QUESTION: With cooler weather here, I'm wondering if there's anything one should do before putting their air conditioner to bed for the winter. Should I have it serviced? What about turning it on once in a while?

ANSWER: This might come as a surprise, but most automotive air conditioners will be chugging along, without being asked for, during the winter months whenever the defroster is in use. Air conditioners remove moisture from the air, evidenced by the puddle of water that is often seen beneath a vehicle after it is parked. It may sound crazy to be making cold air as you sit shivering behind a foggy windshield, but your heater has far more capability than the air conditioner, so the blend of the two systems results in warm dry air, which is preferable to hot wet air blowing against the windshield.

It's always a good time to consider performing needed maintenance, but servicing the a/c system now may not be necessary. If it was recently pumping out cool air, you can assume the refrigerant level is adequate, making leak detection and recharging unnecessary. Several other service tasks are doable at home. They include checking the compressor drive belt, a visual inspection of refrigerant lines, hoses and fittings, removing debris from the condenser and evaporator housing drain, and possibly applying a fungicide to the evaporator and its enclosure.

The compressor drive belt should be tight, oil-free, and have little or no cracking or glazing. If a dirty haze is evident around a refrigerant fitting or hose, some leakage is occurring. Leaking refrigerant doesn't leave a trace, but the oil carried with it creates a slightly sticky surface to attract dirt. A little dirt haze is tolerable, but if wetness is also evident, a repair will eventually be needed.

Proper airflow through the condenser (a radiator-like device in front of the actual radiator) is important. Cleaning leaves, paper and grit from the fins will be helpful in many ways. If the system is draining water nicely and no objectionable cabin odors are noticed, the often difficult-to-access evaporator housing drain is probably functioning OK. It's typically located on the front, lower passenger side of the firewall and may be a rubber tube or a plastic protrusion.

If you're noticing a stinky-socks type of odor jrom the vents, fungus buildup is the cause. The evaporator, a phone book-sized finned device located deep behind the instrument panel, attracts moisture. Mix this with some airborne particles and a little warmth, and a stinky slurry often develops. A professional cleaning may be needed in stubborn cases. This involves accessing the evaporator housing from every possible angle, possibly drilling a few holes, and fogging the contents with fungicide.

Lesser odors may be reduced by spraying perhaps a third of a bottle of glass cleaner (containing ammonia) into the fresh air inlet (a plastic grill at the outer base of the windshield), while the blower is set to high speed, with the heater enabled. Placing an old towel in front of the heater outlet will help insure damage to vehicle upholstery doesn't occur.

(Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose. E-mail under-the-hoodearthlink.net. He cannot make personal replies.)