Wow! Dug this up...bad case of Dejavu, have been vacuuming the system for several days off and on. Seems to hold vacuum but as I mentioned in another thread my new yellow jacket gauges never go below 26 but their "zero" setting is a white space about 3-4 degrees in width so maybe that is the issue. My old harbor freight gauges show I'm down to 30 and it holds there for hours. Did purge process on lines and added two 12 oz cans r134...never dropped below about 70 degrees and pressure 50! And 350. With 24 oz! About ready to fire a .45 round through this system. Thank goodness my RDX will freeze my butt off. Keep in mind this is a new compressor, new hoses, and thoroughly cleaned condensers, and brand new evaporator. I give up...

Is the evaporator outlet pipe Frosty or sweating?

Buck, it seems like there must be something simple that you've overlooked (easy to do, buttofcourse) - your vent temps, and pressures are way to high (as you know). I think I recall that you have almost the same components that I do, and with ambient temps like we had today, you should be able to see vent temps in the high 20s-low 30s, with highside pressure of around 220 and lowside of around 30 (idle engine speed, windows up, fan speed and thermostat on max settings).

Are you charging with the engine lid down?

Is it possible that you have an obstruction in the system - such as a plug accidentally left in the expansion valve fittings or hose or condenser fittings (like aluminum foil or rubber plug or something)? It happens!

Agree, there's definitely something wrong...however I'll definitely check the evaporator outlet to make sure it's cold. I have not inserted the temp probe into the evaporator core but will do that tomorrow. I'm going to review everything to see if I've done something seriously wrong...which seems to be the case. The performance is so out of line with expectations something has to be seriously wrong.

Fired ac up again to check Kuehl's suggestion. This is basically a repeat of last year...if I put a temp probe into the airbox its showing about 59 degrees for the core/evaporator. When I started the car, lid almost completely closed it quickly went to 25/250 then over about 5-10 minutes goes to 50/325 at idle. The outlet of the evaporator is extremely cold to the touch but not "icey". Is there any chance this could be caused by hooking the r/d up backwards? I recall there was no marking such is "in/out" so I just hooked it up as I recall the other one being set up. I'm beginning to think its something other than a little air in the system since I was very careful with the process and I've done it several times now.

Buck, I don't know what to make of your radically changing gauge readings, but I'm sure Griff will have some good suggestions.

As far as the dryer connections - the top fitting is for the hose from the evaporator and the bottom fitting is for the hose from the nose condenser.

+1

My call is replace the expansion valve.

I have seen (I have mentioned before) 425psi on the high side on an 89 930 garage queen - at idle. Plugged X valve.

Call Charlie Griffith. Seriously, piss a wee bit of money in the right direction.

The dude is very approachable.

911/930 Expansion Valves (TEV, TXV) seldom "fail" on their own, mechanically.

Things that make a TEV to appear to fail are:

1) Debris in the system. This could be residual trash from a compressor that locked up.
Or, 'jelly refrigerant oil'. We had a car in our facility years ago we named the car from hell. The client was a gentleman however he insisted we use his old Sanden compressor; which very old. We had erratic gauge readings, inconsistent. When we explored what was in the system it appeared to look like a glob of wax reminiscent of a lava lamp from the 70's; less the strobe affect and smell in the air. The glob was wax'd mineral oil left over from the R12 system. The solution was to AC liquid flush the condensers, hoses, remove TEV from evap and flush, new drier, new compressor.

2) Moisture in the system. When water moves into the TEV it can freeze and either cause the TEV to stay partially closed (low low side pressures) or stay open (high low side pressures).

Can an old TEV or a new one fail mechanically on its own. Yes. It is possible however statistically not often. So when someone decides to swap out the questionable TEV with a new one and suddenly the issue disappears .... you have to ask:
A) Was it the TEV, or
B) Was it moisture or debris.
It comes down to dollars and sense. If you add up the time to properly evacuate, charge and test vs. the cost of tossing another TEV and drier at the system, sometimes its less costly to do that. On the other hand some of us like to know what really caused the problem for situations where we come across it again.

When we pull a vacuum on a system the first procedure is to test our equipment.
This means testing the capability of the pump to pull down. Next the integrity of the service set: service hoses not on the car, will the service set allow us to pull down a decent vacuum. If all looks good then you move on to car. 2 weeks ago we 2 issues confront us. First our old faithful vacuum pump decided to retire, so a couple hundred bucks bought a brand new pump. Next, our old faithful digital manifold tried to convince us that its high side gauge wanted to be above the rest; it read 13 psi when open to ambient. So, several hundred bucks again. All this to fix one client's car that needed to get done ASAP.

