Tip & How-To about 2004 Audi S4

When I turn on the A/C, a visible vapor accompanied by an unpleasant odor. Is this normal? How do I get rid of the smell?

It's normal. It's simply the air condensing when the water content in the air comes in contact with cold air. If you haven't been using your A/C much, some fungal residue may build. Possible solution is to the turn up the heat on the A/C and have it blasting to kill the bacteria that resides in your A/C vent system. Another suggestion is to turn your A/C off (i.e. leave the fan on but hit ECON to turn the compressor off) for the last 10-15 minutes of your trip. This allows the A/C components (duct-work, etc.) to warm up and for the condensation that forms on them to dry off (since there is still airflow 'cause you are still driving). This will limit the bacteria growth. It is especially important to do if you are going to be leaving your car parked for any length of time and/or it is humid out (more humidity = more condensation).

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getting water in the oil

Ouch that is not something that you want.
Water can get into the oil two ways. You generally don't have to worry about one of the ways if you drive your car enough to burn off the water during normal driving. This drives off the moisture that simply comes from your engine breathing when it is not being used (cold air enters a hot engine and water condenses) and from combustion by-products. The second more destructive route is through a coolant leak due to a bad gasket, an engine crack, etc. This amount of moisture is generally going to cause serious engine issues including loss of power, oil sludging, etc. Consult your mechanic when in doubt.

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water seesm to leak from behind fan housing when it rain and after air conditoner is turned off

water dripping from a.c after being used is normal on any vehicle, its just condensation frome warm air and cold ac lines, as for rain its probably just rain water coming through the front end, however if the water is reddish or green in color it would indicate a coolant leak and would be noticable much more often.

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my a/c unit is fully charged but the freon seems to be RUNNING out of the condensation line coming from the firewall??? the a/c blows cold but i think if it keeps RUNNING out the condensation line it will stop blowing cold air...the air coming out of the vents also smells of freon...

i think what your describing is normal operation.the moisture coming out is water from the
a/c doing its job. the duct works can be cleaned with a spray cleaner sold at parts stores
if the smell is bother some.

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This water is most probably condensation dripping from the airconditioner. This condensation is formed by the warm air coming in contact with the cold A/C. No need to worry about it. Run the vehicle without the A/C and see if the "leak" stops. If it was engine coolant it would have been green or brown in color(assuming your coolant contains antifreeze)

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honda acac sometimes blows some kind of dew air throught he vents

u most likely have some condensation building up in evap box ,,need to clean it out before it gets worse,,,if u are running it on low blower ,it is going to put out mist sometimes (if the air is really cold) because of the expansion valve pulling down the tempurature

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