AC compressor has no power

2003 MERCEDES BENZ SL500
109,507 MILES • 5.0L • V8 • RWD • AUTOMATIC
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JAMIE LOPEZ
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Vehicle has a new AC compressor, pressure/temperature switch, is full of crown (2.09lbs), but still has no power to compressor. Check all fuses under hood, all okay. Checked wires from switch to connector m15, all okay, but no 5 volts reference or no .8v to 1.8v on the other three wires. I cannot find any kind of wiring diagram for this car, AC or other wise. Please help me figure out this nightmare. thanks in advance.
Oct 18, 2016 at 2:03 PM
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WRENCHTECH
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Have you checked and cleared the codes in the HVAC module? If there are any stored codes from the original failure they will inhibit the compressor until cleared.
Oct 18, 2016 at 3:36 PM
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JAMIE LOPEZ
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Yes, all codes are cleared, still no power at compressor.
Oct 18, 2016 at 4:01 PM
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WRENCHTECH
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I am not talking about engine codes. I am talking about codes specifically in the HVAC module that can only be access with a very high grade scan tool. If it is resetting any codes, then follow up on that. Other than that it going to be following a wiring diagram by an electrical technician.
Oct 18, 2016 at 5:03 PM
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JAMIE LOPEZ
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I have a high grade scan tool, a Matco Maximus 2.0A, so yes all codes are clear! I have already check the wiring from the left Sam module to the switch and to the compressor, but for some reason I cannot find and electrical diagrams for this car. Do you know of a website that I can access to get these? As you know that tracing done a electrical problem with a diagram is almost impossible.
Oct 18, 2016 at 6:50 PM
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WRENCHTECH
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I do not know if you have ever tried to follow Mercedes diagrams, but it is not easy. http://i1198.photobucket.com/albums/aa448/Wrenchtech/176294525.jpg http://i1198.photobucket.com/albums/aa448/Wrenchtech/176294526.jpg http://i1198.photobucket.com/albums/aa448/Wrenchtech/176294527.jpg http://i1198.photobucket.com/albums/aa448/Wrenchtech/176294528.jpg http://i1198.photobucket.com/albums/aa448/Wrenchtech/176294529.jpg http://i1198.photobucket.com/albums/aa448/Wrenchtech/176294530.gif https://www.2carpros.com/images/external/176294531.gif
Oct 18, 2016 at 7:01 PM
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JAMIE LOPEZ
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Yes I have and you are right they are very hard to follow, but these diagrams are what I have been looking for! Thanks so much! I will let you know what I find. By the way you wouldn't have any idea or guess at what it might be?
Oct 18, 2016 at 7:28 PM
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WRENCHTECH
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Pressure switches and relays are the most common areas of failure.
Oct 19, 2016 at 2:33 AM
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JAMIE LOPEZ
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Can you possibly post a picture where the AC fuses and relays are? Thanks in advance
Oct 19, 2016 at 7:43 AM
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JAMIE LOPEZ
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In relation to where they sit in the fuse block..
Oct 19, 2016 at 7:47 AM
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WRENCHTECH
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It is less work to just test all of them then research which ones are which and location.
Oct 19, 2016 at 7:58 AM
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JAMIE LOPEZ
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Okay, thanks.
Oct 19, 2016 at 8:32 AM
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JAMIE LOPEZ
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Ok, I've check all fuse and relays, all are good, checked power and ground at the acc module, all good, checked for signal coming out of acc when ac power button is push, signal is good, could it possibly be the left sam/fuse block??
Oct 21, 2016 at 7:46 AM
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WRENCHTECH
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That's what the wiring diagram is for. You need to print that all out, tape all the sections together and mark all the components. I can't tell you much more about the circuit. If you have a high grade scan tool you can read each SAM and see what is going on.
Oct 21, 2016 at 8:59 AM