Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. What Typically Causes the Heating or AC to Stop Working?

What Typically Causes the Heating or AC to Stop Working?

heating and AC

While both the heating and AC are connected - to an extent - within your car, they’re actually separate systems. Your car’s heater uses heated engine coolant to warm the air that is blown into the cabin, while the air conditioner uses a compressor driven by the engine, combined with both high pressure and low pressure lines, special refrigerant and many other components.

Potential problems with your car’s HVAC system

The potential issues here vary whether your heating has gone out or your car’s AC system is on the fritz.

Common reasons for the heating system not to work include the following:

  • Low coolant
  • Air in the coolant system
  • Malfunctioning heater core
  • Failed (or failing) thermostat

The potential issues with the AC system are different, and include:

  • Low refrigerant (will generally blow cool, but not cold)
  • Damaged compressor
  • Damaged compressor clutch
  • Damaged expansion valve
  • Damaged evaporator
  • Worn or stretched serpentine belt (required to operate the compressor and clutch)

As you can see, both systems are very different. However, if you’re experiencing problems from the HVAC controls, then it’s possible that the same issue will prevent both your air conditioning and heater from working. For instance, a failed blower motor won’t be able to blow air into the cabin. A failed fan switch will make it impossible to adjust the blower fan speed. There are a number of other potential issues, ranging from a failed relay to a blown fuse to a short in the wiring.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

Symptoms of a Bad or Failing Flexible Clutch Hose
Common signs include difficulty shifting, low clutch fluid, and feeling no resistance at the clutch pedal.
How to Find the Keyless Code on a Ford Explorer or Mercury Mountaineer
Many Ford Explorers and Mercury Mountaineers were manufactured with an option known as the Ford keyless entry keypad. Some models refer to it as SecuriCode as well. It...
P0121 OBD-II Trouble Code: TPS "A" Circuit Range Performance Problem
P0121 code definition Throttle Pedal Position Sensor/Switch (TPS) A Circuit Range Performance Problem...


Related questions

Q: heater blowing cold air most of the time, possible coolant leak

A few different items can cause the heat to be intermittent. An air bubble in the cooling system, low coolant, a heater core failure, a coolant leak, and an AC actuator can all cause the heat to go in and...

Q: AC stops working, blows warm air

Hello. Your A/C system has multiple components and sensors. It is possible that the high pressure switch is faulty. It is also possible that the blend doors for the hot and cold air are sticking and unable to open and/or...

Q: My service light says service temp. What do I need to look for?

Hi there. A low coolant level can illuminate the service light and create the heating and AC problem you have described. Check the coolant level while the engine is cold and top it off as necessary. Also, look around the...