?'s for the a/c guru's
 

when doing an a/c refresher at what point do U install a new receiver/drier? before or after evac?
one of my cars has been converted to 134a and i don't think the p/o's a/c mech replaced the r/drier...with the rising cost of 134a here in Cal would it make more sense efficiency wise to go back to r12 while i'm doing a new r/drier. tia.

Before you vac as you have to open the system to install the drier.

You want to install the drier just before you vac. Otherwise it will suck moisture out the air and not function properly. According to Jim Sims of the board, r134 is about 11% less efficient than R12. 134 seems to work well if you have enough condensors, but I shouldn't speak, I'm still trying to get my conversion to cool as well as some others that I know of.

thanks guys!! for some reason i was thinking that evac the system with a new r/d would contaminate it.

Turn6: If your system's apart, consider adding a ProCooler in place of the R/D.

Jim Sims: You're in LA and you haven't scheduled a local a/c seminar? What's up with that? :D Enjoy our fair city. Let us know if we can help you enjoy SoCal!!

A/C info. mods. needed
 

Jim Sims:
You indicated on another thread that you installed an extra fan on the evaporator inlet (under the passenger board) at the foot well of your '73.5 911.

What diameter "pusher-type" fan works best?? Where can I purchase one also??

Thanks,
Hz:rolleyes:

If the system is free of R12, you would have to remove the old r/d and drain the old lubricant oil out before installing the new r/d. Then you would evacuate with a vac pump for 2-3 hours to get all the moisture and air out, then recharge with new freon and compatible oil.

We have used MP-39 as a drop in for 12 in autos. Works quite well.
Pat

oops!

http://www.dupont.com/suva/na/usa/products/mp39.html

Pat: Is MP39 approved for vehicle use?

We have so much equipment at the facility I manage, that my crack mechanics tried this a few years ago on cars. The autos we have tried this on have been leak free, and have not had any problems to date. DuPont evidently developed this for refrigeration systems, such as kitchen and beverage coolers. Approval for mobile units is not implied by DuPont, but it is not disapproved either. May be a political thing. Likely because cars are the biggest leakers into the ozone layer on the planet, and MP-39 contains (I think R-22, it's in the link) in the blend, which is slated for phase out. R-134a is a long term solution, but the retrofit price tag is high.

It doesn't contain any of the hazardous stuff, such as isobutane or propane. We tried it, it works OK. It's available, and cheaper than R-12. I used it last year, didn't really notice a difference, but refilled this year with 12, since I had a bottle in the garage, and needed the car for the LI meet the next morning (I had to disconnect the A/C over the winter to get my steering rack out).

My crack staff and I are still working on a solution to get colder evap temps in the SC, as the condensing temps are ridiculuously high. If we gat any btter results, you guys will be the first to know.

Pat

hifeverz

2 inch 12vdc computer fans, make sure you hook them in parallel, not series.

hifeverz


For info on my evaporator booster fan and installation see:

http://forums.pelicanparts.com/porsche-911-technical-forum/117046-liquid-r-134a-going-forward.html?highlight=forward.

The larger fan one can install the better but be aware of the current draw and the fact that the larger fans tend to be noisier. The one I installed only draws .45 amp and still fits behind the passenger side floorboard.

Jim

"My crack staff and I are still working on a solution to get colder evap temps in the SC, as the condensing temps are ridiculuously high. If we gat any btter results, you guys will be the first to know."

Better condenser performance (improved air flow, more passes, size, density of fins, etc), the addition of a subcooler and the elimination of unwanted heat gains are the solutions. It ain't magic, just thermodynamics/heat transfer.

I can make literally make ice (31F vent temperature on the highway) with R-134a using just the engine decklid condenser and a subcooler.

