Rheem AC Not Cooling: Causes, Fixes & Repair Costs
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Rheem air conditioner not cooling: what it means
“Not cooling” is a symptom, not a stored fault code. It means the system is running, or trying to run, without lowering the indoor temperature. Most Rheem single-stage condensers have no diagnostic display, so the cause has to be traced by symptom.
Some two-stage and variable-speed Rheem models report faults as LED flash codes on the outdoor control board or on an EcoNet thermostat. Examples include high or low pressure lockouts and compressor protection trips.
On units with lockout logic, the behavior varies by board:
- Some boards retry automatically after a delay.
- Some hold a hard lockout after repeated pressure trips until power is cycled.
Check the label inside your outdoor unit’s service panel, or the installation manual, for your model’s exact behavior.
This page covers central air conditioners. If you have a heat pump, see the separate heat pump not-cooling page.
Rheem air conditioner not cooling: common causes, ranked by probability
- Dirty air filter or blocked airflow. Restricted airflow drops cooling capacity and can freeze the indoor coil. This is the most common cause and the cheapest fix.
- Thermostat settings or power. Causes include a thermostat set to Heat or Fan only, dead batteries, or a setpoint above room temperature.
- Tripped breaker or outdoor disconnect. The indoor blower runs on a separate circuit, so the house moves air but nothing cools it.
- Failed run capacitor. This is the most common electrical failure on Rheem condensers. The compressor or fan hums but won’t start, or runs and overheats.
- Failed or pitted contactor. The outdoor unit won’t engage even though the thermostat is calling for cooling.
- Frozen evaporator coil. It usually results from low airflow or low refrigerant. Airflow stops and ice may be visible on the refrigerant lines.
- Refrigerant leak. Rheem evaporator coils, like many brands’ coils, have had documented formicary corrosion leaks. On models with pressure switches, a leak may trigger a low-pressure lockout.
- Dirty outdoor condenser coil. It causes high head pressure, poor cooling and possible high-pressure trips on hot days.
- Condensate overflow safety switch tripped. A clogged drain trips a float switch that shuts off cooling.
- Outdoor fan motor failure. The compressor runs but overheats and cycles off on internal overload.
- Compressor failure. This is the least common cause but the most expensive one, and it is usually confirmed only after the items above are ruled out.
How to fix Rheem air conditioner not cooling: safe checks first
- Thermostat: Set it to Cool, with the setpoint at least 3°F below room temperature and the fan on Auto. Replace the batteries if the display is blank or dim.
- Air filter: Pull it out. If it’s gray or clogged, or you can’t see light through it, replace it.
- Breakers: Check the main panel for both the furnace/air handler and the AC (usually a double-pole breaker). Reset a tripped breaker once. If it trips again, stop and call a technician.
- Outdoor disconnect: Make sure the disconnect box next to the condenser hasn’t been pulled or switched off.
- Outdoor unit: Look without touching anything. Is the fan spinning? Clear leaves, grass clippings and debris to about 2 feet around the unit. Gently hose the outside of the fins from the top down, with the power off at the disconnect.
- Frozen coil: If you see ice on the copper line or the indoor unit, set the thermostat to Off and the fan to On until it fully thaws. Don’t chip at the ice.
- Vents and registers: Open supply registers and clear blocked return grilles.
- Condensate line: If the drain pan is full or the line is clogged, clear the end of the line with a wet/dry vac. A cup of white vinegar poured into the access tee can help. This may reset a tripped float switch.
- Panels: Make sure the blower compartment door is fully seated. Many units won’t run with it loose.
- One reset: If your outdoor board shows a lockout, turn the power off at the breaker for 5 minutes, then restore it. Do this one time only. If it locks out again, call a technician.
Do not open the condenser’s electrical panel, touch capacitors (they hold a charge even with power off), or attempt any refrigerant work.
How a technician will diagnose it
A competent tech will typically:
- Confirm the call. They verify 24V at the outdoor contactor coil and confirm the thermostat is calling for cooling.
- Test line voltage at the disconnect and contactor, and inspect the contactor points for pitting.
- Test the run capacitor with a meter in microfarads (µF). They compare the reading against its rating, usually within ±6%.
- Measure amperage on the compressor and fan motor and compare it against the nameplate.
- Attach gauges or digital probes. They check suction and liquid pressures, superheat (fixed-orifice systems) or subcooling (TXV systems, common on Rheem). These are compared to the charging chart on the unit.
- Measure temperature split across the indoor coil. A normal split is roughly 15–20°F.
- Check airflow: static pressure, blower speed and filter, and evaporator coil cleanliness.
- Read board flash codes on two-stage or variable-speed models, if equipped.
- Leak-search with an electronic detector, bubbles or a nitrogen pressure test if the charge is low.
Red flags in a quote:
- “Just needs a top-off” with no leak search.
