oh yeah..it's kinda like horsepower improvements in our na cars..even small improvements still take big money..i'm only only willing to spend so much money to be just a little bit cooler. most of my plan involves 'fixing problems' rather than involve 'upgrading'. the fan is the only real upgrade i'm considering for now.
ryan

On my 87 I have installed from Rennaire; new barrier hoses, a Procooler and Evaporator. Stock front and rear condensers with a new sanden.
My son and I did the hose install with phone support from Ron. Great guy ! A vaccum and 32oz of r134 and no leaks the first time. But..still only getting 55 degree temps from the center vent middday ambent temps around 95-98.
Still not cool enough at all for fla daytime temps. I need 30-40....My next step is a fan in the rear decklid to help with stop and go traffic, .... a Kuehl Vent, Kuehl fender condenser and Kuehl rear deck condenser.
Also replacing the r134 with this hydrocarbon boom gas I just read about. :)

seeeu,
yeah, what you've described is what's so frustrating. you've arguably done quite a bit and it's still decent at best compared to almost any more contemporary front-engined water-cooled car's a/c. the basic design of the system in our car leaves absolutely no room for less than perfect working condition components..and lots of 'em. you have to become an amateur hvac guy to achieve anything even marginally good in our cars! :(
ryan

All with A/C problems may want to consider this:
I just pulled out the footboard from the passenger well, and checked out my evaporator coil. It was dirty, which is to be expected, since it sucks up all of the crap off your shoes. I squirted up there with some Simple Green (I usually would use evaporator cleaner, but I'm out), Let it sit for awhile, and took the garden hose and washed it out real well (yes, I am crazy). Blew it all out with the air compressor.

I folded the overhanging bit of carpet so that it doesn't block up the return air. My air was already good, but I did get some improvement which I will quantify at work tomorrow with my super duper infrared thermometer.

Make sure your condenser coils are clean also. If your heat transfer surfaces are dirty or blocked up, all of the upgrades become an exercise in futility

If all else fails, install one of these:

http://forums.pelicanparts.com/uploa...1122250901.jpg

Pat

Seeeu911,

I think you have too much refrigerant in your system. Have you tried sucking out about 4-6 oz.?

Cleaning out the condensor may be a good idea as well and changing the R/D. I was also curious about my pressures. I "think" I was getting about 25 on the low side and 250 on the high side...does this sound about right. Also, my guages have three inner circles of #'s which are listed R12, 22 and one other which I forget, and it appears to list temperatures. I assume I use the outer pressure lbs/markers but what are the inner #'s for?
Also, does anyone have a suggestion for a drop in R/D replacement or should I go OEM if I want to avoid having to fabricate something?
Thanks

pat,
that thing looks kinda big..i might wanna tow it behind me instead? ;)
ryan

Hey buck check out the ProCooler... I've heard good things about it, and I'm considering purchasing one to replace the 20 year old OEM unit in my car... look at the performance specs on it! SmileWavy

www.procooler.com

Pat, The return air system on 911's has baffled me for years. It seems that it is very easy to block the flow of air on the passenger side with floor mats and carpet. The driver's side is the biggest mystery. I love that 3" duct from the evaporator the dies in the pedal board. Toss some carpet and floor mats on that side and its all but useless. The weirdist part of the design is that the air is just recirculating under the dash because there is no nice clean way of pulling hot air from the rear of the cockpit. What you have is a pressurized cabin that resists the flow of incoming cool air. I recall a trick used by HVAC guys to heat rooms that lacked a return air vent. They like to open the window a crack. Someday I going to figure out how to use the tunnel as a return air duct and at least pull air from under the seats rather then the floor board area. In the mean time you might want to crack the window.

Ron:
Well, the air has to go over the coil. The only way on mine for it to do that is to go onto the trapezoidal hole under the passenger floorboard. I had the A/C running yesterday, completely blocked the return, and air was still coming out of the vent feed tube. I have an aftermarket system from Performance Aire, which the PO had installed in 1999. Anyway, I have to do further investigation to see the source of the return air bypassing the coil. It may welll be the mysterious 3" duct you speak of. I will check on that tonight. I think the entire 911 ventilation system was designed during Oktoberfest.

I think the Performance Aire system is a bit different from the factory system. I need to pull the fan box out to really get a better idea of it, which is a winter project.

In the HVAC world, lack of return air flow will ice up a coil; it is symptomatically the same as a system low on gas. I think the guys out west don't see the same problems we see here, due to the high humidity levels and resulting latent load on the coils. The unit has to do a lot of work to dehumidify.

You are absolutely correct about the carpets and other junk being in the way...thats why I folded over the passenger carpet to the edge of the footboard, so that it didn't hang over the tunnel and block the air.

Maybe I'll get some photos, and you can advise if my system and the factory system are similar.

Thanks!
Pat

Serviced the A/C on an 84 Carrera this past Saturday. System was stock but had been converted to R-134a two years ago (ester oil in compressor) with no flushing of condensers or hose replacement. Was blowing hot and remaining refirigerant charge was down to 30 psi static (compressor not running). Replaced o-rings (4 total) at receiver/drier and at compressor, leak checked and pumped down for 2 hours and charged with about 26 oz of R-134a. Produced 55 F air at vents idling at 2000 rpm with back deck lid down (90F deck lid intake air and 30% RH ambient) and 38 F on the highway. Cheers, Jim

Hey Jim (or anyone else whose knowledgable)

Refilled my A/C, I've got front and rear condensors, an 18" static underbelly, a subcooler, per Jim Sims design, R134a and a sanden compressor, new R/D and hoses. At 90 degrees outside and 50% RH, I'm getting 50 and 200 psi at idle and 30 and 225 psi at 2000 rpm, and I can get 48 degrees while driving, should I leave as is, bleed out some 134a, or add some more?

