News

Who’s ready for a Q and A about auto A/C? At Master Auto Repair in St. Louis, MO, we do hear questions about auto A/C from time to time, so we hope we can clear a few up today. 

Q: Why is there an obnoxious smell from my car’s A/C vents? 

A: It’s inevitable that water will condense in the A/C system…at the evaporator, around the blower and inside the vents and ductwork. Water means a ripe environment for dust, pollen and mildew to collect, and chances are that sour smell is coming from those. Replacing the car’s cabin air filter can help quite a bit. If the smell persists, try running the A/C on the “recirculate” setting, then spray a generous amount of an odor-killing agent such as Lysol into the air intakes below the windshield wipers. Run the car for about ten minutes, A/C on and windows down, then repeat. 

 

Q: How often does my system need to be recharged with refrigerant? 

A: Your car’s A/C operates on the exact same principle as a refrigerator, but it’s subjected to vibration, extremes of heat and cold and other harsh conditions that a refrigerator would never experience. Even on a late model car, the A/C system’s hoses, seals and gaskets are permeable and will allow a certain amount of refrigerant to escape. It’s estimated that a system will lose 5 to 15 percent of its refrigerant over a year’s time. 

 

Q: My A/C isn’t blowing as cool as it should be; sometimes it only blows cool when the car’s moving. What should I do? 

A: Nine out of ten times, A/C that isn’t much cooler than ambient air is due to low refrigerant. Don’t keep operating the system with low refrigerant; this can put undue strain on the system’s components and cause it to fail. Refrigerant also contains a lubricant which is important to keeping the system operating properly. 

 

Q: What’s the liquid leaking from under the car while the A/C is running?

A: Like a refrigerator, an automotive A/C system runs on a cycle of compression and of refrigerant. That cycle also means condensation and evaporation, which is what actually generates cold air. The liquid leaking from under the car is just excess water that condenses when the A/C is switched on. It’s important that the rubber drain tube for condensate stays open to drain freely. 

 

Q: When the A/C is running, I hear a metallic clunk at regular intervals from under the hood. What is that noise? 

A: Your A/C compressor is designed with a magnetic clutch which prevents it from running continuously if the system is low on refrigerant. Chances are that the clunk you hear is the compressor cycling on and off at regular intervals. 

 

Q: My A/C system cools only intermittently. Why? 

A: In these cases, there’s a good chance that the system might be freezing up. Air and moisture inside the system can allow ice deposits to form, freezing and blocking internal passages. In these cases, a vacuum pump can help purge the system of moisture and air bubbles. 

 

Q: My system was recently recharged with refrigerant, but still blows only hot air. Help!

A: This can occur when the Blend Air damper is stuck in the Heat position; sometimes, you can plainly hear a clunk from behind the dashboard as the damper closes. It can also be a problem with an automatic climate control system…which can be pretty complex to diagnose and repair. 

 

Did these Q & A’s help with any A/C problems you might be experiencing? If not, give us a call at Master Auto Repair or schedule an appoitment in St. Louis, MO and let us help!