Cheers, Jim

jim,
i seem to recall seeing a pic of your subcooler being mounted near the rack and pinion area..what do you think of just this addition alone? i have a sanden, stock single decklid condenser, r/d, etc.? running freeze-12 too which is epa-approved..what say you about that stuff? any experience with it? if you could do only one mod, the more efficient condenser you purchased or the subcooler, which would you do?
ryan

jim,
the shop i went with (here in the sticks) uses freeze-12 and r-134..the freeze-12 supposedly can be used in a r-12 system, so its why i went with it. this fall i plan to replace all hoses with new barrier, new r/d and am considering your subcooler. all other things being equal, would you guess this mod to be worth maybe 10 degrees? my present system is decent as long as temps stay below 90 degrees..beyond that, it's a controlled sweat..i can't check vent temps accurately with a simple thermometer, but in 100 degree heat, my car sat in the sun with the windows cracked and the cabin went to 105..after starting the car and driving home for an hour with a/c on max (does that knob really vary anything??) and fan on hi the cabin temps never went below 90 degrees..nice, huh.. :(
ryan

Jim:
Is your evap performance based on conditions at Los Alamos? I would imagine design conditions are a bit less than here in NJ, where we had 95DB, 74WB, and I have a huge latent load on the evap.

I had four semesters of magic, er, thermo/ heat transfer, but they still didn't want me at Sandia.
http://www.pelicanparts.com/support/smileys/wat5.gif

Pat

Jim: I already have one subcooler in my system (a ProCooler).

A. Is there any downside to adding another?

B. Can I even install another one?

Comments/thoughts appreciated.

Scott

scott,
jim should probably weigh in on this instead of me, but his is installed near the front skid plate..there's a thread of his on here somewhere showing pics. didn;t know where he got the term 'subcooler'..is that then what the proccoler is considered to be and not simply 'more modern' a r/d replacement?
ryan

BigChill: The ProCooler is a subcooler. It actually uses the system's R12 to cool itself, if I understand correctly.

Jim is an expert on this stuff. I'm sure he can explain it better than me!

Scott

scott,
thanks. do you know of anyone who simply performed a single, direct replacement of their old r/d unit with a procooler and documented what the effect of this single upgrade was? i know i've read about upgrades including a procooler when other things were done as well..you know what i'm asking.. ;)
ryan

That's always been the unanswered question. I did a lot of other upgrades, so the PC was just one piece of a bigger picture. I'm happy with the results, but can't document how much of a role the PC played in the improvement.

Scott

BTW, Jim, that is a nice install you did on the return fan setup for the evap.
What is this precooler, or subcooler, being mentioned above. Is this just another condenser?

Pat: It's a subcooler. It replaces the receiver/drier.

Scott

This thread has pics of Jim Sims subcooler. I made one following his directions and the hardest part was figuring out where to stick it. I put it just outside the back of the skid plate. You have to measure carefully when making the hoses. Here's the link http://forums.pelicanparts.com/showthread.php?threadid=162544&perpage=20&highligh t=subcooler&pagenumber=2

yeah, that's the thread i was referring to..thanks, hugh. btw, what are your own impressions of the job it's doing? i seem to recall you making several component upgrades at the same time though, right?
ryan

Right now...my SC is down at Rennaire getting the new Evaporator and Barrier Hoses like Mark Wilson.

When completed, I will have just the stock rear condenser, Pro-Cooler, upgraded evaporator, new barrier hoses with a sanden compressor.

I will post the final results in the TEXAS heat, >95 degrees in full sunlight on a hot road in Dallas traffic. That should be a good indication of the cooling power of this affordable combination. :)

kemo,
that will be interesting data..new hoses shouldn't affect vent temps, but we do know it will save refrigerant charges for sure..can't say what a new evap will do (anything about the new evap an upgrade over the original?). i have the same sanden and stock rear condenser as well..i'm anxious to hear your results. did you take baseline vent temps by any chance before leaving the car at rennaire?
ryan

Bigchillcar

I'm not where I want to be. My car is an ROW without factory air, and has very different ventilation plumbing behind the dash than a US car with factory air. So first off, I'm not getting the blow that I want out of the vents.

Second, I'm probably going to take out the fan-powered condensor next to the catalytic converter. When stopped, that condensor see over 120 degree air and it can't be cooling, in fact, I think its adding heat to the R134a in the system. I may or may not put that condensor in the front left wheel well, I have to see how much room I have in there with the washer bottle romoved, the condensor is 12" by 12" by about 3" thick with the fan.

Three, I tried using a couple of computer fans in lieu of the real Behr front condensor fan. I may spring for the $250 new one if I can't find a good used one. When I'm driving at speed I get around 40 degrees at the vents, when its 85 outside. The problem I have is in traffic when vent temps go up to 60 degrees.

