Skip the auto shop - Our mechanics make house calls

Q: A/C control messed up.

asked by on

Auto mode - A/C blows hot air from the bottom/foot vents even when it is 80 degrees outside. Not normal. Manual controls will blow correctly, however, if it is really cold outside the middle dash vents blow cold air from the inside bottom corners. Warmer air blows out from most of the dash vents. Also, if I turn the heat up to max only warm air blows - not hot. I've tried the different hot/cold settings from within the iDrive system. This was never needed prior to the AUTO mode function doing its crazy thing. I've been told it may be the controller. Weather has been relatively good so not very annoying, however, when it did get really cold it was a little uncomfortable inside. Also, the fan motor by the radiator runs at high speed whenever the A/C is on. Makes a very loud annoying sound at low speeds. This may be another problem caused by the controller. Any suggestions?

My car has 152000 miles.
My car has an automatic transmission.

The system is controlled electronically and consequently the controller is a possibility. But, to condemn the controller, there is a long sequence of diagnostic steps (from the Factory Service Manual) that have to be performed. Typically, in diagnostics of this sort, a bi-directional scan tool is used to remotely command operation of the various HVAC modes. If the controller does not function as commanded by the scan tool, throughout the diagnostic sequence, at that point it would be condemned and replaced. There are also blend doors and a heater control valve which could be implicated in the problem you are describing. For example, if a heater control valve is sticking, along with a blend door malfunction, you could have hot air delivered at the same time that the A/C system is on. If you request a diagnostic on the system performed by a certified Mechanic, dispatched by YourMechanic right to your location, the responding certified mechanic will get this resolved for you. The diagnostic to request is HVAC system diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 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
  1. Home
  2. Questions
  3. A/C control messed up.

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: Just had timing chain replaced on 2012 qx56 and they called" -- dealer called and said while fixing the timing belt that my ac pum

Hi there. It does seem kind of suspicious that your vehicle went in with ac and now it doesn't work. I completely understand how you feel and hope to help you fix this. However, component failure can happen at any...

Q: About how much time should it take a certified bmw mechanic to analyse the cause of a squealing noise from the engine?

Over time, your car's engine belts may become worn causing them to stretch. When this happens as you press the gas pedal and the belt goes from a relatively low speed (at idle or when first starting the car, no...

Q: Engine Code P0016

The P0016 code is most likely due to the engine sludge build up as the VVT (variable valve timing) system is control with oil pressure. In regards to the engine flush, I whole heartedly agree with Toyota. The number of...

Related articles

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...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...