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Thread: How to check if AC compressor is working or not?

  1. #1
    Join Date
    Aug 2005
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    2000 328i, Automatic

    How to check if AC compressor is working or not?

    Can somebody tell me how to find out if the AC compressor is working or not? I have 2000 328i and when I turn on the AC it just blows air. It's not hot or cold, it's feels like the air from the outside is blowing in. I would like to check if the AC compressor is working or not. Is there a way to find out if it’s working or not? I do not hear any noise or hear the engine rev up when I turn the AC on but I want to be sure it’s the AC compressor before changing it. Any other comments on how to diagnose the problem? Thanks in advance.

  2. #2
    Join Date
    May 2005
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    miami
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    328i
    i am having the same problem...i also would like a answer..mine just blows air...but it is not cold...

  3. #3
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    Just look at the pulley in front of the a/c compressor. If the pulley spins the same speed as the the belt then compressor clutch is working, if the pulley is not spining at all when a/c is on then something is wrong. However, it is not always the compressor. For the compressor to kick on a few pre-existing things have to happen to satisfy the the required conditions. For examples the high and low pressure switch, the compressor clutch has to be ok, the relay that send power to the compressor and etc...

    have fun

    Alex

  4. #4
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    2000 328i, Automatic

    How to check if AC compressor is working or not?

    Thanks Alex. I checked and the pulley is not spinning. What I did was put the AC on and lowered the temp. to 59 with all the windows opened. But as you said the correct condition have to be there to have it spin. So can some one please tell me the process of making sure it is the AC compressor and not anything else that is broken? Thanks in advance.

  5. #5
    Join Date
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    Austin Tx
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    2003 BMW 330i
    First check to see if when you turn the AC on the clutch of the AC Compressor is getting current should read 12V when AC is on, if it doesnt then it could be line pressure there is a little switch above the line going into the Condinser that senses if there is not enough pressure in the lines (which means if it is low you have a leak) and it wont let the compressor come on when low to avoid burning it up.
    Upload your pictures and whatever else you like
    http://www.peoplesrevolt.com

  6. #6
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    CT, USA
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    2000 328i, Automatic

    How to check if AC compressor is working or not?

    Thanks Striker169 for that information. Now I am going to ask a very basic question. How do I do what you said? I was look at where the compressor is and it’s hard to reach it and check anything. Is there a wire I can plug into to check for the 12v? I looked in the Bentley and could not figure out how to do it. Thanks in advance.

  7. #7
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    2000 328i, Automatic

    How to find out if AC Compressor is getting 12V?

    Can some one please help me with steps to check if the AC compressor is getting 12V? Thanks in advance.

  8. #8
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    I'm not a mechanic who works at a car dealership, so I can't tell you the exact wires to check. However, there's must be a connector on the compressor. Unplug the connector, find out which is ground, then using a volt meter to check the other wires against your ground, write down the voltages before and after you activate the A/C button on the control. If there's some difference then your compressor clutch is bad, if there's no difference then it could be so many things like, relay, temperature switch, high low pressure etc...And you still don't know the condition of your compressor.

    You're better off bring it to a trusted BMW mechanic......

  9. #9
    Join Date
    Oct 2005
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    00 740il silver
    Well I think with any ac problem you should check to see if you have enough
    freon in the system. With low freon or none at all you will not have the compressor turn on also. Any shop and check freon level, then go from there.

  10. #10
    Join Date
    Jun 2007
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    Manassas VA
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    1985 M635CSI 2005 K1200G

    Normally the easiest way to reach the compressor is from the bottom of the E46, I do recommend following some of the previous instructions, most commonly I find that its low in Freon, this is in part caused by 134A having a smaller molecule size than R12 and it can easily find escape routes thru connections or a big gaping hole.

    In process of elimination,
    Step 1. Get Case of Beer Put it on ICE.
    Step 2 find a shady spot part the car put the AC to coldest setting and turn the fan all the way up and take it off cabin recalculate
    Step 3 connect pressure gauge to low side (most commonly found up on the firewall passenger side)
    Step 4 Add about 2 ounces of Freon and see if the compressor kicks on. (this is most notable when you have your head in a 200 Degree engine compartment and you hear a big click and a putter putter weeerr sound)
    Step 5 Stop adding Freon!!!! if you over fill the system it could be pretty bad for you and all the parts in the system.
    Step 6 if it just needs to be topped off with Freon continue to do so Less is better(see below)
    Step 7 Clean up and start drinking beer put on ice in Step 1



    now from the steps above Normal pressure on a 75 Degree day should be in and about 38 PSI or the Blue zone on most gauges.
    Remember a little less is better for R134A more is bad.

    if for some reason you don’t get the compressor to kick on check the fuses (sometimes found in the glove box) also make sure your looking at the right part spinning, I had a buddy mistake the alternator for the AC compressor

    more complex things to check, leads to the compressor
    Magnetic Clutch and operation (grab a lead from the battery and see if the clutch engages.

    High and low pressure switch.

    AC Control on the dash

    Still not working
    refer to Step 1 and start drinking ice cold beer. Call the dealer and get your wallet cleaned out!

  11. #11
    Join Date
    Jan 2006
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    Jacksonville,Fl
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    03 330i
    As crazy as it sounds I just had mine repaired at the dealer and it turned out to be the thermostat that caused the air to turn warm after 20 minutes of driving. If I would of known that.... I would have done it myself for $70 instead of paying $400. THE STEALER GOT ME AGAIN!

    Kevin

  12. #12
    Join Date
    Mar 2006
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    Albany, NY
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    Black ZHP Sedan 6spd
    AC is designed to run at a very specific pressure. Do not fill the system without proper gauges. Take it to an independent shop that specializes in European makes, they should be able to tell you pretty quickly.
    128i

  13. #13
    Join Date
    Aug 2005
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    CT, USA
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    2000 328i, Automatic
    Thanks for the reply. I still have not gotten it fixed. In the summer I just park it in the garage. I think I will take it in to some auto shop that can do AC work and have them fill it.

  14. #14
    Join Date
    Dec 2005
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    Santo Domingo Dominican Rep.
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    1997 BMW 318 is Supercharged

    Question

    Hi gentlemen
    I have some temperature issues but the compressor seems to work fine, refrigerant R134Aa measurement are perfect and the micro filter I changed a few days back in fact it was filthy, but the temperature issue persists. BTW my bimmer is made in Germany not a USA version and it came without a secondary condenser fan, only the primary radiator fan which is electric, not belt driven
    The issue consists as follow;
    When I stop on the street light the temperature of the A/C decreases its could, it becomes between fresh and cool, if I bring the RPM to about 900 to 1000 the temperature lows down and the A/C cools great. When the car is running the A/C cools great too. This temperature issue only happens when the car is in idle, no matters if the car is geared or in neutral (automatic transmission), when the car is idling at 800 RPM it will only blow fresh to cool air, more fresh than cool No maters if the contrl is set on recirculation mode or fresh air.
    Blower performs perfect too, as every control on the digital A/C control unit.
    I hope I find a solution with the help and suggestions from you guys
    Thx

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