94 suburban a/c problems w/dual air

Anybody got a diagram of the a/c system for a 94 chevy suburban? Just serviced the system; low and high press. is good, no leaks but 83 degree air is all I can get out of the front and rear vents. The line going into the front evaporator is warm and the line coming out of the evaporator to the accumulator is warm as is the low press line going to to compressor. I can't imagine both evaporators are clogged. I seen a post on someone elses problem where someone suggested the filter up by the condensor. By looking at the lines I can't pick out where this filter might be. Any and all help is appreciated. Also, does this system use an inline orifice? if so, what's the access to it?

And those good high and low pressures would be what at idle and

low press 35psi high press just over 200psi with front & rear running. digital thermometer in vent in front 86 and in vent in back 83.

at idle speed. low press 35-40 high press @ 200psi. thanks

snipped-for-privacy@bellsouth.net wrote in news:1184880633.986905.11040@

thinking.............

snipped-for-privacy@bellsouth.net wrote in news:1184880633.986905.11040@

what refrig. are you using? 134 or 12?............orfice tube is located between cond. and evap. (under hood) just before high side enters evap. case. you will notice a bulge in high side line just after the orfice tube service joint.............kjun

Okay, no pressures at 2500 RPM...

Is the inlet (pipe)to the front evaporator cold?

Is the outlet (pipe) from the front evaporator cold?

The front evaporator uses an orifice tube, it also is the screen (filter) mentioned in your original post. If it were plugged, the low side pressure would go way down when the compressor speed is increased. The location of the orifice tube varies, it will either be at the nut connection at the condenser outlet or at the nut connection at the evaporator inlet. AFAIK, the rear evaporator uses an expansion valve (TXV).

Ok. Low press 40, high press 200. Front and rear air on fans on high.

Thanks, located and replaced orifice tube. Is there one for the rear evaporator?

Front evaporator inlet line warm, outlet line warm. Accumulator warm. Located and replaced front orifice tube, system evac. and reserviced but same results.

Indicates to me that there is no refrigerant present at the evaporator inlet. You either don't have enough refrigerant (unlikely given the low side pressure), too much oil, too much air (any air is too much), moisture blocking flow or the wrong refrigerant.

What is your refrigerant source? Are you using pure 100% unadulterated R-134? How are you evacuating the system? How are you measuring the charge when re-filling? Has sealer or O-ring conditioner ever been introduced into the system? If you believe the answer is no, have you verified this? Have you verified the amount of oil in the system? Does/did the orifice tube fit the line snugly when you installed the new one? How fresh is the accumulator (desiccant)?

Ok, 134a 100% unaltered. useing vaccum pump getting down to 25 inches. When charging, using set of guages. I've owned truck since 2000 and I've never used sealer or cond. Unfamiliar about checking oil in system. Orifice tube fit snug. The old one had debris on the screen. The accumulator is original and I had thought about replaceing it but I don't like loading the shotgun and throwing parts at something. I appreciate your help. Hope i answered all ?'s.

Nowhere near enough vacuum. Not even close. Nada. Zip. Zilch.

So, I take it this means you have no way of actually measuring the refrigerant by weight. There should be a sticker underhood that specifies X lbs-X ounces. There is a reason for that.

Okay, that's at least one thing positive.

Simple. If there is any suspicion about the oil quantity like loss from a leak or there having been any added via cans of refrigerant/oil mix, the system needs to be flushed and the proper quantity of oil added to each component.

That's good

Well, there shouldn't be debris on the screen. It came from something somewhere that is disintegrating. Are you certain that the replacement orifice tube was the correct one for R-134?

It should be replaced any time the system is opened, like when you changed the orifice tube. No exceptions.

I was using a set of guages. The max vaccum the guages will go to is

The reason that the vacuum gauge only goes to 30 inches is because 29.992 is the maximum (theoretical) vacuum achievable on earth.

Microns is a unit of measurement that can (for purposes of this discussion) be applied to pressures below atmospheric (vacuum). The industry standard for evacuating an automotive AC system is

You claim it's holding (rules out a leak) that leaves moisture. Honestly, at 25 in.hg. one really can't be sure either way.

Even though it's a popular belief that at XX vacuum, water will boil at X * temperature, boiling isn't necessarily removing.

Sounds like this system is highly contaminated.

I really appreciate all your help. I'm going to r & r the accumulator this am and go from there.