?'s for the a/c guru's

[turn6]

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.

[Tim Hancock]

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

[Hugh R]

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.

[turn6]

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

[scottb]

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? Enjoy our fair city. Let us know if we can help you enjoy SoCal!!

[hifeverz]

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

[tshih]

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.

[patkeefe]

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

[patkeefe]

oops!

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

[scottb]

Pat: Is MP39 approved for vehicle use?

[patkeefe]

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

[Hugh R]

hifeverz

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

[Jim Sims]

hifeverz


For info on my evaporator booster fan and installation see:

Liquid R-134a going 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

[Jim Sims]

"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

[bigchillcar]

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

[bigchillcar]

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

[patkeefe]

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.


Pat

[scottb]

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

[bigchillcar]

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

[scottb]

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