# Loss of AC airflow after about 2 hours driving



## Ady (May 5, 2014)

Hi guys,

OK. I've started getting this issue on longer drives (+2 hours). The AC works fine and then the cabin temp starts to increase without any interaction with the system. This has occurred a couple of times now. The fan still operates but there's very little airflow from any of the vents regardless of what mode is selected.

The first time, the system righted itself while it was parked up. The second time, I tried disconnecting the battery for a couple of minutes to reset the system but that didn't work so I did a little research. The schematic suggests that the only single damper (or 'door' as Nissan calls them) that can have this effect is the 'Upper Air Mix Door' which, together with the Lower Air Mix Door, controls air temp by directing a portion of airflow via the heater matrix as required. If this is shut as well as the Lower Air Mix Door, no airflow can enter the cabin. With this in mind, I was going to test the theory by increasing the temp setting to max to force the Lower Air Mix Door open to allow airflow through the Heater Matrix into the cabin. However, when I attempted this, the system was working fine again! Frustrating, I know. I now have to wait for it to fail again before I can investigate further.

The car is still under warranty but there's not much point taking it to the dealer unless there's actually something wrong with it. I guess I'll have to wait until the failures become more frequent or it fails altogether but with ambient temperature here regularly in the late 30s to early 40s (deg C) that's a prospect I'm not looking forward to!

So, I'm thinking there's either something mechanically wrong with the Upper Air Mix Door which realigns itself after a while or possibly the first signs of a failing A/C Auto Amp which drives all of the dampers (doors) in the system

Since the AC system doesn't respond to an increase in cabin temp by increasing fan speed (in auto) I'm thinking that it's the A/C Auto Amp.

I welcome anyone's thoughts on this.

Thanks

Ady


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## Ady (May 5, 2014)

Sorry, I forgot to mention. There are no fault codes.


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## MikeHJ (Mar 7, 2017)

There's a whole set of troubleshooting and diagnostic procedures in the AC section of the service manual.


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## Bertoknee (Oct 19, 2018)

old thread I know ...but I have this exact problem on my 2010 T31.... after about 1.5 - 2hrs of use. Blower fan is still turning fast ..can hear it ..but there is very little airflow out of vents. Now...I never thought about it being a problem on the Inlet side of things, BEFORE the fan .... so I concentrated on the outlet side...AFTER the fan ..and actually there is very little that can obstruct between fan and vent..just filter..and evaporator or heater matrix.

Its not my filter..its new...so Im thinking the evap is freezing?? .... fan working fine..but no airflow can get thro the evap... cos its iced up? ... Ive
checked and double checked all the sensors...like evap inlet temp sensor..this is what tells AC auto amp to de-clutch the compressor when temps get too close to freezing... it measures ok ...and it compares ok with a new one. Compressor is cycling ok when I disconnect the sensor ..so the auto amp seems to be doing its job....

after researching online .. it seems that low refridgerant pressure is a common cause of icing up...so they say anyway ...gonna get my refrigerant pressure checked. When it works the airflow is cold ... but still gonna get pressure checked first opportunity...if only to cross it off the list.

Also..like the OP ...mine fixes itself after about 10mins turned off ....which again points to freezing evap. defrosting naturally. I do notice A LOT of condensate under the car too after its switched off ..more than is normal I think ..again points to defrosting. Next time it happens while driving I'm gonna manually sw. off a/c ..keep blower fan at max and open the flap for outside air .... that should defrost the evap. quickly. If this does the trick..and good airflow is restored...then Im pretty sure it must be evap. icing caused by low pressure refrigerant....

Like the OP tho ...I have to wait for it to fail before I investigate or diagnose further ...and that means doing long drives... its very frustrating indeed.


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## Bertoknee (Oct 19, 2018)

well I finally managed to get the refridgerant pressure checked ..and it was fine .. ? ....so ...im no further forward ... everything seems to work fine..until 1.5 - 2hrs ...then ..no airflow.

gotta take the dash apart again..and check n re-check everything .... 

possibly some dry solder joint inside the Auto amp is the culprit ..... might have to get that out and split it...