How good of a vacuum is good. Well, most digital manifold gauges today will tell you on a perfect day they are either -29.75" or maybe -30". But that is rough scale in mercury. You need a 'micron' gauge to tell where you are really at and where you put it is critical. If you attach a typical micron gauge on a new pump adjacent to its service connection you might get a reading ranging from 75 to 200 microns depending upon the day. If you move that micron sensor up to your service set it could read 200 to 300 microns. And if you put a service valve port up by the front condenser it could read 500 to 750. It all depends upon the distance from the pump source, and the attitude of your pump, ambient air temp and humidity.

So, in the case of what 88911coupe is facing, after I ran through all the Pre-Flight checks of equipment, I'd remove the TEV, toss in a new drier (because the time and costs are running up), and properly pull another vacuum and charge by pressure & temperatures as well as monitor the weight of refrigerant: and writing everything down along the way because a few Tanguery's the night before and constant phone calls and emails can really screw up your game.

OK...possibly I missed something obvious...in this pic should I have both "sensors" covered with presstite? The inlet hose gets pretty cold and the outlet is cold as well. Sort of grasping at straws to find out why the pressures seem to get overly high even with a minimal charge of R134. As Charlie says I may have air in the system but I"ve been very careful and can't figure out where it would be coming in from. Just wanted to check and see if that other connection needs to be insulated or not. Hard to see but the pigtail is covered.http://forums.pelicanparts.com/uploa...1469834767.jpg

Thanks, I had the vacuum on it for some time...maybe didn't get it all out. Thanks Griff. I was somewhat confused seeing those pressure with a "relatively" small r134 charge. I'll re do it and hopefully have better results.http://yeahonlinemarketing.com/apple/images/48.gifhttp://yeahonlinemarketing.com/apple/images/6.gif
http://yeahonlinemarketing.com/apple/images/4.gif

The only component of the TEV (expansion valve) that needs to covered with Prestite insulation (black) tape is 'pig tail' sensor that exits the top of the TEV and attaches to the top of the evaporator outlet tube, secured with the metal clip. The pig tail sensor tube contains a refrigerant gas which expands and contracts with the temperature of the evaporator outlet; the gas pushes a bellow in the TEV which pushes a pin in the TEV which throttles the refrigerant flow based upon evaporator outlet temperature.

And you will want to cover the gaps in the top of the evaporator box where the evaporator outlet tube and TEV inlet tube exits the box; to reduce outside air entering the box.

Your TEV inlet hose fitting should be WARM to HOT, while the evaporator outlet should be COLD. If your TEV inlet hose fitting is cool this means you have blockage which forms an orifice somewhere south of the TEV inlet; the liquid refrigerant is expanding or changing state from a liquid to a gas, this usually happens when there is moisture (ice) or debris in the system.

Ok thanks, was hoping I found the problem. Just to clarify, the TEV body is cold, the metal pipe into the TEV is hot. I have a temp sensor and the body of the TEV is about 49 degrees, creeps into low 50s after a few minutes.. There's a tiny hole in the evaporator box that I can insert the temp probe into and get a reading on the core which is the 60's. Vent temps only getting down to mid 70s. Considering all hoses, compressor, evaporator are new, in addition to a new/additional condenser with a fan I don't know what I've done wrong....obviously something. I don't think its air in the system since I've beeb so careful when I recharged but maybe time to let a "professional" do the vacuum and recharge.

An 88 with a stock system running R134a typically uses 39-41 oz.

You have a 3 condenser system? and with 24 oz your pressures are 40% or more higher than what they should be. That typically is a sign of air in the system because your 40% undercharged.

If you pulled the perfect vacuum and all the system components are functioning as they should be, that's a sign of air unless you can rule out something else (condenser function, contaminated refrigerant, a blockage in the system ).

OK...another desperate attempts to resolve this crappy ac. I stumbled across some AC website that says the clamp holding the sensor bulb MUST be metal and the more heat conductive the better. I was using a a plastic tie wrap which is said NOT to use. Now replaced it with a metal clamp and will vacuum again and see what happens. Just curious...what would happen if the sensor bulb is not insulated? Only for a test. Wouldn't that cause TOO much coolant to flow and possibly freeze up? I WISH that was the problem I was having!

The sensing bulb 'throttles' the refrigerant flow.
The sensing bulb is suppose to 'see' temperature of the
evaporator outlet gases. If you don't have it well insulated
with Prestite tape (or your favorite color of PlayDo or Sillyputty) it will
see the ambient air temps in the Smuggler's Box Well; hence if the
sensing bulb is seeing warm all the time it will tell the TEV to keep dumping refrigerant in the core.

About TEV's

Do you have a "bad" TEV, maybe (anything is possible), however simply based on
your noted amount of refrigerant and pressures I would not go down that road yet.