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It’s been a while since provided an update.

Last thing they changed was the a/c compressor 1 month ago and i can confirm that finally fixed the erratic air flow pressure.... i haven’t had any issues since and it’s been a month... air flows speed turns low/high to my setting. Took about 1.5 mths for them to correct the issue but at last it’s fully functional as it should. So if any of you’s are having this issue run this by your mechanic and hopefully that will resolve your issue as well....

However, there is another, i don’t want to say issue but something I’ve notice that hopefully you’s can confirm if this is normal or not. My heating temperature will stay almost at same hot temperature from 62 to what ever the highest temperature is. Meaning from this temperature and above my heat comes on pretty humid and it don’t really feel a change much. So temp at 68 which i feel should be a warm/cool breeze feels like temp at 88. I just keep the air flow low so it won’t get too hot. The only time it will drastically change is if i go to 61 or 60 which is the lowest. Then cool air will come on.... this is not normal right? If i should want a cool fan like breeze coming in should that be around the mid 60s? Now through all this i am not in AC mode cuz i am not looking for cold frigid air flow.....

Can you’s let me know how your temperature feels at 62-70?

Thanks
 

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Hi folks. I'm new to the forum. We are having an issue with erratic blower air volume output on our 2015 Pathfinder SV. On initially starting, HVAC system works normally in both a/c and heating modes. After a period of time from minutes to hours, air volume output from all vents will quickly reduce to almost nothing with no real change in blower motor sound. Reduced air flow affects aĺl vent modes, recirc and fresh air, as well as dual and single modes. Blower appears to run appropriate to blower setting, just no airflow from vents. Output from rear passenger system similarly affected. Nissan mechanic has spent hours trying to diagnose. Cabin filter replaced, intakes checked for obstructions and blower motor removed and checked. Malfuntion will continue until car is turned off and allowed to sit for a long period. (Of note, issue first appeared some weeks after repair work completed for large stone impact to underside which caused significant damage to frame, oil pan, a/c leak, drive train etc.) Does anyone have any idea what could be causing this?
I'm having the exact same issue! It usually works when i start the car and will be fine for short trips but then stops blowing cold or warm air out of vents. I can hear the fan blowing but the sir dorrs are short circuiting for some reason. I brought to mechanic and of course it worked fine for him so we are at a loss. Good think I have heated seats because its gets pretty chilly in MN
 

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I wish we had some resolution to this but it hasn't happened yet best I can tell!

Seems odd to me too because any decent shop will have data scanners that will tell you positions of the HVAC blend doors and display any HVAC system codes, unless for some odd reason Nissans don't do this.
 

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I'm having the exact same issue! It usually works when i start the car and will be fine for short trips but then stops blowing cold or warm air out of vents. I can hear the fan blowing but the sir dorrs are short circuiting for some reason. I brought to mechanic and of course it worked fine for him so we are at a loss. Good think I have heated seats because its gets pretty chilly in MN
I am having the same issue with a 2015 as well, hoping someone here smarter than me gives some advice!
 

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I am having the same issue with a 2015 as well, hoping someone here smarter than me gives some advice!
This happened to me. The compressor in these vehicles has a variable valve. The mechanics swapping out these compressors have to be 100% certain is the same compressor. After I replaced my compressor, it was freezing and no air was coming out of the vents.. Later, I found out they sold me the wrong compressor model.

Sent from my SM-G970U using Tapatalk
 

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Hi folks. Here is an update to my situation that started this whole post. After a number of trips to the dealership and additional troubleshooting on my own i have established that the airflow blockage is being caused by the AC evaporator coil freezing up and completely blocking the airflow through the airbox. For some unknown reason the AC compressor is turning on sporadically when in heating mode and does not turn off. This causing the ice-up. I can correct this by pulling "a/c con" fuse. Within a few minutes the ice melts and airflow returns to normal. Looking back now to this past summer I now realize this was happening occasionally in the heat of summer too. The issue now is to determine why the ac is sporadically turning on and why it continues until the evaporator is completely blocked with ice. Hope this information helps some of you having similar issues. If you want to check, look at your compressor. The lines will all be frosted up and the compressor will be running even though you did not select it on. I will update when I have more info and hopefully have this repaired.
OK silly question, but where is this "a/c con" fuse you speak of? Ive checked the cabin fuse box and the 3 under hood boxes with no luck. I am having this exact same issue and now that winter is rolling in i need a temp fix at least to have consistent heat. thank you very much for your help
 

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I recently resolved this issue at the shop I work at, and let me tell you, it was by pure luck. No amount of skills would have done it, so take it easy on them. This one was in a shop out of state, and several times at mine before I got it and had it for a week.

