Hello,

When I go on long drives (1.5-2+ hours) during the summer time, my air blows normal and cold then after about an hour or so my air stops coming out of the vents. I can still hear the air blowing hard but I don’t know where it’s going. I’ve tried switch the air to the floor vents, turn ac off and on but nothing works until I get to my destination and the car sits for a while. I found this post here:


post6755261.html?hilit=AC%20freezing#p6755261


I don’t really understand how to diagnose this problem. It seems like there’s something freezing on these long drives but why would that block all the airflow out of the vents?
The day after my most recent trip, I tried shoving about a foot of weed wacker wire up through the evaporator drain hose but it didn’t seem to make a difference. No water came pouring out like I had hoped. I don’t want to take my car into a shop because this only happens on long drives in the summer (90+ degree temp). Anyone else had this issue?

EDIT: I also wanted to add this is a relatively new probe that’s happened over the past year or two. I have never had to do anything with the AC system/Freon.

The culprit is probably your Thermal Expansion Valve (TXV). It sits in the firewall at the inlet/outlet of the evaporator and regulates how much refrigerant enters the evap based on the evap's temperature. They use a wax expansion element like an engine thermostat and can often stick open. That causes the evap to become a block of ice after driving for awhile, especially in humid conditions with a high cooling load.

So it’s probably a bad Thermal Expansion Valve? When my air stops blowing I get very little air blowing out but the air coming out of my vents is still cold.

Is there anyway to fix the thermal expansion valve without draining the whole system of Freon?

Ekinike wrote: ↑

Sat Jul 02, 2022 2:10 pm

So it’s probably a bad Thermal Expansion Valve? When my air stops blowing I get very little air blowing out but the air coming out of my vents is still cold.

The airflow goes to nothing and the air is still cold because the evap is turning into a block of ice and not a mini-radiator. The ice is preventing most of the air from the blower from getting through the fins. But the air that does get through is still passing through an iceberg.

Ekinike wrote: ↑

Sat Jul 02, 2022 2:10 pm

Is there anyway to fix the thermal expansion valve without draining the whole system of Freon?

No, the system has to be evacuated and then vented to atmosphere before you can pull the lines, then evac'd again and recharged when you're done. The TXV itself is easy to swap out (one screw and four o-rings), but getting at it on a gen2 Rogue requires pulling the wiper motor and cowl. That's not terribly difficult, it's all 10mm screws other than the 14mm nuts on the wiper arms, but the plastic cowl cover can be a PITA if you haven't done one before. If you DIY it, make sure to use new o-rings and apply a thin coating of PAG oil or vaseline so they slide in without nicks or folds.

That makes a lot of sense. Thank you for the explanation. I have a trip coming up. When it happens again I’ll pull over and see if that expansion valve is icy and give an update.

It isn't the TXV itself that ices up, its the evap (27280 in the diagram I posted). It's buried inside the HVAC housing, so it's pretty immune to touchy-feely testing. Here's a pic of the actual part:

As you can see, it's like a mini-radiator, it's just absorbing heat instead of dumping it. Next time the A/C quits working, pull the car over and shut it off, wait ten minutes, then fire back up. If suddenly the A/C works again, it's because the evap was frozen and you let the ice melt. That's the smoking gun for diagnosis on this particular problem, along with loss of airflow which you've already confirmed. I should also note that the TXV's are a fairly frequent failure point on gen2's. Not like we see one every day, but probably at least 2~3 a month during the summer.

You might want to start by having an AC shop evac and recharge the system. It could just be low on charge from a leak in the lines. That can cause EVAP icing issues.

Hello Dan,
I will check the Freon charge on it but I’m probably going to end up doing the TXV replacement. I went on a long drive today and the same thing happened. Once the AC froze and quit blowing I pulled over for 10 minutes and then it worked again! I’ve never had an issue where the air was blowing warm so I don’t think it’s low on Freon, but I will check before I do the replacement. Thanks for the idea.

Vstar650L,
Thanks you for all your help! This has been a lingering problem for the past couple years that has been difficult to diagnose due to the ac failure only happening on long drives. I really appreciate you taking the time to be so thorough. I don’t think there are many people with your experience who could diagnose this issue as quickly as you have. I will post a followup on this forum to help others who might have the same problem.

Ekinike wrote: ↑

Sun Jul 03, 2022 1:37 pm

Thanks you for all your help! This has been a lingering problem for the past couple years that has been difficult to diagnose due to the ac failure only happening on long drives. I really appreciate you taking the time to be so thorough. I don’t think there are many people with your experience who could diagnose this issue as quickly as you have. I will post a followup on this forum to help others who might have the same problem.

You're most welcome, glad I could help. The A/C coming back online after a stop is pretty much a smoking gun. FYI, the spotty earlier failures aresn't unusual either. The TXV has a wax element just like a thermostat, so freezing up in fits-and -starts prior to failing completely is very common.

I have not experienced this issue, but am curious if simply turning the AC off and running the vent without engaging the AC compressor for 10-15 minutes would accomplish the same thing as pulling over and stopping the engine?

Lone Wolff wrote: ↑

Sun Jul 03, 2022 8:19 pm

I have not experienced this issue, but am curious if simply turning the AC off and running the vent without engaging the AC compressor for 10-15 minutes would accomplish the same thing as pulling over and stopping the engine?

Yes. A stuck-open TXV simply ices-over the evap fins, so killing the compressor in any fashion will let the ice melt and temporarily clear it up. If you have similar symptoms but turning the compressor off doesn't resolve it, it probably means a slow or blocked drain hose that's covering the evap with liquid water.