AC Not Cooling
If your AC runs but isn’t producing cold air, the cause is usually one of a handful of part failures. We walk through each from most to least common, with photos.
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If your AC is running but not producing cold air, the problem is usually one of a handful of common part failures. Below we walk through each cause from most to least common, with images of the actual parts from our Dallas store.
Common Causes
⚡ Bad Capacitor MOST COMMON
The capacitor stores electrical energy to start and run the compressor and fan motor. If your outdoor unit hums but the fan won’t spin, or the AC runs but only blows warm air, a failed capacitor is the most likely cause. Physically swollen or bulging capacitors are a dead giveaway.
🔌 Failed Contactor
The contactor is an electrical relay that switches power to the compressor and fan. If you hear clicking from the outdoor unit but neither the compressor nor fan will run, the contactor’s contacts may be pitted or stuck open. Over time, electrical arcing wears the contact surfaces down.
🌀 Dead Condenser Fan Motor
If the compressor is running (you’ll hear a loud humming) but the outdoor fan isn’t spinning, the condenser fan motor has failed. Without the fan pushing air over the condenser coil, the refrigerant can’t release heat and the system blows warm air. The compressor will eventually shut down on safety.
🌡️ Bad Thermostat
Set the thermostat 5°F below the room temperature and wait 30 seconds. If the outdoor unit doesn’t kick on, the thermostat may not be sending the cooling signal. Try replacing the batteries first — this fixes the problem more often than you’d think.
A severely clogged filter restricts airflow and can cause the evaporator coil to freeze. Pull your filter out and hold it up to a light — if you can’t see through it, replace it. This is a free check that can save you from buying parts you don’t need.
Quick Diagnostic Checklist
Before you replace parts, check these:
☑️ Thermostat set to COOL and below current room temperature?
☑️ AC breaker in the electrical panel switched ON?
☑️ Any sounds from the outdoor unit? (Humming, clicking, or nothing?)
☑️ Air filter clean? (Hold it to light — should see through it)
☑️ Supply vents open and not blocked by furniture?
Always disconnect power at the breaker before inspecting or replacing electrical components. Capacitors hold an electrical charge even when powered off. If you’re not comfortable working with electrical parts, bring your old part to our store and we’ll help you find the right replacement.
Watch Our Video Tutorials
🎥 How To Replace A Capacitor
🎥 How To Diagnose A Bad Contactor
🎥 What To Check When Your HVAC System Isn’t Coming On
Need the Right Part?
Bring your old part to our Dallas store — we’ll test it for free and find the right replacement.
📞 (214) 340-9421
Mon–Fri 10 am – 7 pm | Sat 10 am – 3 pm
Related Troubleshooting Guides
Looking for a replacement capacitor from a different brand? Check our HVAC Capacitor Cross-Reference Chart comparing 9 major manufacturers.
Considering full system replacement?
If your unit is 12+ years old or you’ve already replaced 2+ major parts, full replacement may make more financial sense than another repair. We’re an authorized Rheem dealer — complete systems start at $2,830.
Walk in. We’ll match it.
Bring your old part or a photo of your unit. We’ll find the replacement, test the new one before you leave, and walk you through the install if you’ve never done one.
Parts That Fix This Problem
Browse our in-stock inventory — or just bring your old part in and we will match it at the counter.
Run & start capacitors for AC unitsContactors →
Single & double pole AC contactorsCondenser Motors →
Universal & OEM fan motorsThermostats →
Programmable & non-programmableControl Boards →
Furnace & air handler boards
Not sure which part you need?
Call or text us at (214) 340-9421, or bring in your old part — we will bench-test it for free and find the right replacement.