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Discussion Starter · #1 · (Edited)
SUCCESS!!!!!! Cold A/C again!!!!! All it turned out to be was a broken wire on the refrigerant pressure sensor harness connector!!!!!!!

Everything can be reached (barely) without removing the bumper cover in your 2013 to 2015 Altima just by removing a couple of pieces of plastic above the sensor and disconnecting the horn wiring to pull the harness connector wiring (and not the connector plug itself) through the support fixture from the bumper side to the engine side so you have adequate space to install the new harness connector .

You could remove the bumper cover and replace the sensor harness plug without the cover in the way however you still might need to pull the wire through the support fixture anyway as there's not much slack in the wiring to work with where the harness plug connects to the sensor and goes into the support fixture hole.

The new wire harness connector plug and the solderless no wire-stripping low voltage wire connectors were from Bezosmart and only cost $21 and I got some help from a local mechanic who paid it forward and checked the voltage on that sensor with his scan tool for free and told me it read 0 volts. Thanks very much Trevor!

I will provide links for the replacement sensor harness plug and the wire connectors with my last (probably) posting at the end of the thread.




Well friends, it was too good to be true and the automotive gremlins have just had their say just beyond 100K miles
with my 2014 2.5S with the manual A/C. Just a couple of weeks ago I had said I had no problems with my Altima - nice while it lasted.

The compressor clutch engages during the IPDM auto active test. Fuses are good. Should have enough refrigerant in it since the static pressure is 90 psi.
There are still many things to check which are preventing the relay from grounding the compressor clutch when the A/C button is on.

Might have to go to a Nissan stealership to have it diagnosed as I thought the compressor clutch was the most likely issue
given that there should be more than enough refrigerant in the system for the refrigerant pressure sensor to allow the compressor to start.
But the clutch was engaging perfectly during the self test so the clutch or the wiring isn't the problem.

Luckily this didn't occur next month or in July. But I do need to get this fixed before then.
Covid-19 has created a large backlog of repairs at mechanic's shops near me. Wanted to have the same shop
that fixed the A/C on another of my cars but they did not even bother to diagnose it when I brought it in with an appointment I
made six days prior. Their excuse was they had other cars to repair before the could get to mine. Seems that they are taking on more work than
than can reasonably handle. I won't be going back there again.

There are several knowledgeable people on this forum and some of you might have experienced this with your Gen 5.

I know there's a compressor issue with the automatic air conditioning with the SV and SL models. Not the case here.

I have the service manual and have been trying to understand what to check. The A/C control panel is a possibility but I'm not
going to shoot the parts cannon at it in hopes of fixing it. If I can't stumble upon the cause, off to the stealership I go.
 

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Discussion Starter · #2 ·
I'm suspecting the refrigerant pressure sensor as the root cause for this since a faulty one will not allow the compressor clutch to engage.. But I would've expected (hoped) that there would've been an OBD2 DTC stored in the engine ECM. No DTCs stored. I am going to attempt testing the sensor but the FSM is not very helpful as it makes you jump around from chapter to chapter and within the primary one (HAC). No YouTube vids for how to get at it or replace it that I've found yet which would be most helpful.
 

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Discussion Starter · #3 ·
Well, the refrigerant pressure sensor is easy to get to after removing the bumper cover and a plastic piece above it. It's conveniently at the top of the condenser.
Just checked if the wires were broken on the outside of it - nope.
 

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Discussion Starter · #4 · (Edited)
Would need to be ABSOLUTELY certain that the refrigerant pressure sensor went bad because Nissan cheapened out and did not include a Schrader valve so that the switch could be replaced without needing to remove the refrigerant from the system. Not the end of the world but still come on Nissan! Could be a wiring problem to or from the sensor. Makes me wonder if the IPDM auto active test for the compressor clutch includes the signal from the refrigerant pressure sensor or not. I'm leaning toward not.

Just learned that the refrigerant pressure sensor is tested at the ECM next to the 12V battery. Need to have the ability to connect a voltmeter to the terminals with the engine running which requires diagnostic equipment I don't own and wouldn't buy just for this issue. Going to a Nissan stealership makes the most sense here because they have CONSULT.

Back to the start.

The A/C is not turning on - 12V is not being supplied to the compressor clutch to engage it and run the compressor when the A/C switch is turned on in the cabin
There is adequate static pressure in the system.

Here's what the FSM says to do.