I much prefer manual a/c systems .... seldom get any of these kind of problems ...


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## quadraria10 (Jul 6, 2010)

Sounds to me like your evaporator is freezing up and becoming a block of ice. My guess is conditions are very hot and humid, and the air con is always set on fresh air from the outside. Does it do the same thing if you keep the air setting on recirculate, as that would put less load on the system. Possibly linked to clogged cabin air filter that is restricting air flow?
There is no point taking your dash apart if you are getting normal ac for the first two hours of a long drive in +30C temps, as the system obviously works. At least that is my take.


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## Bertoknee (Oct 19, 2018)

..I too, reckoned it was a freezing evap. causing the problem. I normally drive it in recirculate...very seldom on fresh air ..unless it was on Auto perhaps and had opened that outside flap without me noticing ..unlikely, but possible.
In any event..the evap sensor & auto amp should prevent a freeze up...i think it's that system that is failing after 1.5hrs....
The cabin filter is brand new so I dont think that is the issue ..and as I say..works fine for the first 1.5hrs or so.
The evap sensor measures ok..and its resistance varies as it should. 
That really only leaves the auto amp ..that is maybe failing after 1.5hrs ...and not cycling the compressor as it should when the evap temp gets too low....
gonna get it out and take a look at the board...see what I find in there...

be nice to know if the OP got anywhere 
with his problem....


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## quadraria10 (Jul 6, 2010)

Not sure what you mean by the auto amp. I am guessing you mean the fan blower control unit amplifier or resistor, depending upon the type of system you have. Again though, your system seems to work properly, its just that after 1.5 to 2 hours driving in certain heat conditions your evaporator is most likely freezing over.
I was just reading a bmw thread about the same thing, though for that poster it occurs after roughly 3 hours. Seems like if you have the cool setting at too low a temp and the fan going at a low speed this happens. I would experiment with setting the cabin temp a bit higher ( not on lowest setting on hottest day) and keeping the fan speed on a higher setting. Also noticed you are in Australia. Have you checked the Aussie X trail forum? Maybe someone there has more experience with the issue?
These days in Canada keeping the cabin warm is more of an issue that cooling it down lol.


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## quadraria10 (Jul 6, 2010)

You might find this thread interesting, and maybe it contains some info to help you.
AUSTRALIAN X-TRAIL FORUM :: Technical Problems & Solutions :: Is your Aircond cool enough? | Runboard


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## Bertoknee (Oct 19, 2018)

..ok
im not in Aus ...I'm in the Philippines.
a/c auto amp is what Nissan call the control unit..the bit with the dials on it.
the fan speed is never low ..its always over half way ...often max.
i have searched all x trail forums known to me for another similar fault ..this is the only thread I found.
the temp setting that I select cannot be 'too low' to cause these symptoms..I set temp. and the system tries to cool down the cabin best it can. 
As I said before tho .... if it is working correctly, it should NEVER freeze up the evap ...because there is a control loop in place to prevent that. The auto amp with input from evap sensor should cycle the compressor clutch to maintain evap temp LOW...but NOT near freezing. That's how it should work ...but I suspect that control loop is failing after 1.5hrs or so. 
So ... either of those 2 items has an issue ...measuring & testing is difficult..because the fault condition doesnt arise until after 1.5 hrs of operation ...so..I am left with inspecting components to see what I can find. I have a replacement evap sensor..but they are a pain to replace. So firstly I shall remove the a/c auto amp and have a good look at it ...maybe run an iron over everything....


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## Bertoknee (Oct 19, 2018)

..im all over the Aussie X Trail forum too .... read that thread before .... as I said..only time I've seen this particular problem mentioned has been on this forum .... be great to hear of a 3rd T31 with this issue but seems not...


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## quadraria10 (Jul 6, 2010)

Well I hope you can figure it out. You seem to know a lot more about the functioning of the system than I do. Good luck with it.