Customer said they would hear the fan blowing but nothing coming out of any vents on any setting. They came in on a Saturday and I couldn't reproduce the complaint. Brought it back again, I could reproduce the complaint (this happens allllll the time by the way). That time I asked if I could keep it and drive it home, which is 50 miles round trip. On my way home I had our scan tool hooked up and monitored the outside temp, in car temp, coolant temp, ac pressure sensor, ac compressor request signal, ac relay signal, and evaporator core temp. The problem occurred the entire cold ride home.

I saw the evaporator temp dropping, at one point to -6*f, and the ac compressor being commanded to stay on. It's supposed to shut off under around 40* to keep the evaporator from freezing. The evap is one of the first parts in the duct path and if it accumulates ice, it will block the flow through the vents.

After doing some research in the service manual about the system, I saw that anytime you push the auto temp button, it should also illuminate the ac button, which this one wasn't. The ac compressor would be commanded on, unless I pushed the ac button to illuminate it, then push it again to turn it off. I could do this to get the compressor to turn off, and close the intake door by pressing the recirculate button to warm up the evaporator again.

There is a mode door test that tests all of the doors and they all moved, but nothing would blow out, except for the 3rd row seat, which is all different and makes sense that it would still work.

The ac auto amp gets signals from the buttons, processes the combinations and sends the ECM a request to turn on the compressor clutch. The ECM looks at other data like the ambient temp, evaporator core temp, rpm, sun load sensor, to determine if it can turn the clutch on, and if it can, it sends power to the IPDM, which then powers up the clutch.

All of the data points to the ac auto amp being the problem by telling the other parts to turn on the compressor when it shouldn't be on. The problem is that we had already replaced the amp...there was a 2014 Pathfinder at the shop and I monitored the same data on a test drive. This one illuminated the ac button with the auto temp on and also cycled the compressor anytime the evaporator core got to about 35*. Nice. So I pulled that amp out and put it in my problem car, and it fixed it. Funny thing is, the part is different. It's for 2013-2014, and mine was a 2015, with a different part number. Parts manager spent some time looking into it and it appears that the part I just put in it that fixed it is the "wrong" part. So, to make sure I didn't just get a bum new part we ordered another amp, that is supposed to be correct in this car based on the vin. It didn't work. I put the 2014 part back in it, and it works...

Some Nissan's use a variable rate compressor that changes the piston stroke based on need instead of cycling on and off, but those compressors have two connectors, one for the clutch and a separate one for the pulse width modulation. 2014 and 2015 didn't have that.

I'm not sure how this could suddenly happen, but seemingly only to 2015s. I can't help but to think there is something wrong with the parts catalogue where that new part change over happened and the build date change there. Or some other part gets changed that doesn't jive with the ac auto apt in the car, but does with the 2014. I saw a painter black aftermarket compressor in the car, and wondered if it was the wrong one, but I don't think the compressor would impact the amp command signal. I don't know what was going on there, but anyone having this problem, I would get a cheap scantool that can show those values and see if the same is happening. If it is I'd try a 2013-2014 ac auto amp from a junk yard and see if it fixes it. Just make sure the part number is different from the 2015, because the change happened mid year in 2014. They are like $200 new.

I had the car for a week, which sucks for the customer, but that's how this stuff goes. You look at them a little each day since there is other work to get done, and we only make money when work is getting done.

Maybe this will help someone out at some point.
 

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Thanks for sharing and the detailed write up.
Can you please let us know what is the "auto amp", where is it located and the two PN's.
This would be very helpful for others to fix the issue.
 

