New serpentine ac system in car here is the link for those that are unfamiliar.

http://www.montecarloss.com/community/ubbthreads.php?ubb=showflat&Number=1073271#Post1073271

Ac system
Sanden 4864 flx7
89-92 camaro Original Air condenser 11-215p
89-92 camaro Original Air liquid line 13-281
89-92 camaro four seasons soft hoses 55451
Four seasons 38904 variable orfice tube
88 Monte Carlo Gm 151589 accumulator
88 Monte Carlo oe evaporator

As seen by the parts list my car pretty much has a 89-92 camaro ac system. Two differences is the Monte accumulator which I compared side to side with the camaro accumulator, same size different location of inlet and outlet . Other difference is the Monte evaporator, not sure how it compares in size to the camaro evaporator.

Stock 89-92 camaro holds 36 Oz. Of r12, 80% r134a charge should be 28.8 oz. I overshot a little and put 29.5 Oz of r134a in the system but I probably did lose some from bleeding air out of yellow charge hose. Probably not the best time to try tuning my ac but with long work hours you do it when time permits.
-73°
-52% relative humidity
- static pressure 72 psi
- ac on max
- blower on high
- 1200 r.p.m.
- radiator fans still running off low pressure switch
- fan in front of car blowing through grill

Here is what the gauges looked like under those conditions.

https://youtu.be/2Lqq4QGqcB4

Suction Line Temp - Gauge Temp = Superheat
Gauge Temp - Discharge Line Temp = Subcool

I borrowed a friends meter that reads ambient temp, relative humidity and has a temp pipe clamp. Where is the best place to read the suction and discharge line temps? What is opinions on the above video? What is ideal system setup (blower speed, state of ac controls, idle speed, doors opened or closed etc) when tuning the ac? When driving the car around 2000 r.p.m. center vent temp was between 47°-51° as compressor would cycle. Also as noted I'm using a variable orfice tube.

Quick note, your subcool is measures from the liquid line (after the condenser), not the discharge (that feeds the condenser). If it was me, I'd read the temps at the liquid line immediately before the orifice tube, then read suction temps switched between two places, the first is feeding the accumulator, and the second is the portion feeding the compressor. You can shoot for nearly zero superheat leaving the condenser, then make sure you have plenty feeding the compressor and you should be safe. Superheat is essentially performance left on the table in order to protect the compressor. Subcool is making sure that you have a good column of liquid feeding the metering device for consistent operation.

My gut on the video is that the charge is low, but given the mild conditions, I'm not sure exactly how low. You could disconnect the low pressure switch, jumper it, and see what pressure it wants to settle in to and do your adjusting from there. That should also get a stable discharge pressure, which I think ought to be more around 150 where the video shows it struggling to get around 125 before the low switch kicks it off. Speaking of low pressure switch, make sure you plan on adjusting it for the right cut out pressure for you, google says 21 psi for 143a but you might adjust it to your liking or experience. You want to give it enough so that you don't freeze the evaporator if for no other reason than you will have to wait for it all to melt again if you do, but if you're actively working it I don't think you will have much issue.

Are you using individual cans of refrigerant, or do you have a drum of it? Either is fine, just wondering how much flexibility you have on tweaking charge. Hooking up the hoses again is a lot simpler when you don't have to worry about breaking open another 12oz can to get 2-3 oz into the system.

Last thought, your setup sounds good, the fan in front is going to lower pressures a little, so if you are on the low side of "normal", I'd consider it fine. It will be more realistic for driving performance, but you might want to do at least on sanity check without the fan to make sure discharge pressures don't get too high, especially on a much hotter day. (It was 98° here in Texas yesterday, just run down here real quick and you'll have some nice AC testing weather ). Also, I keep my windows rolled down and/or doors open so that the car doesn't get too cool. The down side of running on Max is that you can start to affect your return temperature, the upside is that you aren't sucking engine heat from the cowl with the hood open.


