AC Stopped working

[rrowdy]

Yesterday on the way home, turned the AC on and it was working perfect then all flow stopped out of the dash vents.
I shut the AC off, got home moved the controls and it started flowing again but I know that somethings not right.
This is on an ‘04 Laramie with dual climate zones and just turned 101K.
Can someone tell me if this indicative of a blend door, recirc problem or how to diagnose this? I was dreading this day but after owning Five Ram trucks I knew it was coming. FYI, I always get on the road for good flow across the condenser before turning the AC on so I don’t think it over pressured and dumped the refrigerant charge because when the airflow out the vents is good it’s cold out of all the vents. And yes I did a search.

Thank’s in advance

 

[sag2]

When you say the flow stops, can you still hear the fan running but you have no air flow out of any positions? That is a bit unusual.

 

[rrowdy]

Yes, the blower is on but no airflow out the vents. when I put my hands down around the floor I can feel a little airflow circulating. This is weird
and I suspect a door problem in the heater box but that’s a job I’m not willing to explore just yet.

 

[sag2]

It is unusual for all air to be blocked. Perhaps a door has come completely loose. Laying the dash back is not a terrible job. There is a couple step by step procedures on here if you do a search. Also was covered in the magazine if you can find the issue.

 

[rrowdy]

Actually there was very little coming out the vents. I thought maybe the blend door came off and was blocking the blower output but when I got home
and let everything cool for awhile, I tried it again and it’s back to normal and blowing cold. I then tried the Recirc button and the door seems to be working ok.
I don’t have much experience with dual zone AC and both zones were on cold so maybe it’s something I screwed up but I still think somethings not right as its never done this before. I’ll wait and see if it craps again and go into it deeper. Taking care of and diagnosing these trucks can require a team effort. Thank you Sag for your input, I appreciate it!

 

[Ozymandias]

Frozen evaporator?

 

[DavidC]

Frozen evaporator?

Good possibility there, that would really cut off airflow.

 

[rrowdy]

Frozen evaporator?

I don’t think so Ozy, it was about 105 and hotter than that in the cab the airflow pretty much stopped within about 3-4 minutes or so. I can’t imagine the evap freezing up that quickly with the blower on high.
I was trying to think of anything that could cause this like a failing or stuck actuator? Thank’s for the input!

 

[Tuesdak]

Going out the defroster? (This heat and defrost AC can crack a windshield esp. with a rock chip in it.) An actuator sticks because of a broken door. They rarely fail and if they did would be stuck in the last mode. Likely the system did a recal of the door positions and "SNAP!" broke one.

 

[rrowdy]

Going out the defroster? (This heat and defrost AC can crack a windshield esp. with a rock chip in it.) An actuator sticks because of a broken door. They rarely fail and if they did would be stuck in the last mode. Likely the system did a recal of the door positions and "SNAP!" broke one.

Thank’s Tuesdak,

I never thought of it going out the defroster vents, it was hot as hell so I shut off the AC and opened the windows. It’s working now but if it happened
once it’ll happen again and I will certainly check the defroster vents.

 

[Ozymandias]

The Dual Zone doors very rarely fail at all, if after that four minutes everything worked fine then it will be hard to find a cause.
Did you check how clean or dirty your evaporator is? You can do this through the opening where the fan sits.

Just to mention it, i had frozen evaps before and it happens very quickly to shut down the airflow. Especially hi humidity forces it, the outside temp doesn't really matter.
-If- your core temperature sensor failed, and we know they do, then there is nothing to prevent it from freezing.
A plugged drain tube is also a cause.

 

[rrowdy]

No Ozy, I didn’t think of the Evaporator, Theres a lot of airflow out the vents though and it seems with a dirty evap, there wouldn’t be much airflow?
I can check though, when you say fan do you mean the blower that is under the glove compartment or another?

 

[Ozymandias]

Yes the blower under the dash.
Once it is out you can insert your smartphone into the opening, making a video, and so check the core for dirt.

I just have a hard time to figure out how it repaired itself in 5 minutes, hardware defects in this area are permanent.

 

[rrowdy]

Yes the blower under the dash.
Once it is out you can insert your smartphone into the opening, making a video, and so check the core for dirt.

I just have a hard time to figure out how it repaired itself in 5 minutes, hardware defects in this area are permanent.

I don’t understand it either, the AC like everything else on this truck has always been phenomenal. I went to the eye Dr, who dilated both eyes and I
could hardly see, so I started the truck turned on the AC by braille and with cold air and a smile, I left only to have it quit just a few miles later.
I tried it a few times on the way home and no joy so I shut it off. I’m going to look at my FSM to see if theres a detailed view of that air box.
The next Morning I tried it and everything appears to be working as designed.

 

[Ozymandias]

The next morning I tried it and everything appears to be working as designed.

And exactly that brings me to the point that it is not a blend door problem. If its broken its broken and stays that way. Also I've never heard that ONE broken door would block airflow entirely. Thats just not how it works.
IF a door fails the air gets either hot or cold on its own or its permanently directed to one direction - but it's not blocked at all.
And like said, the Dual Zone doesn't have that broken door problem like the Single Zones have all the time.

That said I'm running out of ideas for diagnosis.

 

[rrowdy]

Well, the FSM has a picture of a dual zone HVAC box with the locations of the actuators but reading the operation
doesn’t explain the interactions of the different doors in relation to the mode switch.
Now being that I couldn’t see the mode switch I suppose I could have had it in the defroster mode with the ac on
and perhaps that would have closed off AC to the dash vents. Now I’m just not sure. Anyway I’m going to continue
testing it to see if the problem persists.
Thank’s to everyone for their input on this even if it happens to be self inflicted.

 

[Ozymandias]

Wait, you said you had no air flow at all.
Now I'm confused.
Do you have flow or not?

 

[rrowdy]

Wait, you said you had no air flow at all.
Now I'm confused.
Do you have flow or not?

Not what I’d call flow, there was very little from the vents but there there was some, you would have to put the back of your hand against the vent to feel it and I don’t recall it being cold. Strange thing is that if your arm was placed low towards the floor you could feel some very light circulation around the floor.

 

[Ozymandias]

With "vents" you mean all off them, floor, dash and defrost, right?
And you turned the knob to all different settings but nothing changed, right?

Because, there is always a little flow from all vents, doesn't matter which setting is choosen with the knob, these blend doors do not completely seal of the channels. They leak always a little.

 

[rrowdy]

With "vents" you mean all off them, floor, dash and defrost, right?
And you turned the knob to all different settings but nothing changed, right?

Because, there is always a little flow from all vents, doesn't matter which setting is choosen with the knob, these blend doors do not completely seal of the channels. They leak always a little.

Ozy the only vents I was concerned with while on the road were the dash AC vents in the Front. and yes I think I tried all the positions on the mode switch with no change to the front dash AC vents which at the time and with the heat were the only ones I was concerned with.
With my eyes being dilated, I really couldn’t see where I was putting the mode switch.
then I shut the AC off and opened the windows until I put the truck in the garage. When everything cooled down (About 4-5 hours) I went out fired up the truck and everything appears to be working as designed even the blend/recirculation door, I’m thinking it was something I caused somehow but that makes no sense either. Go figure.