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Thanks for sharing and the detailed write up.
Can you please let us know what is the "auto amp", where is it located and the two PN's.
This would be very helpful for others to fix the issue.
You're welcome. The ac auto amp is basically the brains of the ac system. It takes inputs from the buttons and sensors and processes the data to perform outputs like moving mode and blend doors, vary blower motor fan speed, or try to get the ac compressor to turn on and off in this case. It looks like the parts catalog calls it the HVAC control module. The part number for the one that was not working in this 2015 was 27760-9PB0A and the one that fixed it was 27760-3KA3A.

The part is mounted directly under the radio unit, not the display. The dash is weird on these. There are displays for the radio and hvac, but the actual units are behind them separately. They are not hard to replace. I believe the book time is 1.4 hours. You just need a tool to pop off the trim pieces that you can get from harbor freight, a Philips screwdriver, and (I believe) a t25 torx bit. I might be wrong about that bit size. There is a thin flat trim piece on the bottom of the main display screen that pops off to reveal a screw. Take that out, then you can pop off that display section. Then there are four more screws in there that come out with a bracket looking thing. I know, pictures would be better here, but it's straight forward once you feel comfortable ripping these pieces out. You feel like you're going to break them at first. Then I believe there are two more screws holding the lower panel in place, then two others at the bottom of the center section bracket that holds the radio unit where you can see that cds would slide into. The white plastic rectangle under the radio unit is the ac auto amp. Take off one of the side radio brackets then just take out the one rear torx bit in the other side, disconnect harnesses on the back and replace it. There is no programming or anything, it just goes right in.

I'll add that this is not a guaranteed fix for anyone's specific vehicle and that your should look at the data with a scantool to see if it is even possibly the reason for your problem. I am a big advocate for people doing their own repairs, but also advocate for diagnosing the problem the best you can. "I had this problem, try changing this part" can get expensive! This is also NOT what professional technicians do to find the problems, and of course everyone makes mistakes, which the customer shouldn't be paying for anyway, unless it really was part of the problem. Unfortunately there are a lot of shops who don't do much in terms of training and of course some people just suck. There are a lot of professional level diagnostic trainings out there for anyone serious about learning the basics and beyond.
 

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They gave me model # DKS17D
My model # DCS171-C

Hopes this helps

Sent from my SM-G970U using Tapatalk
This turned out to be the exact issue- compressor was replaced incorrectly. It was replaced with the correct part number this last week and appears to be working fine. Thanks all, the dealer had no idea until I pointed this out!
 

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You're welcome. The ac auto amp is basically the brains of the ac system. It takes inputs from the buttons and sensors and processes the data to perform outputs like moving mode and blend doors, vary blower motor fan speed, or try to get the ac compressor to turn on and off in this case. It looks like the parts catalog calls it the HVAC control module. The part number for the one that was not working in this 2015 was 27760-9PB0A and the one that fixed it was 27760-3KA3A.

The part is mounted directly under the radio unit, not the display. The dash is weird on these. There are displays for the radio and hvac, but the actual units are behind them separately. They are not hard to replace. I believe the book time is 1.4 hours. You just need a tool to pop off the trim pieces that you can get from harbor freight, a Philips screwdriver, and (I believe) a t25 torx bit. I might be wrong about that bit size. There is a thin flat trim piece on the bottom of the main display screen that pops off to reveal a screw. Take that out, then you can pop off that display section. Then there are four more screws in there that come out with a bracket looking thing. I know, pictures would be better here, but it's straight forward once you feel comfortable ripping these pieces out. You feel like you're going to break them at first. Then I believe there are two more screws holding the lower panel in place, then two others at the bottom of the center section bracket that holds the radio unit where you can see that cds would slide into. The white plastic rectangle under the radio unit is the ac auto amp. Take off one of the side radio brackets then just take out the one rear torx bit in the other side, disconnect harnesses on the back and replace it. There is no programming or anything, it just goes right in.