Thanks for any thoughts, btw, last we spoke Jim you suggested bleeding out some. Do you still think the same?

I damaged the rear condenser last week while installing a fan in the carrera tail..managed to lock myself out of the engine bay too.
I went with the 30-32 r134 that Rennaire recomended, but the ac tech who was at my house had to leave before we could do anymore testing. I drove it for a week or so and it never got below 60 idling and 55 at highway speed...thus the fan attempt. I now have to repalce the condenser so I might as well go Griffiths the rest of the way...
Crachian, thats a good tip. I will plan to rechage starting with 26.

OK, I did some temperature measurements on the way home. 55 mile trip, some traffic for the first ten miles, with a five minute stop halfway. All of the following data was collected with an infrared temp sensor, with a probe in the discharge air vent.

About an hour before leaving work, I checked the system...58 degree air idling at 2000 RPM, with two big fans at the engine compartment. 94 degree ambient, 58% RH. It was hot in the car at start up. After sitting for a few minutes, high side head pressure was over 300 pounds, condenser temp was at 140 degrees. I was worried about blowing out the front compressor seals, which have always showed signs of slight leakage.

On the highway part of the ride, I had right around 48 deg discharge air, with 77 deg air at the passenger footboard, and 86 degree air just to the right of my right foot at the end of the tunnel, so the return air was about 80 degrees. The rocker panel on the right side was 94 degrees. The door panels were at 94 at the start, but finally cooled off to cabin temp. I jumped out quickly when I got home, and had 140 degree condenser temp (at the decklid condenser, I did not check the underbelly one), my new Mocal oil cooler was at 235 degrees (the new scoop did not arrive from our hosts yet, but I did put air deflectors in to pass the bulk of the air over the cooler), the left side valve cover was at 233 degrees, and the fan inlet temp was 140 degrees. The rear bumper was 140 degrees, the bumperettes were only 105. Incidentally, NY Thruway surface temp was 110 degrees.

Summarily, I was getting a 30 degree split across the evaporator, which is about what can be expected. The decklid condenser throws a large amount of heat into the engine compartment, witness by the very high oil and surface temps.

I generally just put the windows down and open the sunroof, but I figured I'd get some data for the greater benefit of the masses and myself. I'm guessing this added about 20 degrees to my oil temps, I will verify that later.

It was cold in the car, however, and after awhile, I had to turn the fan speed down and re-adjust the vents to keep it from blowing directly on me.

Hugh, Your high side system pressures seem okay but the low side is likely too high. I don't recall; what is the status of the expansion valve? Is it new or did you just check it for a clogged screen? You could remove some refrigerant and see if that helps; easy to replace if that isn't the problem. Jim

Jim, I don't have a pcar expansion valve. I pulled it apart and no screen was apparent. I could blow easily one direction but not the other on the valve, so I put it back in. BTW, it was wrapped in some tar-cloth, which I have to still replace. Why do they insulate the expansion valve on which is on the hot side of the system? Obviously to hold the heat in. Is this so that there is a greater temperature/pressure drop across the expansion valve, and thus more reject heat? Just wondering. I'll try bleeding 5 psi out and see what happens. Thanks again.

I believe the idea is to insulate the capilliary bulb which should be clipped on the cold side (see the evaporator photos in Thunder Punk's A/C thread); by the way what side is your system's capilliary bulb mounted on? Jim

Its clipped to the cold side. I'll try insulating the expansion valve tomorrow before I start playing around with the pressures. When you say what side is my system's capillary bulb mounted on, I assume you mean the end of the long tube on the expansion valve, which as I said is on the cold side. Jim, thanks again.

Hugh,

The sensing bulb, or pigtail, attached to the end of the capillary tube atop the expansion valve, is typically placed (as noted) on the evaporator outlet pipe: traditionally its placed on the top of the circumference. The higher position or location on the outlet pipe, in theory, is so it is picking up the coldest section of the pipe as a/c oil typically lays in the bottom section which can insulate outlet vapor temperature from reaching the bulb:

As the outlet refrigerant vapor temperature rises it causes the gas in the capillary tube to expand which opens the expansion valve, and as the outlet refrigerant vapor temperatures decreases it closes the expansion valve; hence the valve is usually throttling within a range of the temperature.

Insulating the pigtail with the common black insulation cork tape allows the pigtail to focus on the evaporator outlet vapor temperature rather than ambient temperature surrounding the unit.

A follow up of my earlier post on this thread. I just installed the HC-12a drop in refrig substitute in my 85 R-12 system. It was 95 degrees today and the A/C was nice and cold. I decided against the ES-12a brand for a personal reason. It took a total of 18oz of HC-12a which is equivalent to about a full system charge of R12. I was almost totally empty of R-12.It has oil in it as well and no mods required at all. It was easy and total cost with the filler hose delivered to my door was $49.
This is where I got it. http://www.foxtoolsupply.com./ Mr. Fox is super nice and helpful and explained it all to me and only took 2 days to get.