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## Bertoknee (Oct 19, 2018)

cheers ...I appreciate the input ... I will get there ..just might take some doing all the 1.5hr journeys..lol


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## Bertoknee (Oct 19, 2018)

well...its taken a while to diagnose this fault.... given it needs 1.5hrs or so of operation to show its face...but I'm now as certain as I can be that a freezing evaporator is the cause. Twice now i have been driving the prerequisite 1.5hrs and the fault has appeared ..ie. the airflow from the vents has reduced significantly to the point where the aircon cannot keep the cabin cool. Both times this has happened the blower can still be heard running at full speed...just no airflow..or very little.

So ... each time it's happened ....i have turned off the aircon manually using the centre button on the fan dial ...but kept all other settings the same. Within 2/3 minutes ..the airflow was restored to normal and the cabin cools down again. 

This can only be because of a frozen evaporator ... that defrosts ... once the compressor is disabled. 

All I need to do now...is figure out which component is failing at the 1.5hr point ..its either the evap temp sensor ( cheap, but difficult to replace) ...or the auto amp ( expensive, but easy to replace!) .

Having bought a replacement evap sensor already..and compared its readings with the existing one... I'm .pretty confident that its not that. Which leaves the main auto amp ( aircon control unit). Unfortunately..they are 300+ $$ to buy new .. and there are several different variants. Mine is a lhd version (fan on left) ... and its a 27500 JG44A ... which is rare as hens teeth!!

I would just buy another ebay lhd version for about £90..but the plug(s) are different ...virtually all other versions have 1 large rectangular plug on the rear ... but mine has 2 smaller ones side by side! ... 

So..until I find a replacement on ebay at a decent price ... Im kinda stuck with the problem. At least I now know how to defrost the evap quickly while on the move tho..thank goodness..


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## quadraria10 (Jul 6, 2010)

Glad you have it figured out. I am not convinced changing either the sensor or the control unit will make a difference. It might just be that you are pushing the systems performance limits. Kind of like how some in Canada complain about the car being slow to heat when the temperature outside is -20 or below.


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## Bertoknee (Oct 19, 2018)

i dont believe the symptoms are those of an aircon system reaching its limits. 

Fact is that the fan is going full ..but there is little airflow from the vents ...which must mean an obstruction of some sort. Given that there is only the filter & evaporator between fan and vent ...it must be one if them causing it. It isnt the filter ..i had the symptoms while it was removed temporarily. Which only leaves the evaporator. 
As further proof, 3mins after disengaging the compressor the airflow is back to full strength again .... that really can only be as a result of the evaporator defrosting - nothing else changes.

I had the back off the control unit... with a view to running a soldering iron over everything just in case a dry joint was causing all this. Sadly..the pcb looks a multi layer affair with a high concentration of surface mount components ..in short, its not the sort of board that will take too kindly to a hand held iron ...
So ... looking to replace..if poss..at reasonable cost of course.


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## otomodo (May 23, 2008)

I have a dehumidifier that is low on freon and it freezes half way to the serpentine. 
My home ac was low on freon and it couldn't generate all the heat it was suppose to do. The serpentine outside had frost only 8cm high. 
After a check up and a fill everything now is back to normal. 

Have you checked both switches, high and low?


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## Bertoknee (Oct 19, 2018)

i have had the refridgerant level checked and yes, it was fine ... I have not checked the operation of any high & low switches so I may do that ..thanks.
Remember tho ..the system operates perfectly for 1.5 - 2hrs ... and can be 'fixed' by manually de-clutching the compressor for a few mins. I'm not sure a switch issue would cause the system to react like this... but I will certainly check them.


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## Xtrail owner (Jul 9, 2021)

I have similar problem but the air con goes off after about five seconds. Fans work, ac works just doesn't blow. Garage says everything working fine, fluid levels okay. Real pain as it is still under warranty. Can only get ac by turning off and back on using the console and then only get a two second blast.


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## VStar650CL (Nov 12, 2020)

If the fan and compressor are still spinning then it sounds like your airflow is obstructed. Three possibilities to check, a clogged cabin filter, debris in the cowl blocking the intake, or a blocked evap drain hose that's "drowning" the evaporator.


