Last weekend we had some warm weather up in Seattle. After about 5 mins of driving in my '01 S4 I noticed that the A/C is not blowing out the nice cool air it did all last summer. I set the temp down the the "lo" so it should kick on the A/C. I turn the econ mode on and off and watch the RPMs and listened to the engine and did not see in difference in the RPMs or hear the anything kicking on or off.

So where should I start? What should I look for? Any help would be great. Or point me to some threads that have some good info. Thanks!

 

Where is the A/C located in the engine bay? I had my starter replaced in Nov 09 I just wonder if something may have not been installed correctly or something...

 

There seems to be two most common issues with the A/C not coming on. Either a leak in the system (look for neon green dye, or wet looking circles on your condenser), which can commonly be found at the condenser (the black radiator type thing in front of your radiator), or at various connections.
Another problem can be the A/C "Trianary" switch or the high/low pressure switch. This has a square harness running to it on the passenger side of your condenser, it can be easily accessed by removing the passenger side headlight. The job of this switch is to regulate the A/C depending on whether the pressure of the system is too high or too low. If the pressure is too high, continuing to run the A/C can damage it. If it is too low the lubricating oil will not circulate and air and water can enter the system which can also damage it. The job of this switch is to turn of the A/C if there is a problem (i.e low pressure because a rock hit your condenser). If you dont see any leaks, this can be a problem, some people will short the connector together to see if the a/c will blow cold when the switch is bypassed. The best way to check to see if your A/C is still filled with refrigerant is to buy an A/C pressure gauge and connect it to the "low" side of the two lines that run into the passenger side of the car. (There is a low pressure and high pressure side, you want to avoid the high pressure side) If there is no pressure, the refrigerant has leaked out from somewhere, if there is pressure, the switch or another damaged part is likely the culprit. If the system has pressure, do not remove any of the A/C lines (they can be identified as narrow metal lines, or thick rubber tubes with heavy duty fittings. The reason for this is that certain parts of the A/C system are under extreme pressure, and removing them can be dangerous, not to mention venting refrigerant into the atmosphere is not good.

Your "A/C" is located at a number of different places in your engine bay. First there is the condenser, (described above) there is the dryer located near the passenger side headlight (a silver canister), you have your high and low pressure lines with their fill fittings that into the passenger side of the passenger compartment, you have the compressor which is located beneath the car and is driven by a belt. Finally there is the evaporator, located inside the car, and looks similar to a smaller version of the condenser. Leaks in any of these components can cause you to loose refrigerant, and thus not have working A/C.

 

Oh wow so I have several places to look at. All I've checked so far is the fuse which is good. I will start with those other places.

 

FIrst scan for codes. The climate control unit is pretty complex and can throw a number of codes on its own. If there are no codes, then you probably have a refrigerant leak. The compressor will not kick on if you are out of refrigerant -- this sounds like what's happening.

 

I didn't know it would throw a code... I will get it scanned by my buddy's vagcom

 

If it does have a code it will probably say low pressure circuit or something like that. If it says that its still either the switch or a leak.. But itll be good to check it out, might as well.

 

The parts and locations you are describing.......are they common locations for all S4's? My V8 system is not belt driven. Direct shaft drive. I'm looking got the Hi/Lo pressure switch and the Compressor regulator valve. Can U help?

Thanks in advance.