such as a clogged expansion valve or orifice tube, can also prevent the compressor from receiving sufficient oil. Without proper lubrication, the compressor may run dry and seize.

Listen for metallic or bearing noises when your AC is running, as these may indicate an impending compressor failure. If the compressor is excessively noisy or doesn’t operate optimally, it may need to be replaced.

You can also use dye or an electronic leak detector to test for oil and refrigerant leaks. It’s crucial to repair leaks promptly to prevent irreparable damage. If leaks are not addressed, you may eventually need to ask a licensed technician to replace the compressor.

Before replacing the compressor, rule out other potential causes for your AC’s inadequate cooling, such as low refrigerant charge, overloaded protector, or a faulty compressor capacitor.

Inspect The Thermostat
A faulty thermostat may display unresponsive buttons or fail to initiate the HVAC system when adjusting temperature settings. It may also cause frequent cycling or failure to stop when comfortable temperatures are reached.

If you suspect a defective thermostat, don’t worry, as replacing it is more affordable than purchasing a new HVAC system. When buying a new thermostat, ensure compatibility with your HVAC system. Remember that thermostats are not one-size-fits-all.

Take advantage of thermostat shopping by upgrading to a model that offers both comfort and control.

Call an HVAC Expert
Some tasks, such as diagnosing the control board, are best left to certified technicians, as misdiagnoses are common. Scheduling a meeting with a professional will ensure efficient restoration of your air conditioner’s functionality in a short period.

Rheem AC Not Cooling Properly: Why And How To Fix It?

How To Reset A Rheem Air Conditioner After A Power Loss

After a power outage, your Rheem air conditioner may not turn on immediately. This is because the AC has protective mechanisms in place to prevent damage from power surges.

The pressure switch in a Rheem AC shuts off the compressor when the refrigerant pressure becomes excessively high. Follow these steps to reset the unit:

Step-By-Step Guide:

  1. Increase the thermostat temperature settings to 80 °F to prevent the unit from turning on while you reset the compressor.
  2. Locate the reset button near the copper lines at the bottom of the case. Consult the user manual for guidance.
  3. Press the reset button once using your finger.
  4. Set the thermostat to your desired temperature.


There are various reasons why your Rheem air conditioner may not be cooling effectively. However, the AC’s failure to cool doesn’t necessarily mean you have to replace it with a new one. This article provides a starting point for identifying potential issues and resolving them.

Scheduling annual maintenance is essential to eliminate common causes of inadequate cooling. If the problem persists, consult a certified professional who can diagnose and repair your unit, restoring its optimal functionality. If all else fails, it may be time to consider replacing the unit.

Rheem AC Not Cooling Properly: Why And How To Fix It?

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Written by HVAC Contributor

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