1.CHECK MAGNET CLUTCH OPERATION - Yes, it operates normally during the IPDM auto active test
2.CHECK REFRIGERANT PRESSURE SENSOR - Don't know if it's failed and not sure I can test it.
3.CHECK FRONT AIR CONTROL OUTPUT SIGNAL - Nissan CONSULT verifies function is good.
4.CHECK ECM INPUT SIGNAL - Nissan CONSULT verifies function is good.
5.CHECK IPDM E/R INPUT SIGNAL - Nissan CONSULT verifies function is good.

If to this point all of the above have checked out as good....
Check CAN communication system. Refer to LAN-18, "Trouble Diagnosis Flow Chart".

Bottom line....One of the four items below the first in the list SHOULD be preventing the compressor from starting
but if none of them are tracking down the problem could be very difficult.
 

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Discussion Starter · #5 · (Edited)
Found a website with an A/C issue similar to mine for a 2010 Nissan Sentra B16. The page was useful in that it had screenshots of what can be checked and monitored with the Consult 3 Plus software which makes tracking down the root cause of failure easier. Wish I had access to this software but I could ask the stealership to check the ECM operating PIDs when they scan my car. That way if it is the refrigerant pressure sensor (or associated stuff) that's faulty, its erroneous voltage reading (too high or too low) will be obvious and turn out to be the component (ECM, sensor, or wiring) which must be replaced or repaired.

 

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Discussion Starter · #6 · (Edited)
It appears that I can check the output voltage of the three wire refrigerant pressure sensor at the sensor itself if I add jumper wires between the sensor and harness so that the sensor remains connected to the ECM. This is easy enough to do but needing to remove the bumper cover just to find that the sensor output voltage is within range is something I wish I could avoid since Consult 3 Plus reads this voltage as one of the PID inputs needed for it to authorize the IPDM E/R to energize the relay and close the compressor clutch. It's not possible to back probe the harness to read the voltage. I could pierce the wires at the back of the harness to read the voltage but there's not much room to do this without removing a large plastic piece above the harness.

POST REPAIR UPDATE:

TO REPAIR THE AC ALL THAT WAS REQUIRED WAS REPLACING THE HARNESS PLUG YOU SEE BELOW.
THE PROBLEM WAS THE GREEN WIRE WAS BARELY HANGING ON AND WAS NOT CONNECTED TO THE PIN ON THE OPPOSITE SIDE
HENCE WAS READING ZERO VOLTS.

IT SURE LOOKED LIKE THE GREEN WIRE WAS STILL CONNECTED BUT NOPE!
I DIDN'T WANT TO BACK PROBE THE CONNECTOR FROM THE SIDE YOU SEE BELOW AS IT COULD'VE IRREVOCABLY DAMAGED IT.

IT DIDN'T MATTER ANYWAY BECAUSE THE PLUG REQUIRED REPLACEMENT DUE TO WHERE THE GREEN WIRE BROKE OFF WHICH
WAS RIGHT WHERE THE WIRE COMES OUT OF THE PLUG - NO WAY TO FIX THAT EASILY. THE REPLACEMENT HARNESS PLUG WAS
INEXPENSIVE WHICH HELPED.
102092
 

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'But the clutch was engaging perfectly during the self test so the clutch or the wiring isn't the problem.'

Not correct. The clutch may well seem to come on fine but if partially shorted can be weak to not stay on and same if the bearing gets loose to shake the clutch back loose. Compressor can have error that doesn't show up there either like broken reeds to not pressure up.

The electrical has limitations, all it can do is deduce mechanical things in an electrical way, not all of those can be diagnosed with the ECM.

Why you throw on gaugeset and read pressures to get a much faster handle on things.
 

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Discussion Starter · #8 ·
Attaching my manifold gauge set was the first thing I did. The system has pressure and is not leaking. This isn't my first A/C rodeo. I have worked on automotive and home A/C systems a couple of times before this.

I'm going to a mechanic this afternoon who said that he will attempt to read the voltage of the refrigerant pressure sensor with one of his scan tools free of charge (no pun intended). If this voltage is in its normal range then I will have to go to the stealership to have the BCM, IPDM, and Engine PIDS read.. I might not go through with it as I have doubts they will do what I want. They will just claim that nothing is wrong electrically if no DTCs are present and charge me $145 for doing nothing to help.