When I ran R&D tests for stationary systems, the basic logic was to run a few charges at a range of operating conditions, inside and out, then choose the fattest charge that kept the system happy (to allow for some moderate leakage over time). Then you would run "Abnormals" at the worst extremes plausible, like a really hot exterior temp with a very light load inside, then a very heavy load inside with a mild exterior temp. The problem with automotive is that you have less access to the data and about 3 times the number of variables. You also have about 3 times the window of "Good enough" generally, so that's nice. But basically, I'd get a charge that seems to work for a good low pressure reading and good vent temps (probably reading you superheat at the evaporator and shooting for a small number there). Then make sure your subcool and superheat at the compressor are adequate, then remove your front fan, rev to ~2000 rpm on a warm day and make sure your pressure isn't in danger of tripping or relieving itself (I'm not sure what type of relief you have or what the high pressure cutout is on your system). Then run your fan at idle on a cool-ish day and make sure your low pressure cycling witch is adjusted right. That's fairly overkill, as most folks (shops included) would stop at step 1, but if you want to check it all out, that's what I'd suggest as a full battery of tests.

In case anyone is curious the r12 charge for the 89-92 camaro is 2.25 lbs and the charge decal on my 88 monte carlo calls for 3.25 lbs of r12.

Shawn, thank you for all the above information it's exactly what I was looking for. Hopefully towards the end of the week or weekend I will be able to get back with some numbers. When you say small number at evap for superheat what value would you think, 10 or less? This is my first dip into the ac world so I've been trying to study up a little on the internet which as you know the info can be good and bad. I'm using self sealing individual cans, luckily I have a couple extra so it's no big deal to add some if needed.

Probably 2° at the evap would be fine, basically enough to know that it isn't completely liquid at your "normal" operating range but close to it. The closer it is to the saturation temperature, the more liquid is pulling heat out of the evaporator. You would want something more like 10° at the compressor inlet to make sure that you don't have any liquid getting past the accumulator and into the compressor. Compressors are made for gas, not liquid, and don't appreciate being fed the wrong phase for too long. They will take it for a while, but it causes extra wear.

Probably worth focusing on the pressures mostly, and use the superheat to make sure it is safe long term. Your setup is not that far off of a factory configuration, just far enough that factory charge numbers can't be trusted. For any given evaporator condition (charge level and superheat), your subcool will be primarily a function of your orifice tube size. There's not a whole lot to tweak unless you are way off, then you will need to swap to a different orifice (which shouldn't be the case, you have a variable one already). But since you have a variable tube, you might not see much variation on the subcool anyway. Pressures and vent temperature should be your primary charge determination tools, evaporator superheat should be an indicator as well. the rest of them are sanity checks for longterm operation.

Think of it as a confirmation step rather than design step. If you were in an extreme environment or had a wildly different arrangement, then the subcool would tell you if you needed to increase or decrease the orifice size. In rooftops, we would set charge based on Superheat and evaporator performance, then see what the superheat was. If too low, we would reduce the orifice size, too high, open it up. And all of that was done at a controlled setting, such that we knew what was "enough" there that we shouldn't have issues at the extremes, then we go to those extremes and verify. But for auto systems, it's all an educated guess and the only outputs that generally matters is vent temps, system function, and owner satisfaction rather than energy efficiency, warranty, sound, manufacturability, cost, data centers in Dubai, snowy rooftops in Canada, and everything else.

An 82-92 Camaro has an accumulator, so the charge would be 90%, the filter/drier on earlier systems gets the 80%

Thank you for the tip Leo!

Just my experience. I have replaced my R-12 system with R-134. Everything I have is stock, but brand new from hoses to compressor. I needed new heater core, evaporator and condenser anyway. Followed the sticker that was on the car and calculate the amount needed for my newly setup A/C system (was it about 80% of R12 system? Forgot what was the calculation but I got the formula from here).

