Does anyone see anything troubling about these numbers? Will the low side drop once fully charged?

Nathan, interesting that there is no groove, as like I mentioned, no groove means an o-ring will not work.

The best place to check for a right sized copper washer would be at an auto parts or motorcycle store. I'm refering to washers that are used to seal brake caliper banjo fittings and so forth - a lot more pressure than the a/c system produces. But that said, a hardware store with a good fastener selection might have them, too.

And regarding the above numbers, put them out of your mind as they are meaningless since you did not have air blowing over the rear condenser.

Also, is there a consensus on the doors open vs closed? Seems like if your vent temp measurement are to be comparable from one moment to another you need to keep cabin temp constant, otherwise you're introducing a lot more variables than just cooling rate in the Evap coil and you would need to subtract out the ever changing cabin temp.

^^^

Doors closed and windows up for me, as I am trying to establish "real world" conditions when I charge the system.

Griff recommends this technique as well.

I can't say thanks enough...this whole project would hAve been inconceivable with your's and everyone who has posted useful info on this over the years.

Fwiw, I was encouraged by the ~30 F delta T across the coil... I think that's close to "as good as it gets" right?

No problem - am glad to help (along with the barb slinging, buttofcourse)! :)

30F evaporator coil temps = excellent, in high ambient heat environment!

Your local NAPA, AutoZone etc. (or even WalMart?) will have copper &/or aluminum oil drain washer assortments - something from one of those might fit.

I just ran to OReilly and everything they had was too big. Will check Napa tomorrow. Wonder if alumininum will work? Found that at HD.

^^^ Aluminum would be fine - I've seen probably has many brake banjo seal washers made of aluminum as I have made of copper.

You'll have to use your own judgement about the "tightness", obviously, but don't be shy with it (BUTT not so tight that you pull the threads out, of course). :D

Today I took apart the errant service port adapter and discovered there was a groove for an o ring on the adapter side, though very slim. I refitted the pressure switch and managed to screw the thing together without the ring squishing out.


http://forums.pelicanparts.com/uploa...1437688077.jpg
http://forums.pelicanparts.com/uploa...1437688095.jpg

Then I vacuumed out the system for another 3.5 hours. Then started charging. This time I closed the deck lid with a towel to protect gauge hoses and had box fan pointed at the car.

Starting OAT = 81F
78 psi static charge.
Hi P= 252
Lo P = 26

I added 42.2 oz R134a

Vent T w. Window and sun roof open = 46F

Temps were still falling and the cabin felt pretty chilly so decided to go for a drive. Carved some turns on my favorite neighborhood twisty.

Vent T w cabin closed and tooling around town =

http://forums.pelicanparts.com/uploa...1437688551.jpg

While happy with the results, I'm wondering if I added too much freon?

And by the way, the Kuehl Evap blower fan really works well. Each of the fan speeds produced noticeable airflow, with stock resistor pack fan control setup. The max setting was very robust.

Very nice. What RPM are your pressure readings taken at?
Dave

Idle.

http://forums.pelicanparts.com/support/smileys/wat6.gif

Had a couple of Moose Drools after work with fellow Carrera owner Jamie and thought of you.

So, are you more or less finished?

May need to let some out.

Also, I seem to have developed a fuel leak on the right side of the engine!

Overcharged, maybe.

In a perfect world, at idle:
R12 at 81F running, high side target would be 194.4 psi.
For R134a it would be close to that of R12, say 204 psi

If overcharged, why is the low side pressure only 26 PSI?
Thanks,
Dave

Just because a system is 'overcharged' does not mean the low side will rise proportionally.

Thanks, Griff. I barely understand this stuff on a good day. When I charge my system, both the high and low pressures rise together. It seems in the past when I have overcharged it, the low side pressure would go up into the 40-45 PSI range. I am not arguing, I just wish I understood.
Dave

If it is of any help, my Retroaire system takes about 18 - 20 oz to get pressures in the range....

Dennis

I use twice ambient (F) +30 FOR R12 and twice F +50 for R134a for ballpark high range. This is meaningless (I think?) as it's not really the topic and I don't mess with (yet) other than regular cars - factory stock.

I do have one question - this is full-on noob ignorance. To assess the low side pressure, is the blue valve turned off to negate the 70 or so lbs pressure from the 30 lb tank?

Nathan, looking good, and yes, I would consider your pressure a bit high for the ambient conditions (I would defer to Griff for anything on that subject, however).

Bob, yes, you have to stop the flow of refrigerant from the tank/bottle to get an accurate, lowside pressure reading - the number is way different with the tap open versus closed.

Nathan, looks like you got some cold!
Enjoy it and if it were a bit over so what, it can't be that far off optimal. IMO
Even if you wanted to take some out how would you measure it?