How well does the subcooler work? I don't know since I don't have a "before" and "after" Jim Sims says it only works if you have excess condensor capacity, I'm not sure what constitutes "excess" perhaps more than just the original two condensors. Jim Sims recommends that I get a REAL vacuum pump and not one of the venturi air compressor types and run it for several hours with the car out in the sun. I may try that as well. $250 for a front condensor fan, $210 for a vacuum pump, about $100 for 134a gauges versus paying someone to do the pump and recharge, hmmmm.... the wifey is (not) going to be pleased.

hugh,
trying to recall..are you the one with the thread about putting a condenser in the driver's side rear wheelwell? you tried computer fans but now considering the fan typically used in front wheelwell condensers as i understand it? do you have a fan for the rear deck condenser? i know if you have cis, you must have modded the airbox for fit. what's jim's story with vacuuming the system out? starting over fresh?

as for the wife..what she must understand is that this is not only an important upgrade for your car (can't have hubby having a heatstroke while driving), but this is important research for your fellow man and p-car connoisseur.. ;)
ryan

Ryan

I had some computer fans on the rear condensor when I had a non-stock really small condensor, but not since I bought a full sized condensor, I may put some back on, they helped in traffic. I do have computer fans on front condensor, but may buy a real squirrel cage unit ($250 new), I have an 84, so no cis. Pulling a vacuum is to start fresh, but Jim thinks that the cheap ($20) venturi-type vacuum pumps that work off of a compressor don't pull enough vacuum and that you'll get better performance (colder temps) using a two stage vacuum pump.

I may put a condensor in the l/f wheel well, if the one that is currently next to the cat. have fits.

unfortunately I did not. Im sure someone out there will have a stock A/C system out there to compare to. If I can have 30-something temps comming from the vents in traffic during a Dallas heat wave, I will be very happy.

Subcooler doesn't replace a receiver/drier but can be combined with it (as in a Procooler). I estimate I am gaining 10 to 15 degrees temperature drop over system without subcooler. I just took my car on a 3100 mile trip and A/C worked well everywhere (down I5 from Davis to LA - there was plenty of humidity), in downtown Hollywood traffic and charging up Cajon pass out of San Bernardino, in Needles, CA in mid afternoon and across AZ and NM. Jim

jim,
b4 i renovate this fall by replacing hoses and r/d (maybe adding subcooler)..i guess you would still highly recommend vacuuming everything first b4 taking apart, then performing the upgrades? even replacing the r/d and hoses it would probably be benificial for the condenser, compressor and evap i'm guessing. i know where to mount the subcooler, but again, between what components inline do you put it?
ryan
ryan

If you have R12 have it pulled out and recovered at a shop. You pull vacuum just after you've connected everything together. Keep the new r/d sealed until just before you connect. Subcooler has two pipes with four openings. You connect the two big ends to the big hose between the evaporator and compressor, and the two small ones between the r/d and the expansion valve on the evaporator. you'll need a flaring tool that can accept a big enough piece of copper tubing 1/2" or 9/16" I don't remember, you get the flare fittings at Home Depot, Loews, etc. in the little speciality fittings drawers. You have to use flares on the subcooler, because you can't find o-ring copper male fittings to hard solder to the subcooler.

Just got loaned a real vacuum pump, gauges and a big jug of R134a, for free (actually a dozen donuts)!!

good buy for donuts.. ;) thanks for the info, hugh..i can see i'll need to do a little more studying and figuring where addition of a subcooler would be involved.
ryan

Rats, gotta buy a 134a fitting for the vacuum pump. Gotta find an A/C parts supply shop tomorrow.

shoulda bought chocolate instead of glazed, hugh! penny-wise and dollar foolish.. ;)
ryan

I'm going down this trail to upgrade the a/c in my '79 SC. The front condenser blower requires at least a new motor.

http://forums.pelicanparts.com/uploa...1120028910.jpg

I'm considering enlarging the penetrations in the front of my tub to accommodate a 9" fan. It's specs are 3.5 amp, and 1400 cfm
http://forums.pelicanparts.com/uploa...1120028689.jpg

Questions are:
a) would this be an improvement?
b) would such a modification "damage" my car? (Non-stock kludge!!!)

Thanks