I first thought I overcharged it because compressor kept cycling. My gauges confirmed this. So took it to a friend who does the AC service and took out some 134 out. Thinking it's going to be OK, I just left that as is. Sure, when the compressor was engaged, it was nice and cool but it still was cycling. Thinking "what the hell. If I overcharge it again, I can take it back to my friend to take some 134 out again", so I charged the system again, but this time, I went by what the gauges read. It took almost a pound more than the calculation that I came up with.

To this day, system is working great (however, thinking of changing it to Sunden compressor and also change the condenser to more modern design ones) and haven't touch it other than tightening the belt once in a while. Same with my DD Lincoln. I had to change the compressor so went into AC shop (my friend wasn't available that time due to our schedule) to discharge the system, changed the compressor (which is whole another story by itself) and rechanrge the system. I first followed the repair manual, charge it but compressor kept cycling. added little more by reading the gauges and now it's trouble free.

BTW, I live in middle of the Pacific, so we rarely go below 80, and during the day is almost never.

Now that one Winter project is near completion need to revisit the one I left undone last Fall. After changing the compressor, electric fan controller, blower motor, suitcase door/linkage repairs and cleaning out the entire system again in late Oct outdoor temps dropped to the point it was pointless to try to get the charge dialed in on the near stock and still R12 A/C system.

Had the A/C on this week and was surprised to see the best I could do with dash vent temps was 50 degrees. So now it's time to reeducate myself on tuning this near stock system to try and get the dash temps back to what I consider normal for this car.

The original compressor died 20+ years ago and a thorough 134 changeover was done. Was never happy with that swap's performance, no condenser swap was done as parallels were just starting to come into vogue.
In 07 when the new engine went in the system was cleaned, new line set, accumulator, fresh mineral oil, and a high pressure switch added to the high pressure port to cycle the electric fans on system pressure, not the compressor clutch. After pulling a vac for hours a stock charge of R12 was weighed in and the system worked great for more than 10 years, sometimes see high 30s at the center dash vent.

Last year during the peak heat of the Summer, actually during an Autox event in June, the car overheated, the A/C faltered and what now appears as a bad diagnosis on my part as to what the failure was. That 20 year old compressor was replaced and everything freshened again. A failed connection at one of the electric fans was the cause of the ills but the refresh was already under way when that real problem was found. Yep, I'm human, stupid at times.

In the end a fresh charge of mineral oil and R12 was done and found i wasn't happy with the dash vent temps. OK, but not cold like when redone the first time. Education about how Superheat, Subcool , fixed orifice, and all the other silliness about automobile R12 systems got in the way along with the ambient temps dropping late in the year ended that misery.

Now need to revisit and finish this ice cube maker project and have cold toes at 70 when it's a 100 outside.
My primary focus will be tuning to see what a Superheat of 10 degrees at 85 ambient will net at the dash vents. This is a good starting point. Should be able to see in the area of 40 degrees dash vent to be happy with the system.

Ya know in the old days A/C was not important, most of my daily drivers didn't even have A/C. Not anymore, even the wife's car has heated seats i use occasionally in the Summer.
Bob

I figured I would put it here just as an update. I've had quite a few issues from my ac system and never could get it right. Pressures would be all over the place and never could get vent temps, temps, or pressure consistent. 2 times my compressor relieved the high pressure valve eating the paint off the valve covers, not good. Fans were on high both times. I just felt something was not right with the variable orfice tube. I had done a bit of messing around with the old r4 compressor setup with the fixed orfice and had never seen anything like it.

So knowing that I lost oil both times I drained all the oil from the compressor and flushed everything except compressor and the parallel flow condensor. The system with the sanden takes 200cc (6.75 oz) pag150, I estimated from everything I read 1oz in the condensor so I added 5.75 oz. I bought this kit https://www.rockauto.com/en/moreinfo.php?pk=12734309 it came with everything I needed even the fixed orfice tube. Pulled the system down for an hour then let sit overnight and still at 30" of vacuum so no leaks. Charged it to the 80% camaro system 28.5 oz refrigerant. Outside temp was 85°, gauges were still little low so I added a little more and ended up at 30 oz and got me in the ball park. I cut all air off to condesor and watched head pressure while reving from idle to 2000 - 2500 and never saw anything that would be concerning.