I doubt the problem is mechanical. There was no noise from the compressor or bearings before; the A/C simply stopped working. The clutch never engages when the car is running because no voltage is sent to it from the IPDM as directed by the ECM when I turn on the A/C. I've already checked that there's 0V at the harness to the clutch when I turn on the A/C switch with the engine running at operating temperature
 

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If you can get to the IPDM wire needed that sends signal you can use a $5 relay wired up to cut on clutch as a test without any of that other work. In fact you can even rig it to be permanent as I did once on a Ford to bypass having to buy an unobtanium CCRM relay module backordered to forever and cost $250+. Car ran for years like that and a/c worked fine. Cost maybe $15 in parts.
 

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Discussion Starter · #10 ·
I thought about doing that but I'd rather keep everything stock. If I put in a way to send battery power to the clutch to engage it at will I would need to switch off the compressor at times to prevent it from running it too long. And there are conditions when you don't want the compressor to run that I would need to remember. Cost isn't really the issue, I can afford it. I just want the repair done right, only once, and not get ripped off. Which is why I do all of the repairs I'm capable of with the tools I have. It would be nice to have the Consult 3 Plus software and there are pirated versions that might work but dang it sometimes you just have to take it to someone with the tools you wished you had.

Just got back from the mechanic I mentioned 12 hours ago. They ran their scan tool on my car (no charge) and said that the refrigerant pressure sensor is reading 0V. If this is valid, then that would explain why the compressor clutch won't engage. There is a possibility that a wire is cut underneath what is on top of it which would also result in a 0V reading at the sensor.

I'm hoping that the mechanic will at least check for a broken or disconnected wire before replacing the sensor. They can't get my car in until late next week at the earliest. Now I'm very tempted to get at the sensor in the meantime to see if they were truthful or lying to me just to get my business. It wouldn't be all that difficult for me to test (once I get to it) and I have over a week to do it sooooooo............

Also, I just cancelled my appointment at the stealership for tomorrow. I can always get the Consult 3 Plus scan done later if this doesn't solve the problem.
 

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When I did the a/c relay box override I did it in such a way that the computer still controlled everything, I didn't have to turn compressor off or anything like that. It was transparent and same operation as OEM. I DID have to sort through about 40 wires to find the right 2 though.

Speaking of such OEM is fine until it's costing a bundle and then I jump ship to do my own work. I don't hesitate to switch to parts that never came on the cars if they fix something to save big money. I've fixed badly slipping ATX with a thirty cent washer in a strategic location to instantly go back to working fine for 20 more years, in a trans that had to 'have a new one' according to the shops that did the estimates on it. Instant $2500 for removing a snap ring, cover and doing the switch.

Wire cut or other is possible on the a/c pressure sensor there but more likely the inside semiconductor just failed. I'd love to have Consult as well but there so far have been ways around it, just like with the Fords I ran for 30 plus years.
 

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Discussion Starter · #12 · (Edited)
It's looking like it's not a problem with the refrigerant pressure sensor itself after all. I was able to disconnect the harness from the sensor without removing the bumper cover and checked if there was 5V reference voltage coming from the ECM to the harness - nope, no voltage at all on the green wire (#1 on E219).

However, there is 5V in the green reference wire (pin 83) at the IPDM connector E201 when I back probed it so I most likely have a broken wire somewhere near the sensor as there was no continuity between IPDM E201 pin 83 and the sensor harness pin 1. Finding and repairing the break in the wire is going to be a challenge as there's not much room to work and the wires go through a hole in the supporting fixture that the condenser, radiator, and fans mount to before reaching the sensor.
102112
102113
 

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Discussion Starter · #13 · (Edited)
Just ordered a new harness connector and some three way T-Tap wire connectors from Bezosmart. I'm going to route the new three wires through the opening in the supporting fixture and crimp to the wires on the engine side of the fixture. I will be able to determine if the 5V signal reaches the green wire in the bundle on the engine side by crimping on the T-Tap onto the existing wires.
102117

I'm not certain if the new harness connector is a match to the existing one but if not I can return it.

Just checked if there was continuity for the other two wires #2 white and #3 red. They both had continuity to pins 82 and 86 respectively in the IPDM so I suppose I might just need to crimp in a new wire for the 5V green reference and keep the existing sensor harness connector. That's assuming the wire going into the harness on the bumper side of the fixture isn't where the open is - it doesn't appear so. It's difficult to understand why it's only that green wire and not all three.

