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Rheem Air Conditioner Troubleshooting and Repairs

At Fire & Ice, we are a proud Rheem dealer and want homeowners to be equipped with information on troubleshooting and repairing their Rheem air conditioners.

Rheem Air Conditioner Troubleshooting and Repairs

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Fire & Ice Team


May 22nd, 2023

If you’re reading this, it might be because you’re noticing that your air conditioner isn’t running as it should. It might be running too long, making odd noises, or worse, not running at all. What should you do next, especially on a hot summer day when you need relief?

During the busy summer HVAC season, you might reach out to a technician only to discover that you’ll have to wait a few days or more for a service call. While waiting for that appointment, you can pull out the fans from the closet, crank up the portable air conditioners, and dress in loose clothing, but that warm house is miserable.

Your Rheem air conditioner is built to last 10-15 years, but that doesn’t mean it won’t have a problem or two along the way.

In this article, we’ll look at some of the things that can go wrong with an air conditioner, and how a homeowner can prevent a few of them, and maybe fix an issue or two.

Air Conditioner Not Turning On

You know how when you call a computer company and tell them that your unit isn’t functioning, and they first say, “Is it on?” This is like that advice. Make sure both the indoor and outdoor unit power switches are turned on.

This may seem obvious, but occasionally switches get flipped inadvertently. If there’s still no power, check the circuit breaker. If it’s flipped, and won’t stay on when the unit is running, there is probably something wrong that only an HVAC technician or an electrician can fix.

Make sure the thermostat has fresh batteries and that the settings have not been changed. If the setting and the ambient room temperature don’t match, the thermostat may be malfunctioning.

Air Conditioner Not Responding to Thermostat Settings

If your thermostat takes batteries, change them. If it’s connected to your electrical system, check your electrical box to ensure you haven’t tripped a circuit breaker. If it’s been tripped, reset it.

If these tips don’t help, call an HVAC professional. There may be an issue with the wiring between your thermostat and the rest of your HVAC system. If you’ve reset the breaker and it trips again, it’s time to call either an HVAC professional or an electrician.

We’ve also had situations when the homeowner forgot to switch the thermostat from “heat” to “cool.” That’s worth double-checking.

No Cool Air Coming from Supply Registers

If the airflow coming from the supply registers is weak or even non-existent, your ductwork might be clogged. Remove your registers and look in with a flashlight to check your ducts. If you see visible blockages, remove them.

If the ducts have never been cleaned, they could be full of dust. This is rare, but we have seen ducts into which drywall contractors shoved debris. That would affect airflow.

You might consider hiring a duct-cleaning company to give your ductwork a full examination.

Check the Air Filter

A dirty air filter can turn into a clogged filter, and that will block air. As a result, your blower fan in the furnace will have to work extra hard to move air throughout your ductwork. This can create many problems.

What you’ll notice in the short term is a reduced airflow coming from the supply registers. 

We’ve “repaired” systems where the only thing wrong was a hopelessly clogged filter.

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A clean filter restores airflow, allows the system to work more efficiently, creates better indoor air quality, and restores airflow to the entire ductwork.

Rheem Air Conditioner Error Codes

This Rheem air conditioner repair guide will explain common issues, provide troubleshooting tips, and show you how to decipher error codes.

CODE: Error Code 0

PROBLEM: Unit is on standby and operating normally.

FIX: Normal operation.


CODE: Error Code C

PROBLEM: Unit is operating normally and in a cooling stage.

FIX: Normal operation.


CODE: Error Code Flashing C

PROBLEM: Cooling was commanded during an active anti-short cycle.

FIX: Wait until unit timer has expired or press the TEST button to defeat short cycle delay.


CODE: Error Code D1

PROBLEM: No shared data.

FIX: Replace memory card with correct system information.


CODE: Error Code D3

PROBLEM: Airflow mismatch.

FIX: Replace with properly sized air handler.


CODE: Error Code D4

PROBLEM: Memory card in control board is invalid.

FIX: Check if memory card is present and ensure it matches device.


CODE: Error Code D8

PROBLEM: Old shared data system data is obsolete.

FIX: If system will not operate, order new memory card to update system information.


CODE: Error Code T

PROBLEM: Unit is in test mode.


CODE: Error Code P

PROBLEM: There’s no current going to the compressor.

FIX: Check to see if the motor protector is open or line voltage is disconnected.


CODE: Error Code 1

PROBLEM: The compressor is running continuously.

