sjgrimsley

I don't usually post very much here, most of my time on this board is spent lurking in the background getting information and seldom giving back by helping out. So, I decided a short write-up of my A/C system would be a good way to give back to the TGO community.

I know a lot of us drive these car every day, some in hot, humid climates where A/C is a must. Living in north west Louisiana is always hot and humid in the summer time so I did all I could to make an R12 to R134a conversion actually work. I've seen on this very board where some have said 50* vent temps were plenty cold enough. Hogwash. 50* vent temps aren't even comfortable a 80* outside if there is any humidity at all.

Anyway, we all have been over the basics of a conversion. Evac, vacuum, charge. O-rings and new compressor will help it last past one summer, but it still won't get very cold. One trick is to use the ford blue orifice tube or even a variable orifice valve. They help while cruising but don't seem to help while idling in traffic.

Newer cars are designed to work well with 134a. The biggest improvement is the parallel flow condenser and electric fans that move massive amounts of air through it. Most have variable displacement compressors as well.

I already had the variable orifice valve. First thing I tried differently was the variable displacement compressor. Vent temps were better while cruising. Everything else still sucked. Upper 40's cruising and 55-60 idling.

Okay,so I used the condenser from a '97 Firebird, brand new, along with brand new dual fans for the '98+ cars. That helped quite a bit especially while moving in town. Initial pull down while moving was much better too. Still idling was hardly better at all. Mid 40's cruising but still 55-60 idling.

Hmm. Most vehicles have a shut off valve for the water heater. I installed one. No difference except after the car had sat off for an hour after being hot. The heater core didn't heat soak the dash so it pulled down a little quicker. While cruising, at most a 1* difference.

I decided I should keep the sun off me better by having my entire windshield tinted. Illegal? No. Llumar Air Blue 80. 80% VLT and blocks heat as well as, or better than 5% limo tint. This made a huge difference in comfort while driving in the sun. No effect on vent temps.



Our cars' recirculation door remains slightly open by design. Why? I have no idea. Newer cars seal the door off completely. So I looked into this a couple weeks ago when I had to replace the blower motor.







You can clearly see the door and the plastic limiter. The door opens up and stops at the limiter and mixes in some hot humid outside air with the inside air. I have no earthly idea why they did this. By the looks of it, its about 80% inside air and 20% outside air when in the MAX position.

I figured I'd get this cleaned up a little bit and seal it off with Duck Tape.
I didn't notice until I looked closer at this picture but I even missed a spot.



Here it's sealed off from outside air and you can see the size of the area where outside air comes thru when on recirculate.



You wouldn't think that would make a huge difference, right? Wrong! Initial pull down like a new 134a car, idles in town under 44* and cruises at about 38*. All on blower speed 2, where we all run it after cool down. Blower speed 3 just over 40*.

These were from today: 95*+ outside and about 60% humidity.

wgripp

iTrader: (1)

thank you!

sjgrimsley

Also I forgot to include that I had to have custom lines made up, and I even used the 4th gen discharge line muffler that's on the v6 cars. I can't tell it did anything.

My total system charge is 2.75 lbs. with 9 oz of PAG46 oil.

Fast355

iTrader: (2)

R134A still SUCKS, I was sitting idle today at lunch in my 2012 Nissan Titan, with the ambient reading 102*F and the blower speed cranked all the way up and with R152A in the system, the a/c was blowing 36-38*F at IDLE.

sjgrimsley

How does the r152a compare to the r290 in your other vehicles? I plan on swapping to something different later on.

I'd say what I got is just an example of things to do to make a 134a conversion actually work. Having said that, I can't imagine the performance of r290 with the changes I've made already. Lol

Fast355

iTrader: (2)

Put R152a in the 97 Express van yesterday after a defective fan clutch allowed pressure to build so high that it caused the relief valve to open and blow a large amount of my Duracool charge out. I replaced the Duracool with as much of 5 x 10oz cans of R152a I could get into the system. Based off the molecular weight of R134a vs R152a I came up with a charge amount of 44 oz for my 4.25 lbs system. 5 cans had the low side line sweating profusely, cold to the touch and the a/c temps with both blowers on high at idle at 49°F. While driving it dropped into the high 30s at 70 mph. Why 5 cans, you lose some when you side tap, more when you purge the hose, and yet more when you remove the can tap. Basically I just charge until the lines entering and leaving the evaporator become near the same temperature. When it stabilized out at idle, the high side was about 190 psi and the lowside about 37 with 95°F ambient temps. I kniw the electric pusher fan that I install with my trans cooler is going to help the idle numbers just need to get on that project.