For the test drive the vent temp at 55 mph cycled at 37.9°- 41.2°, even looked down once on a back road and was at 36.3°. We drove the car all weekend with no issues and stayed nice and cool. Only difference was the orfice tube, not sure if something was wrong with the variable orfice but I cut it apart and couldn't find anything.

I've heard of similar stories with the variable orifice, and plenty of others with good reviews. Seems like it probably just depends on the luck of the draw, I guess.
I was really debating going with a VOT on my motorhome that I just had to R&R the AC system, but decided to stick to the fixed tube, albeit the larger size given the climate here. The replacement evaporator was also smaller, so I may have some optimizing to try to get the dash AC as cold as possible (dash AC will keep the unit cool on the road up to around 85* or so, after that you have to run the generator and the rooftop AC and take a 1/2-1 mpg hit).

Glad you got it sorted, sorry that meant pulling charge again...

A short update on the R12 system in the 86.
Recently, maybe 2 months ago, went over the entire system trying to get the most from what i had. Tweaking the charge via the Superheat method and was able to get low 40s while idling in the shop..
Over the past couple months where it's been cooking outside, 90s had some days when the A/C vent temp were good, others just acceptable. Last week when in the car by myself I wasn't happy, just knew something was amiss.

So got out the Mityvac and started looking for vac leaks in the controls of the system. My thinking is the system in MAX should be recirculating almost entirely interior cabin air, with a small amount of outside air. This is per the service manual. System would not hold a vacuum with the Mityvac.

My guess is on MAX the door for the outside/interior air is allowing mostly outside air and not recircing the inside cooler air. It is difficult for an A/C to get a very large drop across the evaporator. If outside air is 90 and dash vent temp looking for low 40s that's a 50 degree drop, can't happen . If you recirculate interior air at say 70 degrees that's a 30 degree drop to 40.

So after checking all the vac supply to the control in the dash and finding no leaks the controller, and radio is out of the car, on the bench. A bench test of the vac distribution switch and the switch is leaking, bleeding off vac and probably not holding the out/inside air door closed in MAX setting.

Remove that switch and found the nylon pin that hold the switch together and hold tension on the switch has almost failed. After trying to remove the pin one of it tabs broke off. I'm thinking I've found the culprit.
Looking for replacement switch or parts but have already gathered up parts to produce a new pin using an 8-32 screw and nut. Time right now to make a repair is not on my side, need this car to have cold air and driveable by the weekend.
One of our members here does rebuilds of these A/C controllers and I'm in contact with him already. Between the two of us I'm confident we can make that controller work properly again.
Bob

Doesn't happen often these days but, had a good day with the car today.

I knew down time on the car because of no A/C controller in the dash was not going to happen. I knew any avenue I went with the exception of a immediate repair of the vac distribution rotary switch would leave a hole there for weeks. So today repaired the switch.

Some searching, shopping and I know that vac distribution valve was sold as a 15-71389 A/C Delco replacement. You may find it on Ebay for ridiculous money, like $180.
No new controllers available anymore and used ones are 175 on fleabay. So need to repair what I got.

Sourced an 8-32x1 screw from my 50 years of collecting fasteners. An unlikely candidate, an Amerock screw for attaching cabinet hardware to wood doors and drawers. They are a flat head, a thin pan head, with slotted and Phillips, the perfect head as I found out later.
Reused the broken nylon pin, drilled it in the center to the 8-32 OD, .161". That took a progression of small drills, by hand, pin vise, so as not to damage the nylon pin, reusing it was the key to the repair.
Trimmed the legs shorter and had to relieve the inner side of the pins to allow the screw to not press again that area.
Next press an 8-32 nut in the center pocket on the backside of the white housing. The press fit of that nut into that pocket is near perfect, one of the reasons for using an 8-32. That pocket is where the tangs on that nylon pin "locked" to hold the switch together. When the tangs on that pin broke is when the switch stopped functioning, leaked vac.
Next is clean all the parts and check the faces of the rotary valve. GOOD. Cleaned the white nylon side and black "brains", program, sides of the valve with just some Westley's and a soft brush. It's the face of that "brains" that also can be a problem, it's a rubber channels of sorts and is rubbed, rotated, everytime you move selection. Mine appeared to have no defects. I've read be careful with old used valves, that rubber my be junk.

