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2005 Nissan Compresor wont shut off Forums > > 2005 Nissan Compresor wont shut off 2005 Nissan Compresor wont shut off
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Frontier Nissan Frontier/HB/Truck Discussion Forum

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  #1  
Old 02-23-2008, 11:10 AM
Trevorg8
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Default 2005 Nissan Compresor wont shut off

I have seen a few posts about the AC not shutting off and always running.

I noticed this recently after 20K miles, the AC controls will be off and yet i can hear the AC comp clickin on and off. When i just run the air and turn of "ac" on the panel inside the comp still goes on and off.
Whats the deal, is this design?
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  #2  
Old 02-23-2008, 06:11 PM
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mpe235 mpe235 is offline
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If you have the air discharge on any position that causes air to come out of the floor or defroster vents it is normal for the compressor to run.
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  #3  
Old 02-24-2008, 08:06 AM
Trevorg8
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I dont understand why they would have an A/C button there, i like to use the air from out side without the compressor kicking on and off. Saves gas too and robs power when on.
I dont get the idea behind the design..

So, even if the A/C button is off and i want the air from out side the compressor will ALWAYS be on?
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  #4  
Old 02-24-2008, 08:15 AM
Trevorg8
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Also, it runs not matter what, in defrost, floor or regular air vents, it runs and runs.
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  #5  
Old 12-11-2010, 12:13 PM
kauaiguy kauaiguy is offline
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1984 300ZX
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I'm new to this site/forum and joined because I just bought a 2003 frontier crewcab from a private party. I noticed (after I bought it) the ac compressor would cycle on/off regardless of where the fan or slector knob is positioned. I mean it does this even if the fan switch is set to zero, the AC switch is off and the selector knob is not in any defrost postion. The compressor stays mostly on (minutes at a time) and will cycle off for just 5 to 20 seconds, and then back on again. When the compressor is running, the air coming into the cabin is really cold so it's not a case where the system needs to be charged, and even if it did, that still wouldn't explain why the compressor turns on at all with all the controls in the position that I described.

I have learned from reading about how the AC system works on these vehicles that once you select any of the two defrost positions, the AC compressor will still stay on even if you select a non defrost position later until the fan or the ignition is turned off. That's not the case here. Again, the fan is off, the selector is not in defrost positions and the AC witch is off.

Before I go chasing through the AC electrical schematics to see where the AC compressor clutch signal is being generated to cause this, I was hoping someone has experienced this as well and has a handle on it.

Thanks
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  #6  
Old 12-16-2010, 02:05 AM
kauaiguy kauaiguy is offline
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1984 300ZX
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Background: This problem involved the AC Comporessor clutch energizing even when the fan switch was off. It stayed mostly on and would click of intermittently, again with the fan switch off. I had discovered that the AC clutch was being energized by the AC relay and the signal to energize the relay was coming from pin 12 of the ECM. The signal to energize pin 12 was coming in on pin 21 of the ECM from pin 2 of the Air Control Unit.

I did remove the Air Control Unit this afternoon and reinstalled it outside of the dash cavity to test it. Much to my surprise, it started working as it was supposed to, i.e. the AC clutch would now only energize if both the AC button was depressed and the fan was swtiched to a non "0" (active)position, or the AC buttion was off, the fan in an active position, and the mode selector in one of the defrost settings. I put everything back together and it still worked OK. I drove the truck several miles and the original symptom never came back! I don't believe in magic, so the only thing I could think of is one of the control wires in the harness in the dash cavity might have been pinched to ground and my removing the radio and air control unit, displaced the harness and removed the short. I'll add another post if the symptom comes back
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  #7  
Old 03-21-2011, 08:55 AM
jackicks
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Default AC Compressor Always Cycling

Hey kauaiguy.

I'm very new to this forum posting business so bare with me. I have the same problem with my 2003 frontier. No matter what position the knobs are in I continue to hear the AC compressor cycling. In one of my Diesel Technology classes at school we had a brief AC section and that's when it became apparent that I may have a problem too.

You said you changed the air control unit? Where is this located exactly? Is it the series of switches in the cab or is it located under the hood?

Thank you!
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  #8  
Old 03-21-2011, 08:11 PM
kauaiguy kauaiguy is offline
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1984 300ZX
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Join Date: Dec 2010
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Aloha Jackicks - The problem did return the very next day (no such thing as magic), but I got real busy and never placed a follow up post (my bad). However, I'm pretty sure I isloated the problem.

Using the service manual I download from this site for this vehicle (for free-great benefit), I chased the signals in and out the Air Control Unit (ACU) and discovered that the the electrical board in this unit is randomly and erroneously sending a signal to the AC compressor soleniod to engage. By the way, the (ACU) is the HVAC unit located right in upper the middle of your dash with the blower control switch, the temperature control knob and the mode control knob, plus other control buttons. I know a new replacement is going to be pricy so I spliced in a toggle switch on the control wire from the ACU that was carrying the signal to engage the AC solenoid. So now the AC compressor won't turn on until I toggle that switch and it turn off immediately when toggled back. I did this as a tempory but effective fix while waiting for an air Control unit to show up at my local wrecking yard.

It's been a while since I initiated this fix and I didn't document at the time (I should have) so this is from memory. Disconnect the battery. You need to remove the center console and the plastic trim that surrounds your HVAC controls (ACU) and radio. I did find a great procedure with photos on this site from someone who shows how to remove these panels but don't recall where. Except for some screws, they're mainly held in with interlocking tabs that release when you tug or pry on them. The radio, but excerise care they are made of plastic.

With these panels off, remove your radio assy. and partially remove the ACU enough so that you can unplug the black 12 pin connector (M95) that plugs into the back of your ACU. Pin #2 on this connector is a blue/yellow (L/Y) wire that carries the signal (normall or erroneously) from the ACU to engage the AC solenoid. It actually take an indirect route by first going through the refrigerant pressure senor, and then into pin #21 of the vehicle's Ectronic Control Module (ECM). An active signal into pin #21 of the ECM causes pin 12 to be active which energizes the AC Relay which in turn energizes the AC soleniod, turning the compressor turns on.

For the fix, I cut the L/Y wire (about a foot from the connector) coming from pin #2 of the ACU's black 12 pin connector and wired my on/off toggle switch in between. There were two unused holes in the plastic panel for ACU and I used one of them to mount my toggle switch. I've attached two jpg files that show the schematics of the ACU and ECM and a photo of where my toggle switch in mounted.

Hope that helps.
Attached Thumbnails
2005 Nissan Compresor wont shut off-ac-acu-jpg   2005 Nissan Compresor wont shut off-ac-ecm-jpg   2005 Nissan Compresor wont shut off-0321111658-jpg  
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  #9  
Old 12-14-2019, 09:31 PM
Robert G 101 Robert G 101 is offline
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2005 Pathfinder
 
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Hi, thank you for outlining the work you did to "fix" what Nissan should have gotten correct the first time, I always hear my A/C compressor on, I can't stand the fact that I am losing fuel to something I do not need on all the time, when my Pathfinder was still under warranty I brought it in for this reason and I was told it was fixed, well it still doesn't shut off, I am going to have to add a switch to cut the power as you did, for shits and giggles my friend had a Cadillac that I ran a 110 volt light switch inline to turn on and off the compressor until he could get the a/c pressure switch fixed, it worked and now 24 years later I am looking at a similar reversed scenario that I have to stop power to my a/c compressor, Thanks again for your post, it's helped me considerably, Peace :}
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