Q: A/C and heat work intermittently

asked by on

Some times the A/C or heat will blow and the next time there won't be any air flow at all. Fuse is not blown, before I go tearing the dash out, I'd like to get more knowledge on the exact problem, thank you!

My car has 142000 miles.
My car has an automatic transmission.

Hello - I would first check for fan motor voltage coming out of the HVAC control switch. A bad contact for the fan could act as you describe. If you are consistently getting 12 volts out of the switch TO the fan motor, an electrical fault with the fan motor (worn brushes or dirty commutator on the fan motor) is the next component to check. I would recommend having a Fan Speed Control is Not Working Inspection completed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. A/C and heat work intermittently

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Diagnosing a heater core problem

A common tell tale sign of the heater core not working is the heater not providing warm heat when turning it on. You may also notice the floor being a bit damp in the event that the heater core might...

Q: A/C and heat are not working properly. Car blows heat in summer and cool air in winter.

Common causes of no cabin heat include malfunctioning blend door(s) (part of the in-dash ventilation network), a faulty or stuck heater control valve, a plugged heater core, stuck open engine cooling thermostat, collapsed hoses, and low coolant level. The cost...

Q: When replacing push rods on a Cummins 12v, they keep bending after installing new ones. Is a valve stuck or something worse?

Hello. You either have a sticking valve or the valve is hitting the piston due to the timing being off. Most of the time though the valve sticks from carbon build up in the engine. The cylinder head would need...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...