All right, the A/C was working great one minute, then phhhht....

It has pressure in the lines, the clutch is engaging, the high side line going FROM the compressor to
the evaporator is HOT, the one going from the evaporator to the firewall is so cold that the
condensation freezes within a few minutes.

And here is where the problem begins, I get no cold air from the vents.
I have checked the dashboard vacuum lines, all that seems to be working, the controls, too.
All the fuses are good.

Now the line coming back out from the firewall that leads to the Receiver / Dryer ...
The dryer itself, and the line leading from that to the compressor are about room temperature...

Any ideas?

 

could be a mode door problem. when you switch the diff modes on the dash do they change to where the air supposed to come out? ( dash , foot, defrost) if not you may have a vac leak to the heater bo. dont jump on me and tell me it s not vacume controlled I dont know what year you have . if it uses elec servos you may have a broken mode door. you can hear or feel the blower motor working ?

 

A 173 posts and still NO info about the truck , awesome!

 

Yes the internal cab flaps are working fine, I can direct air through the floor or the vents or the window.
I also pulled the dash and inspected the 7 vacuum lines, they appear solid and all were still holding pressure.

Closest I could narrow it down was the accumulator (dryer/receiver), the clutch wouldn't
stay engaged years ago when I got the truck so I hotwired the switch and someone told
me this would result in eventual accumulator failure...

Seeing how it's only 50 bucks I'm going to get one tomorrow, eliminate that as a potential source.

Well it really shouldn't matter because all air conditioning systems consist of the same parts,
the lines go from the compressor > condenser > accumulator > evaporator, and back to the compressor,
if I'm not mistaken, in that order.
There's only 1 or 2 other parts, some kind of a valve, and then the switches in the cab, fuses and relays.
Oh, and it's a PAG oil system running R134-A but again none of this is really relevant.

But to alleviate the concerns it's a 2nd generation RAM meaning that most
everything is interchangeable on these anyhow, 1995 D-2500 SLT 5.9L

Here's a diagram of a system, it applies to MOST automotive air conditioning systems:
(Oddly enough on our trucks the dryer is PAST the evaporator, but I don't think it matters)

 

So it was working with the jumper wire on the switch until now? The reason it would not stay engaged originally is because it was low on 134a, forcing it to run when low could also cause damage to the compressor.

And maybe the orifice tube is clogged.

 

Yes but even when the system was properly charged the compressor would cycle, the only
way it stayed running was jumped, I ran it like that for 2 years.
And yes I suppose I could hook up the gauges to see if the pressure builds in an abnormal manner...
Because the other possibility is a clog, but either way I'm going to have to take the vacuum pump to it, more than likely pull it apart.

Which is the orifice tube?

 

It's in the liquid line between the condenser outlet and the evaporator inlet . It is part of the line and the whole line needs to be replaced to replace it.

 

Sorry, on a 95 the orifice tube is replaceable without buying the whole line. See,info about the truck DOES matter,

 

I think I saw in my Haynes Manual that the Orifice tube is in line outside by the Condenser. Right were the connection is in front of the radiator. If you do take that apart be sure to post & let us know how that goes. I may be looking into opening mine up also. Mine seems to work fine as long as I keep it on LOW. If I set it to MAX then it slowly starts to loose cool. I'm thinking maybe an Orifice clog on mine. I have to get some good gauges first and see what is going on before I formulate a plan of attack.

 

All right, here's the latest...
Got the new accumulator (aka dryer/receiver), removed the old...
And while that was out of the way tried forcing a little compressed air
down the OUT line in the firewall so as to back flush it.
Unfortunately I couldn't get a really good seal so I didn't get a lot of pressure...
But I also couldn't get much of anything to go through...
Out came a couple of drops of what looked to be rusty water, that was about it.

I'm guessing there's a clog down in that way somewhere, in the evaporator itself or one
of the lines leading to or out of it...

I'm wondering if there's a way to force some kind of air or refrigerant through the system backwards,
how to hold the pressure and keep it from going the other way...