The amount of drop, inlet temperature vs outflow, depends greatly on blower speed setting. If you had the blower cranked all the way up 30F differential is a respectable #.

I think PO said doors were open.
Dave

The only valid way to measure the vent them is to roll up the windows and go for a drive. Sitting in my garage my AC never gets real cold. Get out in real world driving situations and measure the vent temp. Fan running at MAX, you should get 40 to 50 degrees even in 100 degrees heat.

When we charge & test vehicle systems, the doors are closed, windows are up, the heater off, the fresh air vents closed, otherwise you will never know the final performance or delta.

On the other side of the industry, HVAC for homes, commercial or industry... can you imagine a tech trying to charge by P&T and all the windows are open? lmao, he will be there for days!

Unless your real world driving involves stop and go rush hour traffic.... :):):)

Vent temps even lower than 40 degrees are achievable in a 911 being operated in the above conditions with high 90s ambient. - no trianary switch manipulating condenser fans or supplemental engine bay fan required to get there, either. And yes, with the evaporator fan set on max. ;)

Totally agree - those who recommend charging with windows open, etc. are not thinking straight.

Yep.

May I say that I fail to understand..?

With the windows/doors open the system inlet airflow will not vary with time, providing a temperature reference CONSTANT throughout the charging procedure.

With the car closed up the temperature "reference" will be declining, possibly rapidly, and thus only the high side pressure will be affected by OAT.

It is my understanding that in order to properly charge using pressures, low side pressure, the TXV must be WIDE open...

Enlighten me..?

I think there may be confusion about charging by weight, and charging by P & T. On most a/c service jobs, the system is factory defined and the charge amount is specified. An automatic machine evacuates and charges by weight. This goes faster with max heat loading, thus doors/windows open. When charging by P & T, the conditions simulating actual use allow evaluation of pressures at outside ambient temperatures, and measurement of applicable vent temps.
At least that is my understanding.
Dave

TXV is controlled by its sensing bulb.
And, yes. You failed to understand what you posted.

I was also under the impression that doors/ windows open was the best way to load the evaporator/ TXV and get the correct P/T for checking. Of course, as I said, I am a novice at AC charging. What are the correct high side/ low side pressures for 100F ambient?

A chart with this data was with my gauges:
http://forums.pelicanparts.com/uploa...1408397547.jpg
I guess I am lucky I ran out of R134 before getting to 300#!!!

Lastly, what is the drier sightglass supposed to look like? Full or not?

I will check pressures again tonight and run it with the windows closed to see what temps I get to.

Well, if you are in Texas and its 100F outside when you start charging, if the windows are closed before you charge it will be 130F in a few minutes, give it an hour and it will be much higher. Let it sit in the sun with the windows up and every piece of 'matter' (seats, steel, etc.) inside that tub is gonna be soaked to the bone in "heat". So, if you open those windows, and try to charge the way you thought you should charge, logically, you are not doing it the right way, lol.

Look, NOBODY, besides you know who, drives around with windows down and the AC on, an tries to charge a system based on P&T or estimated volume with windows down.

100F, R134a, in a perfect world with a stock 911, go for 276 max. R12 is 240

Actually, "you know who" has revealed in another current a/c thread that he does not do any a/c charging, period - pays shops for that service and to do simple tasks like r134a conversions. Whoda thunk it based on his years of all-knowing, a/c pontification!

Well, you knew that.
And Walmart is having a sale on RedDotTrinarySwitches

Scotty Kilmer says windows open. See 1:20 in. Just sayin'

https://www.youtube.com/watch?v=80jSH8VQZms

^^^ Bob, is it possible that "Scotty Kilmer" is wwest's pseudonym?

I like Scotty. He makes sense. However, just sayin'.

I have not absorbed this thread deeply enough because I am still reeling from the R/D dent mishap.

I decided to start over and had the system evacuated. It has been on the vacuum pump since last night and I plan to recharge after work. It is expected to be 85-90F and 60% humiduty this eveing. What should I target for pressures and vent temps?

Thanks in advance.

P

All of us who have actually read what he has written over the years. He has "internet expert" written all over him.

At first, I thought he was a clever troll, but then found out he actually believes the fertilizer he's shoveling. Which makes it even more sad. Well, that and the weird conditions he sets up for what constitutes a functional aircooled AC system. Change the interior color??? Tint the windows??? 75 degrees is plenty cool enough??? Seriously? If you take the money you spend changing the interior color and tinting the windows, you can buy a whole pile of stuff from Griff, a nice vacuum pump, and a set of gauges. And do better than 75 degrees, LOL. And not ruin the value of your classic sports car by pimpin' it and changing the color of the interior from the one on the sticker.

In addition, the fact that you would have a working AC system means that the value of your car goes UP, because now you could sell to a wider market. By my estimate, buying stuff from Griff could return 70 cents on the dollar, which is a heck of a lot better than just about any other modification you can do.