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  1. #1
    Active Member One Ring
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    Nov 10 2018
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    Largo, Fl

    2006 B7 S4 25quattro AC problems NEWBIE

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    Okay boys, newbie in need of technical assistance

    I bought this car recently knowing VERY little about this car and Audi's in particular. 06 S4 25quattro. Car is #152 of 250. 134kmi, H&R springs, 19x8.5 wheels, super clean interior, etc. I have poked around on the Audizine site and really like it!

    I have a few issues with this car and I am sorting them as I can. Everything so far has been the typical B7 S4 problems. I replaced the clutch, and dual mass flywheel, but in the process the damn cross bar for the shifter broke. Ugh, I have a plan of attack for that, just waiting on parts to arrive. DIY mod is in the works!

    I have the leaky valve cover woes as well, which hope to tackle ASAP.

    The real problem I have currently is the AC. I live in Florida and its usually hotter than Satan's butthole 10 months out of the year here.

    AC repairs I've done so far:
    I replaced the fan control module (the one right up front) thinking it was bad, causing the cooling fans to not turn on, which wouldn't allow the compressor to engage the wobble plate.
    Nothing. Both cooling fans eventually come on if the car idles for 20 mins

    I checked the freon level, it was super low. I thought Bam! So I vacuumed the system down for an hour. zero leaks, and added about 1.5 cans of freon. The high side would never go above 90 (which indicates the compressor isn't well compressing the freon).

    I have no econ light on, I have no fuse popped. Could I have a bad high pressure switch? Is there a relay or control module for the variable compressor?

    Im open to suggestions, ridicule, advice, whatever.

  2. #2
    Senior Member Three Rings Clun9's Avatar
    Join Date
    Oct 09 2008
    AZ Member #
    34017
    My Garage
    B6 S4, B8.5 S4 & Unicorn 337
    Location
    Union City

    Check the spline on the AC compressor. Those usually wear out and spins freely.
    Memoryfab - Rare Wheels Everyday MTechnica - Your Resident 3-Piece Bespoke Wheel Designer

    MK4 337 | B6 S4 | B8.5 S4

  3. #3
    Senior Member Three Rings Velox's Avatar
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    Mar 30 2016
    AZ Member #
    371041
    My Garage
    audi
    Location
    Oranjestd

    Compressor failsafe plate is supposed to break before your splines are damaged. Not that it always works.
    But I would get VAG , and check for compressor shut of codes, and if no present use vag to check if compressor works properly.

  4. #4
    Senior Member Four Rings VinnysS4's Avatar
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    Nov 12 2015
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    364349
    Location
    Oregon

    What wad the temp outside while filling the freon? You should have 1psi for each degree F worth of ambient temperature. If your psi does not change when you turn the a.c. on, it's not working properly. Check in VCDS if the a.c. signal changes while cycling the AC

    Sent from my SM-N920V using Tapatalk
    1997 VW GTI VR6 (sold), 2003 Audi RS6 (sold), 2010 Audi A4 2.0T (RIP Totaled on 11/2/2015 ) 2005.5 Audi S4

    My build log
    http://www.audizine.com/forum/showth...-s-s4-timeline

    Texpoops "Correct, but a half inch difference isnít going to accelerate wear by much. Iím sure the front dips that much with a fatty in the front"

  5. #5
    Active Member One Ring
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    Nov 10 2018
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    Quote Originally Posted by Clun9 View Post
    Check the spline on the AC compressor. Those usually wear out and spins freely.
    its spins fine, shaft is connected

  6. #6
    Active Member One Ring
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    Quote Originally Posted by VinnysS4 View Post
    What wad the temp outside while filling the freon? You should have 1psi for each degree F worth of ambient temperature. If your psi does not change when you turn the a.c. on, it's not working properly. Check in VCDS if the a.c. signal changes while cycling the AC

    Sent from my SM-N920V using Tapatalk
    temp outside was 80deg. I have never heard of a compressor working with a high side of 90psi. Its not compressing the freon at that pressure. I will have to get a VAG or VCDS. I do have access to a snap on scan tool with the german add on.

