What Typically Causes the Heating or AC to Stop Working?

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.


Next Step

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Recent Heating AC Inspection reviews

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Ben

42 years of experience
1589 reviews
Ben
42 years of experience
Kia Soul L4-1.6L - Heating AC Inspection - Houston, Texas
Ben is the consummate professional - knowledgeable, but additionally friendly and personable. I appreciate his honesty and willingness to help.
Volkswagen Beetle - Heating AC - Houston, Texas
i am well satisfied with Mr Smith working on my car(s). He replaced the Jaguar fuel pump like an expert, and then he diagnosed the VW bug ac compressor and fixed it on the spot. I would recommend him to anyone with a car issue

Diana

19 years of experience
130 reviews
Diana
19 years of experience
Hummer H2 V8-6.0L - Heating AC - Brooklyn, New York
Diana is a pro. She made sure everything was ready beforehand, and arrived early, ready to go. She knew her stuff and took the old headers off my Hummer H2 in half the time any other mechanic quoted me. Highly recommended!
Saab 9-3 - Heating AC - Fords, New Jersey
Very professional, prompt and courteous. Knowledgeable in her trade, thorough and informative in description of diagnosis.

Peter

44 years of experience
1397 reviews
Peter
44 years of experience
Saab 9-3 L4-2.0L Turbo - Heating AC - Phoenix, Arizona
He knows what he's doing. Very polite and explained everything. I would no doubt use him again. I highly recommend him.
Mazda Miata - Heating AC - Peoria, Arizona
We are so thrilled to have found Peter as our new mechanic. He is very thorough and knowledgeable. He is also friendly, professional, and extremely honest. He explained to us exactly what services were needed on our vehicle to repair the air conditioner and provided us with an written estimate of the cost. He literally saved us thousands of dollars in repair costs. A local major competitor quoted us a repair cost of a minimum of $1,400 and said that the cost would go up to $2,400 if they discovered an additional part was required. Peter charged us only $202, plus performed the work at our home. The air conditioner in our 2004 Mazda Miata has honestly never worked so great--it always blew out warm air. We just assumed it was how that particular car was manufactured. We would highly recommend Peter to anyone who is in need of an experienced and honest mechanic.

Johnny

34 years of experience
392 reviews
Johnny
34 years of experience
Honda Accord V6-3.5L - Heating AC - Sacramento, California
Johnny showed up early to the appointment and was very thorough in his inspection. He promptly recommended the service to fix the items that are needing repairs. He was very professional and knowledgeable. I would recommend him for service.

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