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

41 years of experience
1410 reviews
Ben
41 years of experience
Volkswagen Beetle L5-2.5L - 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
Nissan Altima - Heating AC - Houston, Texas
Incredibly nice and took the time to show me the problem, including comparison pictures between my unit and what a new unit should look like.

Peter

43 years of experience
1321 reviews
Peter
43 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.

Pedro

31 years of experience
78 reviews
Pedro
31 years of experience
Chrysler PT Cruiser L4-2.4L - Heating AC - Portage, Indiana
Pedro was wonderful! He was early first and foremost. He was very professional and he explained things to me. He worked quickly and was very thorough. Very happy with his service.

Manuel

32 years of experience
580 reviews
Manuel
32 years of experience
Ford Taurus V6-3.0L - Heating AC - Long Beach, California
Good guy. Knows his stuff. Knowledgeable and straightforward with diagnostics and repair costs. I’d love to work with him again! Thank you Manuel!

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