FIX: Check to see if there is low refrigerant, air duct leakage, a dirty outdoor coil, or a dirty air filter.


CODE: Error Codes 02, 29, and flashing L29

PROBLEM: High-pressure problem.

FIX: Check if there is a dirty outdoor coil, outdoor fan is not running, liquid line restriction, or excessive refrigerant charge.


CODE: Error Code 03

PROBLEM: Unit is short-cycling.

FIX: Check thermostat wire connections (R. C. 1. & 2) and thermostat location (too close to discharge grill). It also might be a case that your unit is oversized.


CODE: Error Codes 05, 06, 07, L6, and L7

PROBLEM: Problem with the compressor because of an open circuit.

FIX: Check for damaged, miswired. or wrong run capacitor, broken wires, loose connectors, or miswired compressor, compressor windings for continuity, and open compressor internal protector.


CODE: Error Codes L4

PROBLEM: The rotor is locked.

FIX: Check if there is a bad run capacitor, low line voltage, excessive refrigerant in compressor, or seized bearings in compressor.


CODE: Error Code 09

PROBLEM: Secondary voltage is low.

FIX: Check if the control transformer is overloaded or for low line voltage.


CODE: Error Codes 21 and flashing L21

PROBLEM: Low-pressure control is open.

FIX: Check if unit has low refrigerant charge, indoor coil is frozen, dirty indoor coil or filter, indoor blower is not running, or expansion valve is not operating correctly.


CODE: Error Code 27

PROBLEM: Low or no line voltage.

FIX: Check incoming line voltage to the disconnect and unit and wiring connections.


CODE: Error Code 28

PROBLEM: High line voltage fault.

FIX: Check line voltage.


CODE: Error Code 30

PROBLEM: On-board fuse is open.

FIX: Check if low voltage wiring at R and C is damaged or miswired.


CODE: Error Code 80

PROBLEM: Unit isn’t meeting minimum airflow requirements.

FIX: Replace with properly sized unit.


CODE: Error Code 83

PROBLEM: Problem with the condenser coil temperature.

FIX: Check sensor is installed correctly on control and replace the sensor.


CODE: Error Code 84

PROBLEM: Problem with the outdoor ambient temperature fault.

FIX: Check unit placement. If the outdoor unit is in a high temperature area, wait until the ambient temperature drops and check sensor reading. Check sensor is installed correctly on control. Replace the sensor.


CODE: Error Code 93

PROBLEM: There’s a problem with the internal control.

FIX: Check control for proper system operation. Replace control.

Rheem Air Conditioner

Why Is Your Rheem Air Conditioner Struggling to Cool Your House?

Maybe your machine is perfect, but you’re still uncomfortable. The worst days of summer can test anyone’s patience. When you turn to your trusty air conditioner for relief, it would be nice if it could cool you off as much as you desire.

It’s not always that simple.

When it’s 90 or higher - and let’s not even consider how high humidity can make it feel on top of that - your AC has limits no matter its age, how well it was installed, its manufacturer, etc.

As a rule of thumb, when it’s 95 out, your AC can cool your house to approximately 70-80. Your air conditioner will be able to cool to about 15-25 degrees below the outside temperature.

If it’s 95 degrees outside, and you set your thermostat at 65 degrees, there’s almost no chance your system will get the indoors to 65 degrees.

A Larger, More Powerful AC May Not Be a Solution

If you’re feeling warm in the house though the AC is running a lot, you might consider a new unit that might be a bigger size. That may or may not be the answer.

If your air conditioner is too big, it does something called short cycling. It will turn on, meet the thermostat’s temperature setting, then shut off. But it might not run long enough for the fan to truly condition the air. The air needs a chance to mix to avoid hot and cool spots. For full conditioning to take place, the unit needs to circulate the air so that warm, humid air has a chance to travel through the return air ducts.

A bigger-than-recommended system will cool your home too quickly, and will leave you with a cold jungle: cool air, high humidity.

It will also lead to a shorter life expectancy for your AC due to its constant on/off operation.

The proper way to size a new unit is through a Manual J Load Calculation. It should be a requirement for salespeople, but it’s often skipped because it takes time. It takes about 15 minutes to do one. So consider this: If a potential HVAC partner skips this easy, quick step, how many more corners will they cut during the installation process?

Leaky Ductwork Can Diminish Airflow

In a typical house, about 20 to 30 percent of the air that moves through the duct system is lost due to leaks, holes, and poorly connected ducts.