Back to the repair. Put a drop of pure silicone on the rotating faces of the two halves, 100% coverage, 99% wiped off. It's a vac switch the rest will disappear over time. The rubber on the black side likes silicone, the nylon don't care. Use a tiny drop of white lithium in the nylon pin to steel leaf spring contact area used to tension the valve. Assembled valve and adjusted rotating tension on the valve. This by rotating the valve as you adjust, tighten the screw. Doesn't take long to get the feel that to much is tooooo much. It's a pretty fine line.
Now mark the screw where to be cut, 1/2 thread out of the nut.

Next is reinstall the switch into the controller and start to slide the arm, rotate the switch. CRASH. The arm hit the side of the head of the screw, WHAT, it's already a thin pan head. Over to the vertical belt sander, thin down the head, and after a half dozen test fit it now a very, very, thin tapered pan head with but an x recessed in the center for a #00 Phillips. Didn't mike it but would guess .025" is all that's left, but BINGO, the arm passes the screw with just enough clearance now.

Remove the switch again, back off the new pin screw enough to put a drop of red locktite into the nut, tighten and reset the tension on the rotation.
Pin repair DONE!
Reinstall the switch back into the controller and verify if rotates easily without bind, ALLL the moving parts in that controller were gone over several months ago when it was removed for a new heat/cool cable and bellcrank for that heater/evap mechanical valve.

Wipe the controller clean and reinstall into the dash.
Ya gotta start the engine to refill the vac canister and charge the A/C controls. Kinda stupid to say that, it's more like you need to fill the system with nothin'.
The glove box door has the cable removed and can be opened and swung down, hang from the dash. The vac valve and outside/inside air valve is right there and easy to watch it operate. Wow it now doing exactly what it's supposed to do depending on the controller settings. ONLY in MAX A/C is the door 95% closed and allowing inside cabin air to enter the evaporator. BINGO, BINGO, BINGO every time the selector is moved, instant response.
Next is shut off the engine, the vacuum source for the A/C controls. Wait 20 secs and move the selection from MAX to NORMAL several times. The response is the air door responds until the stored vac in the canister is used up. BINGO, another test passed, the system has no vac leaks, it held vac until i used up the stored stuff.

Next run up the road with the Fluke digital temp gauge stuck in the center dash vent. It was 86 in the shop when I drove out into the sun. Up the highway in MAX cold, windows up, blower on med. Once the cabin interior started to cool down was then mid to high 40 as a low, cycling to low 50s. Just the finger test at the vents said MUCH BETTER.

Back in the shop where it's 85 in the shade seeing low 40s, 42-43, idling, just like it was several months ago. Shut the engine off and let the car sit for more than 15 minute. Then move the controller selector to different setting and listened to the various vac valves move until the stored vac was depleted. BINGO!
Over the next couple weeks will be able to insure all is well.

The lesson here is that outside/inside air door is critical to getting MAX cooling form the evap. You can't dump 100 degree outside temp on it an expect it to be happy.
A simple test of the vac system on our A/C is the how long will the canister hold a vacuum after the engine is shut off. After shut off you should still hear the various valve closing valves, the defrost, bi level and outside/inside as you move the controller between modes, until you use up stored vac.

As usual, kinda lengthy but hope this repair helps others. As I mention one of our member here can test and i believe repair these controllers,Tom Demarco. We haven't talked on the phone about my problem, we have swapped emails, but that will happen this weekend. Tom's a good guy, we've spent time on the phone before.

