How To Troubleshoot Common Central AC (Air Conditioner) Problems

Residential HVAC diagram

via Taylorheating.com


“Brace yourselves, warmth is coming!”

It’s getting warmer now isn’t it? Whether you like it or not, it’s not going to get any cooler so you better see if your central AC is in shape and ready to operate.

Since AC installations are considerably complicated, even residential ones, you can only do limited troubleshooting before calling an AC repair specialist (that’s us), but it’s good to know what’s wrong with your AC nonetheless so you’ll know when to call and when to fix it yourself.

Listed below are some of the more common problems and their possible causes, as well as tips on how to fix them.


AC does not power on or suddenly shuts down.

  • Check the thermostat setting and make sure that it is set to cool. If your system has a built-in timer, wait for it to complete its cycle then set it several degrees below the current room temperature. If it doesn’t work, the thermostat may need recalibration, or is already defective.
  • Check if the circuit breaker is working. An overheating compressor or faulty wiring can cause it to trip or blow a fuse.
  • Check if the furnace and outdoor condenser power switches are on.

AC not cooling.

  • Check if the filters are clean. Even if the AC is producing cold air, dirty filters can prevent it from flowing through the ductwork.
  • Check if the outside unit is working properly. A dirty condenser unit can work inefficiently and may even overload and overheat, so make sure the entire outside unit is clear of dirt and debris. If the radiator fins are bent, you can straighten it out using a radiator comb.
  • The unit may already be low on coolant or refrigerant, perhaps due to leakage.

AC blower not working.

  • For belt-driven air handlers, check if the belt is still properly connecting the motor pulley to the blower pulley. You can access the two by opening the door of the air-handler cabinet.

AC is noisy.

  • Squealing noises – this usually occurs on older units with belt-driven air handlers. Check if the belt needs re-aligning, or if it is worn and needs replacing.
  • Grinding noises – you may hear this on direct-drive motors and may be a sign that the motor’s bearings are already damaged.
  • Pinging or popping sounds – you may hear this coming from the ductwork which can be caused either by thermal expansion or a loose metal flap.
  • Rattling noises – the cover panels of the furnace might be loose. Check and tighten as necessary. You may also hear this if the compressor fan is hitting some debris.

AC is leaking.

  • The drain line or condensate pipe might be blocked. Disconnect it and clear it by blowing compressed air into it or running a wire through it.
  • The condensate pump might be dirty or malfunctioning.

Some of these problems can have multiple causes, making it difficult and time consuming to diagnose. If some of the terms and procedures above seem to escape you, call us! We have the tools and the expertise to help.

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