I'll add that this is not a guaranteed fix for anyone's specific vehicle and that your should look at the data with a scantool to see if it is even possibly the reason for your problem. I am a big advocate for people doing their own repairs, but also advocate for diagnosing the problem the best you can. "I had this problem, try changing this part" can get expensive! This is also NOT what professional technicians do to find the problems, and of course everyone makes mistakes, which the customer shouldn't be paying for anyway, unless it really was part of the problem. Unfortunately there are a lot of shops who don't do much in terms of training and of course some people just suck. There are a lot of professional level diagnostic trainings out there for anyone serious about learning the basics and beyond.
I wanted to thank you for this thread, and more importantly, this particular post. I have been trying to find a solution to our 2015 Nissan Pathfinder "low air vent flow" problem for over a year now and every time we'd take it into the shop, same thing, they'd say, "it's working perfectly." I kept telling them "You have to take it on a drive down the freeway for 10-15 mins, then you'll notice the airflow via the door blenders will shut off. As I read this thread, it was as though I was reading every single thing I've done as well. To no avail....until I ordered the HVAC Control Module part# 27760-3KA3A on ebay for 23 bucks, took the front panel off (easy peasy...no problem at all) and SHAZAAM!!!! Halleluiah!!!! Glory to God!!!! IT WORKS!!! Even the Nissan "certified" mechanics couldn't find the problem or fix it. I fixed it for 23 bucks and about 10 mins labor time with this video.
Thank you thank you thank you! But I won't buy another Nissan unfortunately. Quality control is not good at all.
 

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That is pretty sweet that it's a plug-n-play fix. No programming required. This thread is going to save people from major headaches and wasting a ton of cash. I think we've got several threads floating around where techs have thrown thousands of dollars worth of parts and services at 2013+ PFs for this issue and never addressed this particular control module.

I'm assuming since the problem is sporadic, maybe this module needs to get to a specific temperature where things expand/contract for it to act up?

Like Tutti said above, I don't know how'd you be able to test / troubleshoot / diagnose it right down to this module other than by luck given some features it controls work while others don't and the problem moves all over the place.
 

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Yeah, there is no way to know. You would order one for the car, and it would be not work. It's hard to say after replacing a part with a new part that you got a bad one, even though it sometimes does happen. After replacing two of them, it's really hard to say that. I think that what might be happening is that an AC compressor goes bad and is replaced with the wrong one, then the auto p doesn't work right with it, so you either change the compressor or the amp.

The problem happens when the evaporator freezes, so I think it depends on the conditions, like humidity. I couldn't always get the car I was working on to do it but my theory was to keep keep it outside in the cold then bring it in the warm shop, hoping it would get the metal sweating. Then with the compressor constantly being on I hoped to get it to freeze. The main problem is that the compressor is staying on I believe this has to do with a part being changed and not jiving with another.

Remember, technicians are individuals who work at a location. The "dealer" isn't the specific person working on the car. They have some factory trained technicians there, but that factory training is limited since they can't cover the billion different issues that come up. There are good techs and bad techs at all shops, like every company. This would be very difficult for someone to find a fix for, no matter who they are, how much experience or training they have.
 

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Tutti, I'm totally with you on this, but in regards to those who had the a/c compressor replaced because of this, I still don't understand why. If your high and low side pressures are normal, there's no refrigerant leaks and the compressor cycles like it should w/ no crazy noises, why the heck would you replace the compressor?

The HVAC system is weird on 2013+ pathfinders though. Like I say, with my 2019 SV model. With any HVAC setting selected, could be set to hot or cold and could be 10degF outside and that **** compressor will run as well as the cooling fans. It does NOT have to be set to defrost. Bugs the hell out of me.
 

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I'm not sure why they are being replaced either since those reasons you listed are pretty much the only reasons you'd replace one. The pressures did appear normal on the one I was working on though, even though the compressor was always on. I've heard that there have been problems with cheap aftermarket compressors but can't confirm this.

The compressor in your newer model probably has a variable type where it does stay on and varies pressure output based on interior temp and evaporator temps. You can look up swash plate variable rate compressors for more info on that design.

It would be interesting to know if this issue starts after another repair. Or, a vehicle with the variable compressor had a failure where the compressor was permanently in the long stroke position, was properly replaced, but with the wrong compressor, not at their fault. Then when swapping the auto amp to the other version it works. That's probably what we are seeing here.
 