Something note worthy. The pin that broke on my vac switch appears to be the same pin used two more times in our controller, the electrical switch used for compressor function and the other small vac switch used to control the heater water flow valve. If, when, I every see another G-body, or mid to late 80s GM vehicles will own a spare for parts A lot of the controller parts are interchangeable between G, B, F and trucks. That particular 9 port 15-71389 vac dist switch may be specific to G, but the nylon pins are probably used in many other vac switches. Like so many parts for our cars they have evaporated, dried up. At the mercy of used stuff sold by bandits.

Brent, sorry about the hijack.
Bob

No worries at all Bob, glad you were able to get your situation fixed without much downtime or cost.

Thanks Brent.
Called Tom Demarco this afternoon and Brent knows that can get winded. Tom and I talked a year ago or so about his 402 BBC Monte and a torque converter problem he was having. Today was mostly about fixin the A/C controller. He's a retired ASA college Prof, car junkie, who could have fixed my controller, and tested it on his system tester setup. He's done many repairs/testing on these controllers. Anyone having problems with these vacuum 80s GM A/C controllers should talk to him first.

Tomorrow should find the time for some cruising, A/C system testing, weatherman says 80 degrees. Will do as before. Pressures, Superheat and vent temps, engine rpm, cycling, hood up, in the shop before venturing out on the highway.

Diagnosing the performance of the heater coolant valve will also be done on a cold engine startup and through the day. Hoping to see a acceptable temp on both the inlet and outlet of the heater core. The pipes are flat black and a pyro gauge should give a good result. I would expect them to be a close to equal in temp and maybe 100-110 degrees. Underhood temps where the heater hoses run into the suitcase are probably that temp on a hot day.
The heater coolant valve is not black plastic, probably zinc'ed steel , my second GM unit in the life of the car. If some hot coolant does pass through the valve when it's supposed to be near zero flow, the heater core will get engine temp hot. Just need to test that and see if that is another way to improve the ice cube production coming out of the dash.
When the system is working great you could use the glove box as a fridge. the primary reason this system is still an R12 system.

Then do the road test part with the temp gauge in the middle dash vent. The proof is in the pudding as they say. 20 miles on a Sun afternoon here can be anything these days, no idiots on the road or way to many. Will do a trip across town which could be a lot of stop and go traffic, usually a good workout for an all black car. My wife's all black 02 SS with black leather flunked that test with 4 people in the car when new and henceforth. A black exterior on any vehicle requires more production from the A/C system. Enough said.

Hoping that the 86's A/C is now a no brainer again. Just turn it on and be cool.
Bob

Sun late morning did a lot of testing, running the engine from cold until full warmed up, hot idled for at least 1/2 hour. Monitored the inlet and outlet temps of the heater core with the valve closed through the entire time, an hour or more in the shop. Also monitoring the rad inlet and outlet temps to check on the electric fan perf and how it will be effected by the rest of the sA/C stuff going on. Both Brent and I use the same electric fan controller which has it's temp sensor in the lower rad hose. My results have been excellent with that setup. 175 at the inlet to the rad and 130 coming out the lower rad hose, both fan running on high and the A/C requesting high fans also. The inlet coolant temp into the rad on this cooling system is so consistent, will only go up a few degrees even when run at WOT and abused. The other day it was over 100, A/C was ON and coolant temp doesn't move much at all.

As i was hoping the heater coolant flow valve is still function as expect, no hot coolant going into the core. Using the pyro gauge on the flat black inlet and outlet pipes cold startup they were give of take 85 degrees, room temp. Even after an hour of running, engine idling and 2000 rpm runs to check/test the A/C neither the inlet or outlet got above 115. Shooting the black A/C suitcase and other black things in the heater core pipe area and they were 110-115. So heater core valve bleeding hot water into the heater core and causing the core temp to be higher that it should be, not a factor at this time. Heater valve is still working well. A shame, only the plastic valves sold now, no more steel ones. #14032034 A/C Delco 15-5239
https://btsautoparts.com/products/15-5239-ac-delco-heater-valve-assembly-new

