A/C compressor not running in Defrost mode

[ArnieC]

EDIT - Broken recirc door - nothing to see here.

I started another thread with my repair method and a better title for searching.
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Original post

Was quickly reminded of an issue with my 2015 LC this morning as temps dropped into the teens here in Wisconsin and my windows started fogging up with defrost on during my morning commute. - approx 20F ambient temps

Got to work and popped the hood and the A/C compressor was not running. Should it be? A/C light on the climate display is on solid and the A/C cools well in the summer. Its not "freeze you out" but it is comfortable.

Vehicle was brought from the south last year so it never saw cold until the second half of last winter.

Thinking I am probably a little light on refrigerant, when it is cold the low side pressure is too low to get the compressor to engage. I was gonna throw a squirt in over the weekend or at least hook my gauges up and check system pressure and see if the compressor kicks on. Does Techstream monitor the HVAC system? Is my thinking sound?

Anyone wanna tell me the low side threshold for the system to engage?

 

[gaijin]

Was quickly reminded of an issue with my 2015 LC this morning as temps dropped into the teens here in Wisconsin and my windows started fogging up with defrost on during my morning commute. - approx 20F ambient temps

Got to work and popped the hood and the A/C compressor was not running. Should it be? A/C light on the climate display is on solid and the A/C cools well in the summer. Its not "freeze you out" but it is comfortable.

Vehicle was brought from the south last year so it never saw cold until the second half of last winter.

Thinking I am probably a little light on refrigerant, when it is cold the low side pressure is too low to get the compressor to engage. I was gonna throw a squirt in over the weekend or at least hook my gauges up and check system pressure and see if the compressor kicks on. Does Techstream monitor the HVAC system? Is my thinking sound?

Anyone wanna tell me the low side threshold for the system to engage?

My memory is a little foggy on exact cut-off temp, but it is normal for the AC compressor NOT to turn on below approximately 40 degrees F ambient temperature.

HTH

 

[cboyd]

this seems correct in my mind, as below certain temperatures just having the outside air (not recirc) offers the same or better temperature and less humid air without risking compressor freezing.

I'm having the same issue with fogging just starting with the onset of cold, but hadn't noticed if the compressor was coming on or not. I'll keep an eye with our temps going down into the 20s/30s over the next few days

 

[ArnieC]

My rig is set to outside air, air filter is good and recirc door works. Still fogs. Interior is dry with no leaks. Cant figure it out.

 

[bloc]

My 2013 manual says AC system may not operate "when outside temperature approaches 32F". p345 if anyone is curious. I'm assuming this is a limitation of the refrigerant system itself and applies to defrost mode also.

 

[OregonLC]

At 20F there shouldn't be enough moisture in the air to fog up the inside of the glass. The purpose of running the A/C is to condense the water out of the air to help with the defog (this is the water you see dripping on the ground), but at those temps the relative humidity should be really low. Is there a moisture source in the car which needs to be addressed?

As others have said, this is correct operating behavior. You don't want your coils freezing up or an ice dam in your condensate drain. You'll also notice that your center console fridge doesn't work in the winter.

 

[ArnieC]

Car is bone dry with no smells and no evidence of water anywhere. That's why I am mystified

 

[KLF]

The AC system has (as pretty much all of them do, even your home units) a low temp setting where the compressor will not turn on. This keeps the evaporator coil from freezing over, due to the condensation on the coil getting hit by below freezing incoming air.

Normal behavior.

 

[Sinister]

If your windows are fogging up, check that the re-circulation door is not busted. If you’re only drawing inside air you’ll fog up for sure.

 

[ArnieC]

OK I gotta eat some crow on this one boys.

I always thought my recirc door was functioning fine since when I put it in recirc to check my air filter, it was fine. Turns out it was busted like most of them are and stuck in recirc Rig is currently apart and I think I came up with a pretty good and unique fix including being able to remove the door to work on it on the bench without disassembling the dash or cutting up the airbox. If I had a 3D printer I would have been even more dangerous.

Will see how it all goes back together tomorrow and then if it works will post my solution.

 

[cboyd]

well thanks to this thread I have also found the source of my fogging I took a trip up to Vermont this past week (to pickup some RockWarriors) and I could not keep the rig from fogging up without running the system in manual front defrost with the fan halfway the entire time. we were getting light snow and temps down in the upper 20's.

@Sinister point above got me thinking, so I went out to check it. I agree, if there is only inside air, it wasn't going to go clear, and even with the manual front fan going, the rest of the side and rear windows were fogging.

turns out my recirculator door is not completely broken. when I opened the door, the door was in the recirc position and I could clearly see the filter - yet the system was in fresh mode. Uh, not good and explains the recent fogging.

I pulled the filter to inspect the hinges and could not see any of the damage to the hinges others have shown in photos. Out of curiosity to see if was just stripped liked some have reported, I gave it the most gentle tug forward and it closed. when I hit the button to put it back in recirc - it opened! I tested each time and it would not open for fresh, but if I manually closed it, it would open for recirc.

does this mean one of my linkages to the servo is just popped off? Are there two servos, one for fresh (close) and one for recirc (open)?

waiting to see what @ArnieC figures out on how to pull it all apart... so I can go in for a closer look.

 

[bloc]

Hard to say exactly what’s going on but I agree the fact that it moves one way is encouraging. Remove your glove box and have a look

 

[ArnieC]

Fixed it - was a broken recirc door.
My method below.

Broken fresh air/recirc door fix

My 2015 Land Cruiser had a problem fogging the windows any time the temps dropped below freezing. I thought I had a functional fresh air/recirc door because when I went to change the filter, I put it in recirc and it was in the right position. Turns out the door was in fact broken and stuck in...

forum.ih8mud.com

CBoyd - you either have a stuck actuator due to dirt or debris or a broken door that is just not readily apparent. It is only one actuator for both positions. Linkages are very minimal, mainly a pivoting arm.

Once the glovebox is removed its pretty easy to at least ID the issue but not always super easy to fix.

 

[CharlieS]

I only have one point of reference: my pivot (the female part on the flap) where the servo arm attached was cracked/broken, and the servo arm was fine. Yes, one servo/arm controls movement in both directions. I was able to reinsert the servo arm and it moved the flap one direction but wouldn't move the flap in the other, due to the location of the break. I'd take a really close look at the female part where the male section of the servo arm goes for breakage.