Oh well, if that takes care of it I'll be happy as it will have cost me only $20 to repair not including the many hours studying the wire diagrams and connectors (and writing these posts for you and me). This might happen to someone else's Altima as it seems that Nissan used the minimum amount of wire to reach this sensor. Every penny counts in a vehicle with thousands of parts. And happened it has. Another seller of the same harness connector plug sold one to a 2013 Altima owner. Small world.
 

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Discussion Starter · #14 · (Edited)
Okay, the green wire was open on the opposite side of the harness connector so I am going to need to install the new harness plug pigtail. The green wire broke off what little of it was still holding it on to the harness plug as I was cutting away some of the black plastic sheathing around the three wires so I could attach the wire connectors for the new harness plug pigtail. Nissan did not add any slack to the wires and the green wire eventually broke by being bent 90° from the harness connector and had been pulled away from it while driving. I hope that the new harness plug will match so I can repair it today. I need to be extra patient though and do it correctly. I disconnected the horn wiring to pull out the harnesses to have adequate space to attach the new harness - whew! You cannot remove the sensor wiring from the support fixture without disconnecting the horn wiring because they are joined inside the support fixture itself. Thanks again Nissan - NOT!

SUCCESS!!!!!

Amazon delivered the two parts I required in one day (wifey is a Prime member). Took me about an hour to install the new harness plug for the sensor. Started the Altima and pressed the A/C button and heard the oh so sweet click of the compressor clutch engaging, yessssss!!!!! Immediate cooling on a cool late spring day (only 70°F in SE Michigan today).

Here are two links - one for the replacement harness plug ($8.99 plus tax and shipping if you don't have Prime) and one for the wire connectors $10.95 plus tax. These two items are guaranteed to work on your 2013 to 2015 Altima if you are unfortunate enough to have this happen to you. The three wires for the sensor are 24 AWG so you will need to buy a shrink type connector or one like I used here. The new harness plug wires are thicker 20 or 22 AWG but still fit into the wire connectors. Be sure to put the new wires into the long end of the tee and the existing wires into the top of the tee. Also the colors on the new harness plug are different but as long as you match the new harness plug to the original plug (sky blue to green, white to white, and green to red you'll be in like Flint (1967 film starring James Coburn).

Not sure if anything changed with the refreshed bodywork in 2016 so this A/C repair might not be your oyster as I have no clue if you will be able to reach the sensor without removing the bumper cover which I was so pleased I did not need to do.

Final thought - I'm so damn glad this is all over. I'm getting too old for this s***. The time will come when I'll have to pay the man to do a simple job like this. Sigh.

Amazon.com: ALLMOST New AC Pressure Switch Sensor Connector Plug Pigtail For Nissan Infiniti Mazda Mitsubishi: Automotive

Here's the same sensor plug for only $6 shipped. But you might have to wait a while to get it as it might be coming from China.
Crankshaft Position Sensor Connector Pigtail Plug For Nissan Infiniti 23731-4M50 | eBay

Low Voltage Wire Connectors, Solderless No Wire Stripping 3 Way 1 Pin Small Gauge Wire Connectors, Easy Connection T Tap Connectors, Fits 24-20 Gauge Wires, 16 Pack - - Amazon.com
 

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I'm glad you were able to fix your a/c problem. Kudos to you for sticking with it.
 

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I would have run a single wire in a custom location so easier to get to most of it if the problem shows back up. The wire gauge there is too small and maybe why problems, I would use no less than 18 as the clutch needs a lot of amp and thicker wire is harder to break completely from vibration.. A fix there for likely under $10. I use pin connectors from Digitech at maybe 25 cents each and commonly reuse the same plastic protective housing. A LOT of modern car wiring issues are now from them shrinking the wire gauge too small for weight and cost lowering. Common for harnesses to be getting almost too short too. I can think of at least 10 Ford Focus issues caused by the same.

Just watched both movies, Flint 1 and Flint 2. Ever seen the 'President's Analyst'? Where the evil world wide takeover is from the PHONE company?

Yours of course and do as you will. Luck with the fix.
 

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This was exactly the issue I had with my AC a couple of years ago. I had to replace the pressure sensor harness as one of the wires was corroded and disconnected. It seems like a more common issue than it should be. I'm glad you found the problem and a MUCH cheaper fix!
 
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