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## John 1111 (Jul 16, 2021)

Bertoknee I have exactly the same problem. Air flow stops after a couple of hours driving. I worked out the same as you, the evaporator must be freezing up as when I knock off the AC for a couple of minutes the air flow starts again. I suspect air isn’t blowing correctly over the evaporator leading to it freezing. It could be there’s something wrong with the vent alignment as one vent blows really cold air whilst the adjacent one is not as cold as it should be but I’ve no idea how to check that out without dismantling the whole dashboard. Could also be dirt in the evaporator fins blocking air flow. Again can’t check that out without major dismantling. Sorry no solutions, just possible causes. Would be interested to hear if you’ve managed to find a solution.


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## BobP (Jul 19, 2021)

Hello,

I am having the same problem with my AC on my 2015 pathfinder. During long drives of 1.5 hours or more suddenly there is no air blowing from the vents. I turn it off and wait for a few minutes then turn AC on again, recirculate and the blower and air is cold. but after a few minutes again the air blows poorly. The next day while driving in the city the AC was working fine. This usually happens on my long drive and the outside air temp is 28 to 30 degrees hot. I wonder if this is a serious fix.


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## John 1111 (Jul 16, 2021)

Update with my aircon - it does seems that freezing up is a sign of low refrigerant levels, as mentioned be others earlier. A few days after mine starting to freeze up on the xtrail, it has pretty much stopped cooling altogether. Trying to get a regas booked.


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## Paweks (Jul 28, 2021)

I have the same exact problem with my xtrail 2015


Bertoknee said:


> i dont believe the symptoms are those of an aircon system reaching its limits.
> 
> Fact is that the fan is going full ..but there is little airflow from the vents ...which must mean an obstruction of some sort. Given that there is only the filter & evaporator between fan and vent ...it must be one if them causing it. It isnt the filter ..i had the symptoms while it was removed temporarily. Which only leaves the evaporator.
> As further proof, 3mins after disengaging the compressor the airflow is back to full strength again .... that really can only be as a result of the evaporator defrosting - nothing else changes.
> ...


Bertoknee I have this same exact problem with my xtrail 2015, and also the solution is the same to regain the airflow black. Please, update here if you have the solution I'm from Philippines also.


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## nazhos503 (5 mo ago)

can anyone from NISSAN chime in here to help with their product ?


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## VStar650CL (Nov 12, 2020)

nazhos503 said:


> can anyone from NISSAN chime in here to help with their product ?


We don't have Exxie documentation here in the 'States, but chances are your rides have Thermal Expansion Valves (TXV's) and those are causing your freeze-ups. The TXV is like a reverse thermostat, it's supposed to close and cut off refrigerant flow when the evap gets too cold. If the valve fails and sticks open, condensation on the evap gradually turns it into a block of ice, Cycling the system or shutting the car off briefly melts the ice and it begins working again.








A/C issues location of expansion valve


Hello. It is so hot and I guess I forgot that last summer the ac in my car 2016 Nissan Altima S 2.4L did not seem to keep cool. Yesterday I drove 600 miles to south Texas and A/c cooled sometime and sometime not. When I got back I put my gauges on the low and the high side and got no psi. I...




www.nissanforums.com


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## otomodo (May 23, 2008)

nazhos503 said:


> can anyone from NISSAN chime in here to help with their product ?


Nissan won't send theirs technicians search forums to help people with their car. Go to the dealership to get it fix,that's how they make money. 
Vstar answers here voluntarily (i assume) and probably asks questions elsewhere for his other brands cars.
That's how it works in this  .


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## nazhos503 (5 mo ago)

does anyone from NISSAN have anything to say on this matter ?


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## VStar650CL (Nov 12, 2020)

I'm a Nissan tech, friend. If your A/C quits after running for awhile and the airflow drops off, it's almost certainly a bad TXV Valve causing your evap to ice up.


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## kaandemir (30 d ago)

Ady said:


> Hi guys,
> 
> OK. I've started getting this issue on longer drives (+2 hours). The AC works fine and then the cabin temp starts to increase without any interaction with the system. This has occurred a couple of times now. The fan still operates but there's very little airflow from any of the vents regardless of what mode is selected.
> Speed Test
> ...


Does it do the same thing if you keep the air setting on recirculate, as that would put less load on the system. Possibly linked to clogged cabin air filter that is restricting air flow?


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