885speed

iTrader: (1)

Subscribed.
Very good info.

Now you did all that from where the blower motor mounts on the firewall?
Also, what fabrication was needed to use the cross flow condenser? I imagine the lines at the least.

One more thing, do you have any links for the orifice tube and variable compressor? A/C is my weak spot

Ozz1967

iTrader: (4)

From everything I've read, GM built the flapper door thing to stay open to vent the cabin, bring in "fresh air", but all it does is make us mad.

Any links to the ring seals, orifice tube, variable compressor and info on the fabrication needed for the 4th gen condenser would be greatly appreciated! Thanks!

Spaceboy1980

iTrader: (6)

When I got my car, it had a 134a conversion already done to it. Blows very cold, I'm pleased with it.

formula1LE

iTrader: (3)

The vent door is a new one by me-nice upgrade! Anything to seal the outside off is good imo-less dust, dirt, fumes, etc. I also like to use foil-backed insulation on the entire outer firewall to seal out heatsoak fromthe engine-and, I also like to use high temp foam piping insulation underhood on the low pressure suction lines to keep them cooler, too. I have a 1995 Roadmaster Wagon as a daily driver and with stock R134A, it blows out very cold in any situation-it has the whole exterior firewall insulated from the outside and uses an aux. electric cooling fan molded inside the shroud where the mech. plastic fan resides. It comes down to insulation quality and high CFM fans to keep temps way down at idle. Stock 3rd fans just aren't designed well enough with respect to shrouding and thus, CFM capability. They may seem ok if you're used to it, but get in any newer car and you'd see a night/day difference.

That's why I prefer an over-the-top electric fan upgrade to help mask some of the inherent design "flaws" shall we say?

Fast355

iTrader: (2)

Well that was short lived, the high pressure relief valve is still leaking after opening and I cannot find the correct one for my aftermarket compressor ugh. Lost enough to stop cooling in less than 48 hours.

86gn

iTrader: (3)

Any chance you could repost your pics , working on my system now

sjgrimsley

First off, I'm embarrassed to have neglected my own thread for so long.

I may still have pictures somewhere on my laptop but I don't have it with me at the moment. It's quite simple though. When you remove the blower motor you will be looking at the recirculation door. You can pull it up by hand and see where it stops and see where to tape up and seal it. Obviously you won't be taping up the door anywhere since it still needs to open and close.

Also, if I were to do this over, I would use the aluminum tape that can be found in the HVAC section of Lowes or Home Depot. You can expect a very noticeable difference in vent temps after sealing up the space where GM left a gap to keep the door propped open.

lightsaber2003

I haven't seen the pictures you posted to go off of so I'm a little confused. I took out the blower motor on my 84' firebird to see where the flapper limits at but i didn't see any gaps. it looks like it seals up well if the vacuum pulls it all the way to the plastic limiter. the flap had a semicircle metal pieces on top that seals up and blocks off that gap that would be where you described. i don't know if that pieces is original or not though but it looks like its been there some time. I think my biggest problem at the moment is probably my transmission cooler being too close to the condenser the pressures seem high on the high side and the lowest I've currently got is 62 F at 2000 rpm on a 90 degree day. That was with only 16 oz of 134a so I think it needs more but I'm moving the cooler first.

Likethosecars

Your pics won't open for me. Can you repost them? Thanks!

sjgrimsley

You need to first make sure you have the correct charge. 16 oz slightly more than 1 can and not nearly enough of a system charge.

I haven't been driving the car since June 20, 2014. I found a good deal on a 2008 base Corvette coupe A6 and I've been daily driving that.

I will have to take new pictures of my system this weekend and host them somewhere else. Looks like photos are only hosted here for a certain period of time before they are removed for server space.

The flap will come up and seal completely on the bottom side of the stop, however there is about a 1" gap IIRC above that where fresh air is still allowed to enter.

Newer vehicles with computer controlled HVAC will open the recirc door for a few moments every so often, I guess to keep cabin air from becoming stagnant. Older cars can't do that on their own, so that's my guess as to why it is propped open and not allowed to fully close.

JT

iTrader: (1)

No, that is the problem. You hosted the pictures on Facebook and now they're not publicly available.

We do not delete attachments from our server - unless a member deletes their own content.

sjgrimsley

You know, I got to thinking about that after I posted and thought I may have posted them somewhere else already, and you are correct. I did post them on Facebook and they ended up being set to private. I just went back and changed those photos to public but they still aren't showing up. I will go back and edit the original post including them as attachments, as well as re-link them to the Facebook account.