Because ductwork is often concealed in walls, ceilings, attics, and basements, repairing them is not always easy.

If you feel like sealing the gaps and cracks yourself, you can use mastic sealant or metal tape on the ducts that you can reach. Despite its name, don’t use duct tape; it doesn’t last very long.

You can also check the duct connections at vents and registers.

Check for a Refrigerant Leak

You would be amazed at how many houses we visit that have a leak in the refrigerant line. If your system is low on refrigerant, it won’t be able to cool your home properly.

If an air conditioning system has lost refrigerant through a leak, the lost amount of refrigerant needs to be replaced (which is known as recharging). Depending on how much coolant was lost, this can be pricey because if you have an old unit, the refrigerant is probably R-410A. It’s not being manufactured anymore, so supplies are scarce.

If your system continually leaks refrigerant, it may be due to corrosion or normal wear and tear. In this case, you'd likely have to replace parts, or you might have to consider an air conditioner replacement depending on its age.

An HVAC technician in a hurry might try to tell you that the AC needs recharging but doesn’t mention the leak. This is OK if you’re going to buy a new air conditioner soon, as the performance issues from the leak won’t affect you for very long. But if you plan on keeping your unit for a few more years, the refrigerant will continue to leak, leading to another service call and more recharging when your air conditioner is blowing warm air.

Read more: Sloppy AC Repair in Columbus, Ohio: What to Watch Out For

Rheem air conditioner

Repair or Replace an Aging System?

If your air conditioner is 10 years old or older, it might be time to invest in a new unit.

We get asked all of the time how long an aged AC will last. The truth is that we have no idea. It could last a day, a month, a year, or five years.

Only you can make the call about when to make a change. One big factor to consider (besides the age of your unit) is the amount and number of repair bills. Some won’t cost much and will be worth it. Other AC repairs - such as replacing the evaporator coil or compressor - run into thousands of dollars.

Read more: Should I Repair or Replace My Air Conditioner?

Keeping the old unit until it breaks down may save you on replacement costs, but it’s costing you in other ways. Old machines simply aren’t as energy-efficient as new ones. Your energy bill will reflect how much harder it has to work to cool things off. You’ll get less and less comfort from it in terms of both temperature and humidity control.

Read more: Cost of an Air Conditioner: Replacing Your AC Unit

Dirty Condenser Coil

If your air conditioner is running, but not lowering temperatures inside, one issue could be a blocked or clogged condenser coil.

The condenser coil removes the heat from the refrigerant; the fan pulls air across the condenser coil so that it condenses into a liquid. When operating correctly, the condenser fan draws air into the outdoor unit through the condenser coil to pull heat energy out of your home.

The dirtier the coil gets, the harder your air conditioner has to work. The efficiency decreases, which means that you’re paying more to stay comfortable. This is a common occurrence.

The coil can get dirty from grass clippings, cottonwood, and dead leaves. This is a case where you can perform some DIY magic, with a word of caution. Don’t spray from the outside in; that pushes the crud toward the coil, and it won’t breathe any better.

Also, don’t use a pressure washer. That’s too strong, and you could damage the coil

The proper way to clean a condenser coil is to remove the top of the AC and spray the unit from the inside out. That forces the dirt out. If you’re not comfortable taking this step, an experienced tech will do it for you.

Rheem’s Warranty Coverage

New Rheem air conditioners are protected by a warranty that could save you hundreds or thousands of dollars on repair costs. The warranty terms depend on the model of your cooling system.

Air conditioners in Rheem’s prestige series come with a 10-year limited parts warranty. Models from their Classic series come with a 5-year limited parts warranty, as well as a 10-year conditional parts warranty. To be eligible for the limited warranty, certain conditions must be met regarding registration, installation, and ownership.

Register and access your Rheem AC warranty by clicking here

Diagnosing Rheem Air Conditioner Problems in Central Ohio

 Tasks such as changing your filter when needed and scheduling routine maintenance are good practices for any system. In addition, we recommend that your air conditioner get a tune-up once a year - in the spring would be best, before the heat of summer begins.

If you’re dealing with a Rheem that’s not producing enough air or not turning on, it’s time to schedule a visit from a technician.

At Fire & Ice, we take pride in doing the work correctly the first time, every time. Whether it’s air conditioning repair, replacement, or cleaning, we have the expertise and knowledge to get your system working to provide maximum comfort to your home. If you’re in Columbus or elsewhere in Central Ohio, reach out to us today.

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