jaybone

Just got my 2011 Longhorn Laramie 6.7 a few months ago and it has 150k miles and now the A/C keeps cutting out lately. Compressor runs and air blows but stops coming out of the face vents. Im guessing its another blend door problem like my 2004 had. It does work at first start up 30 minutes later. gets hot in 95 degree Oklahoma. I haven't logged on in awhile and haven't searched deep yet ... any help?

Busboy

The "blend door" blends cold conditioned air with hot air, what you have is a mode door problem.. Cycle the "M11" fuse to reset the HVAC system, that should fix it. Wait it could be freezing the evaporator core does water drain from the drain? perhaps it's plugged. REset it anyway.

jaybone

I thought about freeze over too. Funny thing is I have never seen water under my truck..( condensation drip).. searched for the drain under the pass side.. poked around w a stick but didn't seemed clogged.. but we were just in Utah / Colorado and off road in mud for 3 weeks. Def sounds like mode or recirc door.. you can hear it creeking few seconds after shut down. Im getting ready to tear the console/dash open. Just called the dealer to confirm parts. I think I will replace them all if I can get to them. The 04- was a chore to do. I did the reset of M-11 just to see. It is currently working but doesn't have issues until driving in heat.. (which makes me think freeze over). But last time on I-40 I switched it to heat...for about 20-30 minutes trying to ... thaw it.. while my wife was nagging to hit a hotel. worked fine next day and following few weeks..

Busboy

If you have never seen condensation under the truck then you either live in a very dry area or the drain is plugged. On a humid day you will actually see the condensation line part way up the heater plenum under the dash if if's part full with water.

To unfreeze the evaporator just select vent and cold, there is no benefit to selecting heat other than to make it uncomfortable in the cab.

jaybone

Just verified it. it is draining water.. and yep its hot and humid. Well Ill try the vent/cold next time...pretty sure its the mode door or recirc door .. Ill post my findings

MikeyB

Sounds like your AC is low on freon and the evaporator is freezing up blocking the airflow.

jaybone

If it is freezing over, wouldn't air still flow thru the vents in heat mode? I did tear into it yesterday and the console access is sweet... almost too easy. I took both actuator motors out and apart.. they now just pop apart and all gears look fine, I swapped the upper vent and foot vent motors just for troubleshooting and it seems like the face vent (not sure what the nomenclature is) might be the issue since the door is the only part that stopped the airflow when messing with it when operating. It still seems to have low flow on high settings and doesn't seem to make any difference when recirc is pushed. I can hear it ... gets louder in the cab and does cut off and on but makes no difference to airflow. Maybe Im expecting it to blow my hair back and its working like it should. I even tried blocking rear vents but no difference, the blend door is working as heat comes out pass side and ac out drivers side with dual climate changed to different settings. It did make a creaking noise still upon shut down in the glove box area with both motors removed.. , I dug around, pulled the fan out saw the fresh/air door.. it works as it should and couldn't see anything else... so Im still suspicious of another door I haven't found yet. Of course the creaking noise quit and all seems to be working fine. Wife is taking the truck on 6 hr drive today.. Guess Ill know soon.

MikeyB

Not sure with the 4th gens but on the 3rd gens air flow is shared with both the heater and evaporator cores. So if the evaporator freezes up there is no air flow through the vents in any mode. Just have to turn the AC off but leave the fan running to help melt the ice quicker. Just went through this two months ago with my truck.

RamGazer

If you do replace the doors go with Heater Treater | HeaterTreater.com They are the best for replacing those doors.

Busboy

ALL air coming from the blower fan FIRST passes through the evaporator, the blend door then allows varying amounts of this air through the heater core and out the other side where it is mixed with the pure cold air that bypassed the heater core. If the evaporator is freezing or partially freezing then airflow is reduced as air can't flow through a block of ice. As MikeyB says it could be that it's slightly low on freon, it could be a partial blockage of the fixed orifice. You first need to determine if it is freezing then throw a set of gauges on, topping up the refrigerant is easy the fixed orifice is not so much. This requires the line to be replaced and the system evacuated and recharged but I would also replace the dryer at the same time.

jaybone

thanks for the input.. I used the heater treater on my 3rd gen. The girls are out w my truck to our cabin and no issues on the 3.5 hr drive in 95 degrees yesterday. Ill top off the Freon upon return if needed and go from there, it might need the orifice replaced as I did notice the front end had been repaired or at least the right front inner fender well and fog light. love how you find these things afterwards

jaybone

Well its still broke, all worked fine for 380 miles and the last 40 it quit. I knew right away when she walked in the house hot n sweaty.. Sorta guess it was froze over as the puddle grew under it for about 2 hrs. I let it sit for about 6 hours started it up and the compressor wont stay engaged, put my cheapo low press gage w a can of Freon attached and I did get one can in when the compressor cycled but no joy. Its going to repair shop this week since I cant work on it due to just having back surgery and cant even bend over yet. Anyone know the location of the low pressure switch and my last ditch effort to bypass it.

jaybone

Next day... it works fine. Freon is low for sure (30 psi @ 90 degrees) and the compressor stays engaged now. I assume I didn't get much Freon in it yesterday or the system was blocked or restricted. I read in another post that there is no longer a low press switch but some type of evaporator probe that cycles the compressor..?

I am sure there is still an issue with airflow so I pulled the glove boxes.. verified the blend door actuator.. its working but creaking noise behind it. I verified the recirc door works like it should.. its easy to see w glove box out. Fan motor doesn't seem to change speed to the last max setting. Tested fan in my hand and it will not go to max. Voltage test on fan pug 12.50 next lower setting 11.48 and so on. So I assume the blower motor is bad. Tired to disassemble it.. and the dirt that covered the bench is excessive, There is a phillips screw on the rear of the fan housing but couldn't get the thing apart. I oiled it reinstalled the motor and its now bent.. New blower motor is next.

If there is that much dirt/dust on just the fan I can guess the evaporator has to be nasty. Is there anyway to clean it? This thing is not going to beat me. Ill keep ya posted.

jaybone

I got the fan motor broke down to parade rest. Cleaned and reassembled and now works as it should on max hi. Pulled the resistor block and could see the evaporator w a light and mirror and its filthy. Its covered w dust and dirt to the point that it must be cleaned. Any suggestions .. I am about to shove a garden hose and squeeze..

Ive got some pics to post... soon

I am pretty convinced the mix of low Freon, fan wouldn't go to high and the dirty evaporator is the issue?

Busboy

You can buy evaporator cleaner designed specifically for that purpose but you also need to do the cabin air filter mod that will keep all that junk out.



https://www.dieseltruckresource.com/...er-mod-284729/