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Technical Sanden 508 Vibration At Idle Only

Discussion in 'The Hokey Ass Message Board' started by CarQuestions, Aug 8, 2015.

  1. CarQuestions
    Joined: May 24, 2015
    Posts: 105


    I have a 2007 5.3 Vortec mounted in a 1961 Cadillac. I used small block Chevy engine mounts with flat plate adapter brackets. A new Sanden 508 AC compressor is mounted to the block over the right side cylinder head and is driven by the main (single) serpentine belt. The engine is drive by wire and it uses a computer controlled throttle valve. The engine idles very smooth with the compressor disengaged.

    The problem is that the whole car vibrates w witth a buzz like high speed vibration when the AC compressor is engaged and the engine is at idle. It is like I can feel all 8 compressor pistons pumping refrigerant. It is very smooth above idle with the compressor engaged. Since the engine idle speed is controlled by the throttle valve the idle speed is constant with or without the compressor engaged so it not like the engine is lugging under when the compressor kicks on.

    The refrigerate pressures are normal and the compressor and fans cycle normally and the vibration does not seem to be affected by fans on/off or pressures.

    The compressor is installed with rubber AC hoses so it is not like the vibration is being transferred by the hard lines. I looked all over and there does not seem to be any metal to metal interference and since the engine is smooth without the Sanden engaged.

    Any suggestions?

    What should normal refrigerator pressures be?

    Has anyone out there in cyberspace had this same vibration at idle?

  2. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 30,894

    Jalopy Joker

    which way does the water pump rotate? post some pics of motor/AC set up
  3. is there a way to raise the idle when the compressor is engaged? Like through the computer.
  4. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,091


    You should not need to. It has an IAC valve, which keeps the idle the same, load, or not.

    You might want to check that.

  5. CarQuestions
    Joined: May 24, 2015
    Posts: 105


    I confirmed that the idle system is working as advertised... Idle speed stays the same when AC is on or off.

    The problem is that at idle the speed of the compressor is such that the AC compressor is turning the exact speed to cause a vibration. Just above idle it is very smooth.

    Do they sell a smaller diameter compressor pulley?

    Any AC guys out there that can give some advice?
  6. noble wanderer
    Joined: Dec 26, 2015
    Posts: 2

    noble wanderer

    Sorry comment not related to your problem but I would love to see pictures of this motor setup
  7. Brand Apart
    Joined: Jan 22, 2011
    Posts: 808

    Brand Apart
    from Roswell GA

    Even though the" pressures are good" I bet tweaking the amount of refrigerant slightly will change this, I've seen it before , it was several years ago so unfortunately I don't remember if it was undercharged or overcharged that caused it. R134is cheap as hell at big lots if u have one around $7 a can near me so you can experement and see what happens.
  8. themodernartist
    Joined: Feb 16, 2006
    Posts: 155


    Hey Car Questions,
    You may want to check with Vintage Air about using a 508 with a Vortex engine. I was inquiring with them about using their Gen-IV A/C Magnum climate control unit in my '51 Hudson and I was advised to use the 509. They had vibration problems when using the 508 with this engine. Anyway, it wouldn't hurt to e-mail or call them about this.

    This is my own designed and built compressor bracket for my LS1 engine.
    Comp Brkt, Top View 10-30-13.jpg
  9. FritzTownFord
    Joined: Apr 7, 2007
    Posts: 1,020


    Call Vintage Air. Ask for Mark in tech - they've been engineering this stuff for 40 years.
  10. themodernartist
    Joined: Feb 16, 2006
    Posts: 155


    Yeah, talk to Mark!

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