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Hi folks. I'm new to the forum. We are having an issue with erratic blower air volume output on our 2015 Pathfinder SV. On initially starting, HVAC system works normally in both a/c and heating modes. After a period of time from minutes to hours, air volume output from all vents will quickly reduce to almost nothing with no real change in blower motor sound. Reduced air flow affects aĺl vent modes, recirc and fresh air, as well as dual and single modes. Blower appears to run appropriate to blower setting, just no airflow from vents. Output from rear passenger system similarly affected. Nissan mechanic has spent hours trying to diagnose. Cabin filter replaced, intakes checked for obstructions and blower motor removed and checked. Malfuntion will continue until car is turned off and allowed to sit for a long period. (Of note, issue first appeared some weeks after repair work completed for large stone impact to underside which caused significant damage to frame, oil pan, a/c leak, drive train etc.) Does anyone have any idea what could be causing this?
I might know the issue (finger's crossed)! Check your cabin air filter. On My 2017 Pathfinder I had exact same issue. It has been at my mechanic for two weeks now so that they could figure it out. My Mechanic discovered that there is a sensor right next to the filter and since my filter was dirty/plugged it caused the sensor to overheat and the car went into survival mode and the vent doors all closed even though the blower continues to run. One would have thought that Nissan would have designed the vehicle to at least default to defrost mode but Frankly I have been disappointed in the engineering of the car for a couple of years now. Wish I had bought a Honda! Good Luck and I hope this works for you
 

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It is possible for a totally plugged cabin filter to restrict airflow, but not if it's intermittent, and I've seen some really gross ones without this ever happening. I really think it's more likely that the evaporator is freezing, especially if this is an intermittent issue. The only sensor in there that I can think of is the evap core temp sensor, and I am skeptical that this would over heat, and I can't find anything in the manual about it shutting the doors for protection. I've heard people say that before, but I don't think it actually does it.

Do you have exact details of what was noted by the mechanic that they found?

I fixed another one of these issues a few weeks ago by installing that older version ac auto amp.
 

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You're welcome. The ac auto amp is basically the brains of the ac system. It takes inputs from the buttons and sensors and processes the data to perform outputs like moving mode and blend doors, vary blower motor fan speed, or try to get the ac compressor to turn on and off in this case. It looks like the parts catalog calls it the HVAC control module. The part number for the one that was not working in this 2015 was 27760-9PB0A and the one that fixed it was 27760-3KA3A.

The part is mounted directly under the radio unit, not the display. The dash is weird on these. There are displays for the radio and hvac, but the actual units are behind them separately. They are not hard to replace. I believe the book time is 1.4 hours. You just need a tool to pop off the trim pieces that you can get from harbor freight, a Philips screwdriver, and (I believe) a t25 torx bit. I might be wrong about that bit size. There is a thin flat trim piece on the bottom of the main display screen that pops off to reveal a screw. Take that out, then you can pop off that display section. Then there are four more screws in there that come out with a bracket looking thing. I know, pictures would be better here, but it's straight forward once you feel comfortable ripping these pieces out. You feel like you're going to break them at first. Then I believe there are two more screws holding the lower panel in place, then two others at the bottom of the center section bracket that holds the radio unit where you can see that cds would slide into. The white plastic rectangle under the radio unit is the ac auto amp. Take off one of the side radio brackets then just take out the one rear torx bit in the other side, disconnect harnesses on the back and replace it. There is no programming or anything, it just goes right in.

I'll add that this is not a guaranteed fix for anyone's specific vehicle and that your should look at the data with a scantool to see if it is even possibly the reason for your problem. I am a big advocate for people doing their own repairs, but also advocate for diagnosing the problem the best you can. "I had this problem, try changing this part" can get expensive! This is also NOT what professional technicians do to find the problems, and of course everyone makes mistakes, which the customer shouldn't be paying for anyway, unless it really was part of the problem. Unfortunately there are a lot of shops who don't do much in terms of training and of course some people just suck. There are a lot of professional level diagnostic trainings out there for anyone serious about learning the basics and beyond.
I had my AC part (I don't know the name) replaced when it broke. I'm guessing the mechanic ordered the wrong one or whatever, but I was having the intermittent issue on drives over 15 minutes after they installed the new part. This solution fixed this issue for me perfectly. Bought the part on ebay and easily installed it. Car and AC are running better than ever. Thank you!
 
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