Q: The air conditioning in our Equinox really stinks when I fire it up, though the smell does goes away after a few minutes. What can be done to fix this?
_Alicia O.
A: Alicia, what you're smelling is likely microbial growth on the air conditioning system's evaporator core. When the air conditioner is in use, condensation forms on the surfaces of this cold, honeycomb-like device, which is located in a plastic housing deep within the instrument panel, creating a perfect environment for bacteria to flourish. Other possible causes for the odor include foreign debris (usually leaves) decomposing in the air intake system or a water leak that has saturated carpet or upholstery.
Some General Motors vehicles come with a heating, ventilation and air conditioning (HVAC) after-blow function imbedded in the system software, which can be enabled for folks in high humidity areas via skilled use of a pro-grade diagnostic scan tool. This function continues to run the HVAC blower fan for several minutes after vehicle shut-off, helping to dry off the evaporator surfaces. Drivers of all vehicles can employ a similar but more proactive strategy by selecting outside air (normal versus recirculation) and shifting to vent with a high blower speed for the final five or more minutes of operation.
If the above doesn't do the job, a professional disinfecting process may be needed. A home treatment may also be attempted with a can of Lysol.
With all windows down, the system set to vent and outside air, and blower set to high, spray perhaps a half can of Lysol into the air intake at the outside base of the windshield. You can determine which part of the plastic grille has the best suction by running a test with a sheet of paper. To play it safe, I'd lay an old beach towel over the instrument panel, somewhat muffling the vents and thereby avoiding the chance of traces of the cleaner reaching the upholstery. After finishing, you'll want to let the vehicle air out for several hours before use.
Q: Our 2011 Audi A4 has begun making a humming noise that seems to be coming from behind the steering wheel. It seems to get louder as speed increases and varies when making turns. Your advice is appreciated prior to taking it to the dealer.
_Thai N.
A: The first thing to check in a case like this is irregular tire wear. If the tires, particularly front, exhibit a saw-tooth pattern across the tread (rubbing a hand back and forth across the tread helps to detect it) this may be the cause of the noise. Tire rotation or replacement may be needed, along with an alignment check. Audi released a service bulletin addressing similar noises in December 2015 suggesting the cause could also be faulty wheel bearings. Your comment that the noise changes during turns seems to point this way. If the noise increases when turning a given direction, the opposite side wheel bearing is the suspect.