Also monitored the A/C dash vent temp, low side pressure, evap outlet temp, cycling pressure and got a go indication of where the Superheat is with all measuring while in the shade of the shop and at 82 degrees, hood open the entire time. So many things will influence the system performance you need to be aware of all the variable. Doing the Superheat method on a car is a guess at what you should be seeing at various conditions the system will need to operate within. So many thing influence how the system performs, Superheat checking for me is more about preventing the compressor from slugging liquid, looking for the low number you want to avoid. Less than 10 is no good, shoot for 12-13 as the low.
Doing a residential, commercial building A/C system would, should, be much easier to do as not any real greatly variables to deal with, a car is nothing but variables.

In the shop compressor cycling 25-46 on the low pressure, 82 shop temp, engine just idling on the fast idle solenoid to keep idle speed 800, both SPAL fans running on high (both the A/C requests high when the system high pressure is higher and the engine coolant temp/fan controller wants high speed on the fans to cool the engine), hood is up, A/C MAX and medium fan speed, full cold on the bottom slide control. Result was 44-50 degrees out of the center dash vent in the shop,

Drove the car home, digital temp gauge in the center port until after dark and back at the shop. A local farm store/restraunt hosted in season car shows once a month for years. Well as with so many of the places the wife and I frequented they are, have, disappeared. The Oley Turnpike Dairy is closing by the end of the month, have been there for diner or ice cream and many car show they had monthly for many years.
Before I left the shop in the 86 the rear triple adj shocks were set back to 0-0-0, at home got the wife and myself into a cold car and drove to Oley, maybe 15 miles for our last diner there. Dining room wasn't crowded but a 100 people, mostly little, young kids, standing in line for an ice cream.
A trip back to the house to drop my wife and back to the shop and can say she never complained being hot or uncomfortable hot in the car. She just hates the way it rides, but that has been that way forever.

The dash vent temps even with two sitting up front, MAX and medium fan speed were cycling 42-43 to 49-50 give or take. As I mentioned a lot of variable effect that dash temp. And unfortunately that is the true measure of the A/C performance, how many BTU does it take to get frost on the dash vents. And when you see frost, as in that black plastic vent is now white, you probably went to far. Not recently but another time when an R&R was done to this system occasionally would see frost.
Next Sat a good turnpike test of the system, an hour drive with the cruise set at 72, once in the morning, once late afternoon on the trip home. Expected again to be low 80s during the day. Monitoring the high and low vent temp when in the three different A/C modes, will be done.

Yep. always get carried away on silly things, like trying to maximize the A/C performance. I know they say a little knowledge can be dangerous, but have always wanted to know the why of things.
The valve in the controller repaired cost me a drop of red locktite and several hours of my time. But now not having it leak has not only fixed my erratic A/C vent temps and may have also fixed an A/F meter that I would see sometimes go stupid lean. My cruise A/F ratio is set at 15.0, sometimes it would be reading 16.0 even a tad leaner. That been going on for a while and was intermittent, just show it's ugly head occasionally. Put maybe 60 miles on the car since fixing that A/C control vacuum dist switch. Have been paying attention to the A/F gauge and, huh, can't say I've seen a stupid, steady lean gauge. Will be paying much more attention to the gauge but, huh. When the vac switch doesn't hold vac it would leak around it's perimeter. Just hard to imagine the vac hard plastic tubing that supplies the vac is but an 1/8" ID, it's getting it's vac at the rear of the manifold, could influence A/F that much.

So once again maybe able now to put this A/C system to bed and also figured out why i thought I needed to swap my other 800 cfm carb onto this engine. I could be that carb isn't the problem, it's the A/C controller that makes your engine lean, huh.

Lots of miles on the car the coming weeks. Next weekend 175 miles and 16 autox runs.
The following weekend have my room booked for UMI KOTM, that's a near 600 mile weekend. Not absolutely positive I will be there for that. The hotel room rate is ridiculous, more than double last year rate. But i know the car will be cold for that trip if it happens.
Bob