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  1. #1
    Whiskers
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    What does the A/C Compressor Clutch Relay do?

    Would this item cause my compressor to just stop running after a few moments of just turned on? Thanks!


  2. #2
    gale
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    Re: What does the A/C Compressor Clutch Relay do?

    Not necessarily. It could also be cutting out if the freon is under or over pressurized. If you want to check the relay, it's behind the left footwell speaker. It's should be white & is the smallest of the 3 components back there. You can open up the plastic case with some tiny jewelers screwdrivers & look to see if the points are burned. If so, sometimes they can be sanded with a nail file to add some more life to them.<p>gale<br>92 735i<p><i><br>Would this item cause my compressor to just stop running after a few moments of just turned on? Thanks!<p></i><br>

  3. #3
    Whiskers
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    Re: What does the A/C Compressor Clutch Relay do?

    I thought that Clutch Relay was next to the CCM and LKM? Atleast according to a labeled picture that I obtained. BTW, just filled the freon. Thx<p><br><i><br>Not necessarily. It could also be cutting out if the freon is under or over pressurized. If you want to check the relay, it's behind the left footwell speaker. It's should be white & is the smallest of the 3 components back there. You can open up the plastic case with some tiny jewelers screwdrivers & look to see if the points are burned. If so, sometimes they can be sanded with a nail file to add some more life to them.<p>gale<br>92 735i<p><br>Would this item cause my compressor to just stop running after a few moments of just turned on? Thanks!<p><br></i><br>

  4. #4
    Rainman
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    It could but its not likely, On your 750il it has

    <i>a module know as the airconditioning lock sensor control module and what this does is compare the speed of the compressor to the engine speed, if it varies more than 30% it will shut down the compressor to avoid belt breakage. The 750s up till 92 had this feature. Fore example if the belt tension is too loose then the compressor can slip enough to cause this to shut it down. Or the example that bmw uses is if you go through a puddle or splash water onto the belt then the compressor can possibly slip enough for this also.<br>Or you could have overcharged the system with freon and have the same thing occur or the high pressure switch could shut if off on an overcharge also. Any number of things can trigger this module also such as excessive engine temps anytime its above 240 it will pulse the compressor clutch. If it hits 250 the clutch disengages until the engine is restarted.... I have seen this problem frequently on mercedes but the only bmw's that I am aware of that have it are the 750s and 850s till 92<br>Would this item cause my compressor to just stop running after a few moments of just turned on? Thanks!<p></i><br>

  5. #5
    gale
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    Re: What does the A/C Compressor Clutch Relay do?

    What year is yours? Bentley's shows the A/C clutch relay in the fuse box next to the CCM like you say, for 92-94, 88-91 is in the kick panel.<p>If you just filled it, could it be cutting out from over pressurizing? If you leave the A/C on, does the clutch cycle back on by itself after cutting out? Could it have crud in the expansion valve or a faulty expansion valve?<p>I'm not much of an A/C expert. Perhaps ask Fareed or Tom Meacham or others.<p><i><br>I thought that Clutch Relay was next to the CCM and LKM? Atleast according to a labeled picture that I obtained. BTW, just filled the freon. Thx<p><p>Not necessarily. It could also be cutting out if the freon is under or over pressurized. If you want to check the relay, it's behind the left footwell speaker. It's should be white & is the smallest of the 3 components back there. You can open up the plastic case with some tiny jewelers screwdrivers & look to see if the points are burned. If so, sometimes they can be sanded with a nail file to add some more life to them.<p>gale<br>92 735i<p><br>Would this item cause my compressor to just stop running after a few moments of just turned on? Thanks!<p><br></i><br>

  6. #6
    Whiskers
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    Re: What does the A/C Compressor Clutch Relay do?

    It is an '89 750iL. And no it does not cycle back on. Only if I turn off the engine and turn it back on. It did this when freon was low and even when I just filled it up. Valves? Crud? I don't know. How would I check? Thanks again!<p><br><i><br>What year is yours? Bentley's shows the A/C clutch relay in the fuse box next to the CCM like you say, for 92-94, 88-91 is in the kick panel.<p>If you just filled it, could it be cutting out from over pressurizing? If you leave the A/C on, does the clutch cycle back on by itself after cutting out? Could it have crud in the expansion valve or a faulty expansion valve?<p>I'm not much of an A/C expert. Perhaps ask Fareed or Tom Meacham or others.<p><br>I thought that Clutch Relay was next to the CCM and LKM? Atleast according to a labeled picture that I obtained. BTW, just filled the freon. Thx<p><br>Not necessarily. It could also be cutting out if the freon is under or over pressurized. If you want to check the relay, it's behind the left footwell speaker. It's should be white & is the smallest of the 3 components back there. You can open up the plastic case with some tiny jewelers screwdrivers & look to see if the points are burned. If so, sometimes they can be sanded with a nail file to add some more life to them.<p>gale<br>92 735i<p><br>Would this item cause my compressor to just stop running after a few moments of just turned on? Thanks!<p><br></i><br>

  7. #7
    gale
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    Re: What does the A/C Compressor Clutch Relay do?

    Sounds like there's something else going on with it like Rainman suggested. Could be the A/C system itself is o.k. & it's getting overridden by the DME's or another engine sensor signal, in which case, it's beyond my skill level. Sorry.<p>gale<p><i><br>It is an '89 750iL. And no it does not cycle back on. Only if I turn off the engine and turn it back on. It did this when freon was low and even when I just filled it up. Valves? Crud? I don't know. How would I check? Thanks again!<p><p>What year is yours? Bentley's shows the A/C clutch relay in the fuse box next to the CCM like you say, for 92-94, 88-91 is in the kick panel.<p>If you just filled it, could it be cutting out from over pressurizing? If you leave the A/C on, does the clutch cycle back on by itself after cutting out? Could it have crud in the expansion valve or a faulty expansion valve?<p>I'm not much of an A/C expert. Perhaps ask Fareed or Tom Meacham or others.<p><br>I thought that Clutch Relay was next to the CCM and LKM? Atleast according to a labeled picture that I obtained. BTW, just filled the freon. Thx<p><br>Not necessarily. It could also be cutting out if the freon is under or over pressurized. If you want to check the relay, it's behind the left footwell speaker. It's should be white & is the smallest of the 3 components back there. You can open up the plastic case with some tiny jewelers screwdrivers & look to see if the points are burned. If so, sometimes they can be sanded with a nail file to add some more life to them.<p>gale<br>92 735i<p><br>Would this item cause my compressor to just stop running after a few moments of just turned on? Thanks!<p><br></i><br>

  8. #8
    Rainman
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    If you have checked out the belt and everything

    <center><img src="http://community.webshots.com/storage/1/v1/2/81/89/28428189GSTVZqRXSw_ph.jpg"></center><p>

  9. #9
    Whiskers
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    Re: What does the A/C Compressor Clutch Relay do?

    Thanks again, Rainman and Gale<br>

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