JL A/C

[Bucaro]

Sorry to hear. So far it has worked for me...

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[DanFelix]

I tried this, several times, with the wife feeling the hot air on her feet. It didn't work.

The valve to the Recirculation Plenum (behind the glove box with the cabin air filter) is not binary. It is closed if the Recirc button is off and the fan is in 0-3 speed. At 4-7 speed the valve partially opens to the cabin, maybe 20%, regardless of any other HVAC setting. It will fully open if the Recirc button is on, which automatically turns on the A/C. So, air has a way to blast out of the plenum IF the pressure in the plenum is positive, not negative as it should be. That is another explanation.

 

[Khsonic03]

I just went to the dealer to have the TSB referenced earlier in this thread performed. They told me my software was up to date, which is impossible since this TSB came out after the last time I had been to the dealer.

They did some other software updates while I was there, so maybe it somehow got updated and they didn't realize it? Either way, I am still having the issue after the dealer visit.

 

[Iggy]

I wonder if it is a 'feature' of the recirculating air function. Does it do the same thing when drawing outside air versus doing the recirculating function?

Another amazing engineering and design exercise on these $50,000 utility vehicles.

 

[DanFelix]

I wonder if it is a 'feature' of the recirculating air function. Does it do the same thing when drawing outside air versus doing the recirculating function?

Another amazing engineering and design exercise on these $50,000 utility vehicles.

According to the wiring diagram, there are two fans. The Outside Air Inlet Drive which draws air from the outside vents and delivers it to the Cabin Filter Plenum (box) behind the glove box. The other fan is behind the filter at the bottom of the plenum and is the Recirculation Air Inlet Drive. It pulls air out of the plenum, through the filter and down the system where it is cooled/heated and routed. The plenum itself has a gate that can open or close into the cabin, explained earlier (#32). Normally the plenum has a negative pressure but if the Outside Air Inlet fan exceeds the Recirculation Air Inlet fan then the plenum will overflow and dump outside air on the passenger side. Multiple errors have to occur for that to happen.

I suspect it is not a feature since there are so many owners that have not experienced it, myself included, and I doubt that modern car makers would design a system that intentionally by-passes the cabin air filter. I think it is a failed coordination between the fans and the recirculation gate in the plenum. It would be interesting to see the build dates for all those that have the problem and see if there is a pattern. My two cents worth.

 

[Iggy]

According to the wiring diagram, there are two fans. The Outside Air Inlet Drive which draws air from the outside vents and delivers it to the Cabin Filter Plenum (box) behind the glove box. The other fan is behind the filter at the bottom of the plenum and is the Recirculation Air Inlet Drive. It pulls air out of the plenum, through the filter and down the system where it is cooled/heated and routed. The plenum itself has a gate that can open or close into the cabin, explained earlier (#32). Normally the plenum has a negative pressure but if the Outside Air Inlet fan exceeds the Recirculation Air Inlet fan then the plenum will overflow and dump outside air on the passenger side. Multiple errors have to occur for that to happen.

I suspect it is not a feature since there are so many owners that have not experienced it, myself included, and I doubt that modern car makers would design a system that intentionally by-passes the cabin air filter. I think it is a failed coordination between the fans and the recirculation gate in the plenum. It would be interesting to see the build dates for all those that have the problem and see if there is a pattern. My two cents worth.

Your explanation makes sense and causes me to think you're a technical writer by trade. Or maybe a lawyer, but thank you for clarifying it.

 

[iznthesky]

I have a 2018 JL with auto climate control. Running a/c in auto mode, every few minutes heat will come from under the dash. A/C continues to blow cold from dash vents, but heated air comes from under the dash. Service Mgr at my dealer says this is normal, as it is trying to maintain set temp. I also have a 2019 Ram 1200 with ATC that doesn't do that. ATC should use a blend door to mix warm and cold air to maintain cabin set temp, not give you a blast of hot air. Is this a fact of life with a JL?

FINALLY.........IAM NOT ALONE ! ! !
I occasionally experience the same flow of warm damp air....it’s a buzz-kill. I too was told that it’s the Auto-Temp control.
as soon as I detect this air mixture..... I switch from fresh air intake to recirculating air....Or vise versa....this immediately stops the Auto-Temp warm air. Wish that I could prevent this temp control warm air from invading the cockpit. It’s not often enough to really be in issue....but yes it’s annoying when it does kick in.

 

[KDoc]

Strange ... I live in Queensland Australia where our summer get up in the high 30 Celsius . We have a 2019 Sahara (branded as an Overland here due to Toyota already using the Sahara label) and have not had that problem at all and we have the AC on virtually all year round .

 

[tkmo061]

Have the same annoying "feature" on my 2020 JLURR and experienced it on two week-long JLU Sahara rentals I had in Hawaii late last year. I fixed it on my Rubicon by taking the hard top off - now I don't even notice!

 

[Jjirish]

I have a 2018 JL and live in SoCal. 100+ deg for a couple of weeks. I have never experienced hot air from under the dash and I use the Auto A/C. It almost sounds like a missing or loose air conduit that should be blending the air.

Never had a jeep that didn't dump hot air on my feet every now and then. I keep thinking my next jeep will have this issue resolved.... maybe future jeep #8 will.... fingers crossed.

 

[Iggy]

Never had a jeep that didn't dump hot air on my feet every now and then. I keep thinking my next jeep will have this issue resolved.... maybe future jeep #8 will.... fingers crossed.

Why would they spend money on engineering a solution when we buy their products as fast as they make them? We're all guilty.

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