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Ac doesn't work

157 Views 5 Replies 2 Participants Last post by  VStar650CL
2006 Nissan murono, had a hole in ac hose, took it to a shop where they replaced the hose and charged it back up with a machine and now the ac won't come on any suggestions would be great. Thanks
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Your Murano is like most Nissans with Auto A/C, there's a chain of devices involved in turning the A/C on. The Auto Amp gets button and setting signals from the AC/AV Switch Panel, sends an "A/C on" request to the BCM via the CANbus, the BCM forwards the request to the ECM on CAN, the ECM forwards it to the IPDM on CAN, and the IPDM turns on the compressor. All of the intervening devices can veto the request for various reasons, so unless the problem is a blown compressor fuse or bad clutch, finding out why it won't turn on means finding out who's using their veto power. Start with the basics, is the compressor switching on? If it is, then the compressor is bad or there's a blockage or some other problem in the plumbing. If it isn't, is the fuse good? If it's good, does the connector at the compressor light up a test lamp? If so, the clutch is bad. If not, when you stream the A/C pressure from the ECM, does it read zero? If so, the pressure sensor is bad. Does the ambient temperature on your dashboard read winter temperatures? If so, the BCM will veto turn-on because it thinks you're in Alaska. Do you hear a click from the IPDM when an assistant turns the A/C button on and off? If not, the compressor relay inside the IPDM may be shot.

From there it gets more complicated, because most DIY scanners can't read the BCM, IPDM, or Auto Amp. One of those will be exercising a veto, so you might need a dealer scan of those devices plus the in-car and intake (evap) temperature sensors to pinpoint where the problem is.
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Well the shop informed me that they can apply juice to the compressor and it works fine and gets cold, one thing i didn't check was the temperature on the dash,can't believe that it would effect the the ac,wow,very informed, now it's at the same place that just replaced and programed the ecm,could he have forgotten to add the ac system?
No, the ECM programming won't affect that, the only part it plays in A/C is monitoring the pressure and cutting the compressor at WOT for extra power or to reduce load if the engine overheats. That would be the same regardless of model or variants. Like I said, a dead A/C Pressure Sensor will kill it because the ECM will think there's no refrigerant, and there are two other temperature sensors which can also kill it, one in the cabin and another on the A/C evap. If either one of those goes open-circuit it will read "Alaska" and the Auto Amp will refuse to turn the compressor on.
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Appreciate the help VStar👍
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