Dennis, I put 22oz and have vents of 39F in my Retro system, when I went to 24 oz the temp went to 41. Thats with the stock front blower and condenser. But I dont know what it would be with the 20 oz you say, you got any numbers?

http://forums.pelicanparts.com/uploa...1437768383.jpg


http://forums.pelicanparts.com/uploa...1437768417.jpg

Just did mine, low pressure was 45, high was 240....temperature at vent after a short drive was 40F. Ambient 85 degrees.

Total put in was 20 oz as per can weight, I suspect I have about 19 oz in the system what with leakage/stuff in hose etc.

Dennis

Just for the sake of comparison, and possibly added confusion :D, at about 92-95 ambient, I had 30 lowside, 220 highside and vent temp of 27-28 degrees. This was when I re-charged about two weeks ago. I got the same results when I charged in almost identical temps last summer.

How much did put in Ronnie?

George, no idea on the amount of refrigerant - I didn't weigh the tank. I've never charged any vehicle via weight/amount of refrigerant (never even look that info up), but just use the vent temp + pressures method. I'm not saying that is how it should be done, but it's always worked for me.

Ronnie, do you use Griff's formula for your pressures based on ambient T?

The problem with vent temps as a yardstick is, as you cabin cools off, the vent temp falls whether your ac is cooling it more, or less. And what if some other variable changes?

I'm sure Griff has a good reason for doing it this way. You could ask him directly...

That's been my question, concern, ever since I came across this closed cabin topping off procedure.

Chasing a moving target, it seems to me.

Absent: charge, measure, turn off A/C, wait for IAT to rise back to OAT, repeat ad infinitum...

Sort of, but the thing is, I don't think I've ever charged a system when the temps are below mid 90s, (are that way around here from the end of May to well into October), so I'm usually always shooting for about the same pressures whenever I charge.

And regarding the vent temp yardstick - I always try to determine what is the lowest vent temperature the system is capable of delivering (takes experimentation & experience, obviously) and try to synchronize that with the pressures I am looking for - no changing variables that way, as far as I see it, buttofcourse (that's for Bob, buttofcourse). :)

Also, Griff explained to me behind the scenes why it is a good idea to record refrigerant weight/amounts added - good reference and troubleshooting data to have for future charging - so I will do that from this point forward.

Check for that on top of your noggin.

I'll bet it's sharp as a pin.

Let's see.....like a .........pin head. Kinda catchy.

Ronnie is a pinhead. Yeah. Heh heh. A pinhead.

That "moving target" business is not how it works.

In order to see the coldest temps the system is capable to delivering, the cabin air has to be cooled (the evaporator's incoming air) via re-circulation mode - that does not take as long as you would think if the vehicle is in the shade and has not been pre-heat soaked when you are charging. Once the coldest possible temps are reached, (the thermostat comes in to play here), you note the pressures and verify that they are in your target range - if they are, then you can consider it a success, and if they are not, it's time to start troubleshooting.

Check your phone for pics to verify or rebuke yer "pin-head" theory. I advise caution regarding who is around when you view said pics, however!

"I'm sure Griff has a good reason.."

I thought you to be the expert in these matters.

But, a theory, if I may...

Orifice tube systems have very narrow range of refrigerant charge. With the charge just a tad low and the evaporator tends to freeze up.

TXV systems, on the other hand, due to having evaporator "condition" feedback, have a much wider range of fill levels for which they will maintain control and prevent the evaporator "charge" from reaching the freeze up zone.

But, as Charlie suggests, what if you ever so slowly charge the system just barely short of the charge level wherein the TXV is in its range of control? You then have successfully "simulated" an orifice tube system with a low refrigerant charge.

Eureka! You now have a system with the lowest possible vent temperatures.

But with a strong tendency to freeze up.

But, shouldn't the thermostatic capillary control switch prevent that?

Not if you calibrate it in accordance with Charlie's "seeming" parameters.

I can't be certain but it appears to me that Charlie's set points for the capillary sensor thermostatic switch will put the average evaporator temperature in the sub-freezing zone.

How else do you get our systems to produce sub-freezing vent outflow absent somehow over-riding BOTH control aspects..??

How do you prevent freeze ups? Pay close attention to the vent outflow air volume, or live in a very dry climate.

Eric can speak for himself, and will correct me if I'm mistaken, but I don't think I have ever seen him post about doing a/c charging, and unlike you, he does not have a track record of posting about subjects that he does not have actual experience with.

On the other hand many orifice systems use a thermostatic capillary switch for control and all of those appear to be subject to freeze with a sub-standard charge level.

Perhaps Charlie, by charging "just so", has figured out a method to simulate an orifice tube system. TXV outside its range of control, capillary thermostat system not capable of detecting freeze up onset.

Any other theories as to how Charlie's method gets you su-freezing vent temperature my ears are wide open.