I stand corrected! While sitting in my office at work.

siuol

Just a little comment. I replaced components in my 87 formula's AC system and charged it with RED TEK® 12a, works fine with nice cold air under any outside temp.

Louis

sjgrimsley

Original post corrected

sjgrimsley

I just quickly looked up this stuff on google as I have no experience with it. I see many good reviews. Glad it worked out for you. I would recommend sealing the recirculating door as well. Your initial pull down should be even better afterwards.

lightsaber2003

I added a some more refrigerant after moving the transmission cooler, that brought the pressures down a lot. still the best temp I got stationary was 48-49 degrees. it was actually mid 50's on the highway but I think that might be because the compressor was kicking on and off. It was only 78 outside. temperatures were a little lower in town. I thought I'd take another look at the re-circulation door.


it didn't have as large a gap as in your photo's since it had a rubber seal on the end but still some gaps at the side.



I've probably got about 19-20 oz of charge in there now which I think should be about right since its not the stock setup. It's probably closer to the 4th gen charge amount since the hoses aren't as long. I'll wait for the temperatures out to warm up a little mid week and try it out again. I also moved the pressure switch out about 1/2 a turn counter clockwise I'll see if that helps.

sjgrimsley

That's interesting that yours has a seal on it.

Also still sounds like not enough 134a. My V7 compressor is in the same location as yours, and I am using a fourth gen condenser with the original evaporator core, and to get the correct pressures and performance using a RobinAir recovery and recharge machine required 2.75 lbs. or 44 oz. I took many attempts to figure out the correct charge for my custom system just because of the fact that I was using a variable displacement compressor which never cycles. The a/c system exibits the same symptoms for undercharge and overcharge. I started out at the fourth gen system charge of (I think) 1.5 lbs. and got nothing but hot air, testing on a 95F+ day.

badgta

iTrader: (4)

R-290 = PROPANE!!!!!

If you still have old R-12 stuff, have it recovered and charged with MO99 or Hot Shot 2.

FireDemonSiC

After rebuilding my entire AC system and charging it with 134a, I recorded a maximum temperature delta of 50F at the duct, going down the highway on a high 80s day with decent humidity (Enough to condense on the outside of the windshield from the AC).

rsrmoore

Subscribed

sjgrimsley

The alternative refrigerants aren't being discouraged here. In fact, their performance will also be improved by sealing the recirc door on cars where it is left hanging open like mine. If you want to use all the factory 3rd gen a/c equipment with an alternative refrigerant, I would still recommend doing this little modification. Initial pull-down will improve getting you cooler quicker. If you leave it on recirc, your compressor on-time will be reduced as well.

carattini

I don't claim know anything but if you seal everything doesn't the Monoxide exhale from the people inside the car increase and over time be halmfull?

sjgrimsley

I don't think any of these vehicles can be sealed that well IMHO.

lightsaber2003

So i think I've got it dialed in as good as is possible. I'm not really sure what the oz is since some got let out and added back in but i'm going to guess about 26 oz total. but that's a real guess as i kind of lost track of the totals but probably about 2 full cans and just a touch more. I did some of the dialing in on a truly awful day 90 F and 80% humidity. the best i got the vent down to was 62 degrees before i added a little much and it went up to 64. at 1500 rpm i was reading 39 psi on the low side and 325psi high side. the low side and vent temp seemed about right for this chart.


however the high side is much higher. That's always been the case however. I assume that its because of the smaller orifice tube and the inefficient s coil condenser.

Testing it today its 86F and about 50% humidity. I was getting about 52-53 out of the vent sitting at 1500 rpm with about 30 psi low side and 250 psi high side. those pressures could be off though I lack a little confidence in my cheap gauges. Driving it down the road it got down to about 50-51 vent temps with it on max and with the interior being 80. I think it would have went down farther if it got a chance to cool down the inside. it seemed to steadily go down very slowly. I drove it for maybe 30-40 min. It wasn't like last time it did get cooler at high way speeds and warmed up a little but not much at slower speeds.

I don't think that the low side pressure switch adjustment is actually working. It seems like its been stuck at 25psi for so long that the internals must be frozen there moving the screw doesn't seem to change it. But it seems to be working well enough I'm not going to mess with it. I think 30 degree's less than the interior temp is about the best you can do with r134a. but I'm sure the vent door being sealed helps achieve that.