I teach those classes, Bro!!!

Will do (for now :)).

Understood, and I admit that not much actually gets me genuinely riled up (can probably thank 16 years of teaching 8th graders for that personality development), but I do see, understand and appreciate the damage that West does. I guess I tend to think of his behavior in terms of an overly annoying gnat that is semi-fun to swat at for a while rather than something worth getting angry over. Butt I do understand and respect yours and Bob's points (not THOSE points)!

Besides, the lowest, high temp in the local, seven day forecast is 104, with Sunday's and Monday's highs predicted to be 106 (lows all week in the mid-80s); dat's gotta take a tole on the ole' noggin, right?!?!

Why the long rant when a link (or more?) would suffice?

You are a veteran here, you can operate the search function if you choose. If you're really interested in an answer and have lost the ability to search, start an new thread.

I just spent the better part of 3 hours searching...

"evaporator + freeze"

"evaporator + ice"

Some responses go all the way back to 1999.

All I have found so far is suggested or methods used to prevent freeze up of evaporator is inadvertently or intentionally operating sub-32dF....

1. Turn the cooling down..

2. Recalibrate the thermostat.

3. Change the thermostat's hysteresis (on/off span)

4. clean/burnish the capillary tube.

5. Makes sure the capillary tube is in contact, actual or some medium, with the brass sleeve.

6. Make sure the brass sleeve is in....

7. Relocate the capillary tube.

One thread stands out as most needing an answer...

http://forums.pelicanparts.com/porsche-911-technical-forum/858116-c-reverse-gases-early-model-911s.html

^^^

Why not put that gobble-de-gook in the thread YOU created on that very subject, rather than in Nathan's thread on his a/c system upgrades?

http://forums.pelicanparts.com/porsche-911-technical-forum/837717-sub-freezing-vent-temps-how.html

Amen. I even asked him to start his own thread a few pages ago.

Status update on my project. I sprung a fuel line leak while making my victory lap, new hose ordered from or host, due in on Monday. Once every thing is put back together I will check pressure, and perhaps reduce some of the charge using CG's recommended hi side pressure calculations.

With any luck, I will be able to run a track day at ORP on the 16th, and be cool as a cucumber on the drive over.

Been down with pneumonia, so was not able to check until today. Took the car for a nice drive, outside air temperature around 75F, after about 15 minutes of driving, vent temperature was around 34f, maybe even a degree or two less. I was not able to take a picture as I was driving at the time.

System is all RetroAire as I have stated before.

Dennis

Update.

After working well for several weeks, including the aforementioned long road trip to ORP, today my system pooped out. Driving home w. OAT ~95F, I might have been getting 75F vent temps.

A few hours later w. Car finally in garage, was able to throw my gauges on. W. 85f OAT, was able to get vent temp ~72.

Static pressure ~90 psi, engine was hot. I let a little freon out until high side approximated Charlie's formula value, 215 psi

http://forums.pelicanparts.com/uploa...1440560479.jpg

Airflow from cabin vents was good. All the condenser fans seemed to be operating.

Suction line connection to compressor was not cold.

When I have time, I'm going to pull up the floor board to see if the underside of the evaporator is clogged. That's all I can think of at this point.

Any thoughts?

Pressures look great. What the hell?

No way you picked up a giant flying squirrel that attached to the bottom of you evap within one road trip.

Stumped.

Let's assume, for discussion, your evap froze solid, for grins. How much time between driving and pressure testing occurred?

Agreed with Bro Bobasaurusrex, pressures look more or less perfect. Hard to explain the poor vent temperatures and a plugged evaporator doesn't seem likely since the vent airflow is strong - really strange.

Just to clarify, the pressures in the above pic are with the compressor clutch engaged and the compressor running, correct (not static pressure)? And if so, is the engine lid down?

Assuming your observation was made when the system was operating (thermostat CW, fan speed switch on), and the system has not lost refrigerant, and the gauge pressures you posted are during that time frame.

1) With the system 'operating' go to your smugglers box. Inspect the evaporator outlet pipe. Is it frozen, sweating or warm. Inspect the expansion valve inlet hose fitting, is it cold, cool or warm.
2) If you have a digital thermometer with a decent length probe, drill a small hole for it in the top of the evaporator box near the thermostat's probe, preferably drill this hole closer to the evaporator blower motor's plastic vertical housing or toward the rear of the box near heading toward the windshield (anywhere away from the probe but where there is a sufficient area of evaporator cooling fins for it to be inserted into), and take a temperature reading of the evaporator coil when the system is operating.

Yesterday was filled with scheduled fun so I didn't get to think or do anything related to this issue.

After I provide some clarification, I'm off to the garage to investigate further.

I started my drive with the car pretty hot and the AC never even got cool. I was not able to check things out until about three hours after the event. Btw, relative humidity at my location was probably less than 20%

Yes, the compressor was running and the deck lid was closed when I observed the pressures posted above. Yes, gauge picture was at that time.

Personally my bet is on the flying squirrel, or, in this case, crappy foam insulation I used on the outside of the evaporator box. Who knows, we'll see.

To get into the smugglers box, I have to disconnect an amp, which is a PITA. May not have time for that tonight, but will over the weekend.

Question, what if I inserted a thermometer probe into the capillary tube hole (after removing said tube) ? Don't have a skinny enough probe but might be able to borrow one.

Thanks everyone.

Nathan

Report:

No flying squirrels. Bottom of Evaporator was fine.

Before yanking amp, went for test drive. Fan speed = 4, thermostat fully CW. Amb. T = 83. In the first 3 blocks vent T dropped to 72.
I lowered fan speed to 3 and vent temp dropped to 68.
Turned fan back up to 4 and vent temp went up to 72 and kept rising to 75
Pulled into garage and turned fan speed to 2 (lowest on speed) and temp dropped to 58.
Shut off car, spent 10 minutes pulling amp and opening smugglers box.
Turned car back on for a few minutes. Evap outlet line cool, not cold.

Could the the txv be not working right? I still have the original Evap and txv assy sitting on the bench, could reinstall this weekend.

While testing in Tuesday night, the compressor ran the whole time as far as I noticed

I'll try the temp probe insertion tomorrow night

As I speculated in post 228, I did in fact drive to ORP and back on the 16 and the 17 th. AC worked well for the 5 hour drive. The last couple hours on the way out I was driving into the sun and had to toggle between max fan and medium (settings 4 and 3) to stay comfy. On The way back, settings 2 and 3 were adequate

ORP was a blast, btw. Highly recommended for you in the PNW.