- A compressor replacement quoted without amp or winding tests.
- Refrigerant added without measuring superheat or subcooling.
Symptom, cause and what to do
| Symptom | Likely cause | DIY action | Technician job |
|---|---|---|---|
| Nothing runs indoors or out | Thermostat, batteries, breaker | Check settings, replace batteries, reset breaker once | Low-voltage wiring, transformer, fuse on control board |
| Indoor fan runs, outdoor unit silent | Outdoor breaker or disconnect, contactor, capacitor | Check outdoor breaker and disconnect | Test and replace contactor or capacitor |
| Outdoor unit hums, fan doesn’t spin | Failed capacitor or fan motor | Turn off power at the disconnect, then call | Replace capacitor or fan motor |
| Ice on lines or indoor coil | Dirty filter, low airflow, low refrigerant | Replace filter, run fan only to thaw, open vents | Check charge, leak search, blower check |
| Runs constantly, air only slightly cool | Low refrigerant, dirty coils | Replace filter, rinse outdoor coil | Leak search, coil cleaning, charge correction |
| Cooling stops, water near indoor unit | Clogged condensate, tripped float switch | Clear condensate line | Clear trap, replace pump or switch |
| Works mornings, quits on hot afternoons | Dirty condenser, weak capacitor, high-pressure trip | Clear debris, rinse coil | Test capacitor, check pressures and fan |
| Outdoor board flashing a code (some models) | Pressure or compressor protection lockout | One power-cycle reset | Interpret code, fix root cause |
| Breaker trips when compressor starts | Shorted or grounded compressor, bad capacitor | Do not keep resetting | Compressor winding tests, hard-start kit or replacement |
Rheem air conditioner not cooling repair cost
Typical US prices, including parts and labor, in 2026:
| Repair | Typical cost | Notes |
|---|---|---|
| Air filter | $10 – $40 | DIY |
| Thermostat replacement | $30 DIY – $350 installed | Smart or EcoNet models cost more |
| Service call / diagnostic | $90 – $200 | Often credited toward the repair |
| Run capacitor | $120 – $350 | Part is cheap; most of the cost is labor and trip charge |
| Contactor | $150 – $350 | |
| Condensate drain clearing / float switch | $100 – $250 | |
| Outdoor fan motor | $350 – $800 | |
| Condenser coil cleaning | $100 – $250 | |
| Leak search | $200 – $500 | |
| Refrigerant recharge (R-410A) | $200 – $700 | Price depends on pounds needed |
| Refrigerant recharge (R-454B, on 2025+ units) | $250 – $800 | |
| Minor leak repair (Schrader core, braze joint) | $200 – $600 | Plus recharge |
| Evaporator coil replacement | $1,200 – $2,800 | Parts often under warranty; labor not |
| Compressor replacement | $1,800 – $3,500+ | Part often under warranty; labor and refrigerant extra |
If the system is more than 12–15 years old and needs a compressor or coil, get a quote for replacing the whole system before you commit to the repair.
Related codes
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- Rheem Heat Pump Outdoor Fan Not Spinning: Causes & Fixes
- Rheem Heat Pump Breaker Keeps Tripping: Causes & Fixes
- Rheem Heat Pump Short Cycling: Causes, Fixes & Costs
- Rheem Heat Pump Runs Constantly: Causes, Fixes & Costs
- Rheem Heat Pump Flashing Light: Causes & Fixes
- Rheem Furnace Blower Not Running: Causes & Fixes
- Rheem Furnace Leaking Water: Causes, Fixes & Costs
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Frequently asked questions
Why is my Rheem AC running but blowing warm air?
If the indoor blower runs but the air is warm, the outdoor unit is usually not doing its job. Common causes are a failed capacitor, a stuck or burned contactor, a tripped outdoor breaker or a refrigerant leak. Go outside and check whether the outdoor fan and compressor are running.
My Rheem AC coil is frozen. What should I do?
Set the thermostat to Off and the fan to On so the ice melts. This can take several hours. Replace a dirty filter and open any closed registers. If the coil freezes again, a technician should check the refrigerant charge and blower operation.
Can I add refrigerant to my Rheem AC myself?
No. Refrigerant work requires EPA Section 608 certification. A low charge also means there is a leak, and topping it off without finding the leak only delays the problem. A technician should locate and repair the leak before recharging.
Does Rheem's warranty cover a not-cooling repair?
Rheem's limited warranty usually covers parts such as compressors, coils and capacitors for 10 years on registered units, often 5 years if unregistered. Labor and refrigerant are typically not covered unless you bought an extended labor plan. Check your registration and warranty certificate.
How long should my Rheem AC take to cool the house?
A properly sized, working system typically cools the air leaving the registers 15–20°F below the room air. It should lower the indoor temperature about 1–2°F per hour on hot days. If it never catches up when it is under 95°F outside, have it checked.