  7. #7
    Senior Member Four Rings VinnysS4's Avatar
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    Nov 12 2015
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    Oregon

    Didn't mean to lead you wrong. See below post
    1997 VW GTI VR6 (sold), 2003 Audi RS6 (sold), 2010 Audi A4 2.0T (RIP Totaled on 11/2/2015 ) 2005.5 Audi S4

    My build log
    http://www.audizine.com/forum/showth...-s-s4-timeline

    Texpoops "Correct, but a half inch difference isnít going to accelerate wear by much. Iím sure the front dips that much with a fatty in the front"

  8. #8
    Senior Member Four Rings VinnysS4's Avatar
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    Nov 12 2015
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    Oregon

    Quote Originally Posted by corner worker View Post
    temp outside was 80deg. I have never heard of a compressor working with a high side of 90psi. Its not compressing the freon at that pressure. I will have to get a VAG or VCDS. I do have access to a snap on scan tool with the german add on.
    That pressure is what you should see on both high and low side with the compressor off. 1 psi per degree F is about what you'll see. 90 psi sounds about right, maybe a bit high at 80 degrees, but certinally within a reasonable amount. Once the compressor kicks on, those will change drastically.
    I don't know what spec is for the high side, but If the numbers do not change, either you have no signal getting to the compressor from the ecu, or something is stopping it from sending the signal to turn on.
    (Or a bad compressor)

    And it doesn't matter what scan tool you use. If it gives you the data pids you need. I have a vast array of cables and programs from VCDS, Snap on Verus, to Galletto. I still prefer my ELM327 for regular codes and VCDS for anything else on a vw/audi.
    Sent from my SM-N920V using Tapatalk
    1997 VW GTI VR6 (sold), 2003 Audi RS6 (sold), 2010 Audi A4 2.0T (RIP Totaled on 11/2/2015 ) 2005.5 Audi S4

    My build log
    http://www.audizine.com/forum/showth...-s-s4-timeline

    Texpoops "Correct, but a half inch difference isnít going to accelerate wear by much. Iím sure the front dips that much with a fatty in the front"

  9. #9
    Veteran Member Three Rings a4lownslow's Avatar
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    Feb 12 2014
    AZ Member #
    144887
    My Garage
    2007 Audi A4 2.0T
    Location
    Hudson WI

    I bet your compressor has failed and like stated above the breakaway plate is broke. Probably looks like this..IMG_4956.jpg


    Sent from my iPhone using Audizine

  10. #10
    Active Member One Ring
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    Quote Originally Posted by a4lownslow View Post
    I bet your compressor has failed and like stated above the breakaway plate is broke. Probably looks like this..IMG_4956.jpg


    Sent from my iPhone using Audizine
    I hope not. I will like to try every option first before replacing the compressor.

  11. #11
    Active Member One Ring
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    Nov 10 2018
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    Quote Originally Posted by VinnysS4 View Post
    That pressure is what you should see on both high and low side with the compressor off. 1 psi per degree F is about what you'll see. 90 psi sounds about right, maybe a bit high at 80 degrees, but certinally within a reasonable amount. Once the compressor kicks on, those will change drastically.
    I don't know what spec is for the high side, but If the numbers do not change, either you have no signal getting to the compressor from the ecu, or something is stopping it from sending the signal to turn on.
    (Or a bad compressor)

    And it doesn't matter what scan tool you use. If it gives you the data pids you need. I have a vast array of cables and programs from VCDS, Snap on Verus, to Galletto. I still prefer my ELM327 for regular codes and VCDS for anything else on a vw/audi.
    Sent from my SM-N920V using Tapatalk
    Right on. The car is about 60miles from me currently (Front bumper getting repainted). Once I get it back in my possession, I will try to connect to the scan tool. If the compressor shit the bed, I will be selling a S4 25quattro CHEAP...lol.

  12. #12
    Senior Member Four Rings VinnysS4's Avatar
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    Oregon

    Quote Originally Posted by corner worker View Post
    Right on. The car is about 60miles from me currently (Front bumper getting repainted). Once I get it back in my possession, I will try to connect to the scan tool. If the compressor shit the bed, I will be selling a S4 25quattro CHEAP...lol.
    Lol.
    I feel ya as my car has been a boatload of problems from day 1. The compressor isn't tooooo hard to swap. It is an involved process tho. Takes a couple of hours, a few choice words, and some cold ones.

    Sent from my SM-N920V using Tapatalk
    1997 VW GTI VR6 (sold), 2003 Audi RS6 (sold), 2010 Audi A4 2.0T (RIP Totaled on 11/2/2015 ) 2005.5 Audi S4

    My build log
    http://www.audizine.com/forum/showth...-s-s4-timeline

    Texpoops "Correct, but a half inch difference isnít going to accelerate wear by much. Iím sure the front dips that much with a fatty in the front"



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