DIY Air Conditioning for Old Porsches Part1

[69BahamaYellow]

As much as I appreciate the simple, no-nonsense design of the old carbureted 911’s, driving them on hot summer days in Texas, without air conditioning is unbearable, so after having done a complete restoration of my 1969 911T, I wanted to build an AC system from as many original parts as I could find, but upgrade the compressor to a modern rotary design. After many months of searching for parts and fabricating new ones, I finally have a working system (just in time for summer). The Pelican Parts Technical Forum proved to be a valuable source of information, so the following post will hopefully give others some ideas and tips that I learned from my own project.

To begin with, a friend supplied me the under dash air vent, evaporator box with fan, front and rear condensers, receiver/drier, and all the old hoses from a 1971 donor car. I should have taken a picture of the parts “as received”, but this is what they look like now in my car (I re-upholstered the under dash air vent, but I’m still looking for a missing knob…..)





The hoses and receiver/drier I got from my friend were rotten, but I salvaged the hose ends for re-use on the new system. If you plan to re-use the old style condenser and evaporator with flare style fittings, the barb and nut from each of the old fittings will be useful, and they can be recycled for brazing onto new lines pretty easy. If you can find a source for #12 #10, #8, and #6 braze on flare fittings, then don’t bother saving the old pieces. I never could find them, so it’s a good thing I saved my old fittings. The picture below also shows a clear vinyl tube and air drier (purchased from Harbor Freight Tools), and used for flushing the system before charging. This will be described later.



My car was typical of the older 911’s, in that it needed new rockers and a floor, so when replacing the rockers (during my original restoration), I thought I might want to someday add air conditioning to the car and decided to run metal line inside the (Inner) rocker panel for a cleaner look with better protection of the lines. Each line is about 7 ft long and fits nicely behind the heater air hose. I used 5/8” (#10) soft copper for the low pressure line and ½” (#8) soft copper for the high pressure line. I also wrapped both with rubberized foam insulation to dampen noise and prevent sweating of the LP line inside the rocker area, before I welded in my new rocker panels. The copper line is cheap and readily available from hardware stores, but now that I have the experience of installing it, a better choice would be to run aluminum tube in the same #10 and #8 sizes, as it is much easier to bend and fit into the tight confines of the 911’s rocker area, it is lighter, and is easer to braze on fittings with aluminum brazing rod than to braze on fittings to the copper line that I used. The aluminum tube is harder to find, but Aftermarket Air Conditioning For Automobiles and AC parts has it, and you will need it anyway to fabricate the lines to your compressor.

When you are running your AC lines, remember that as the refrigerant condenses from gas to liquid, its volume decreases, so you need progressively smaller tubing after the condensers to keep the pressure from dropping before the expansion valve. The OEM setups look something like this:

Compressor to rear condenser: #8 (1/2” diameter)
Rear condenser to front condenser: #8 (1/2” diameter)
Front condenser to receiver drier: #6 (3/8” diameter)
Receiver drier to evaporator: (1/4” diameter) – I had to use steel here
Evaporator to compressor #10 (5/8” diameter)

Oddly enough, I found that #10 fittings were smaller diameter than #10 tube (even though they fit perfectly. #12 fittings were the same diameter as #10, so I used these instead.

Mounting the condenser, evaporator box/fan, and under dash air vent are fairly easy, as these parts bolt right into the factory locations, but I did run into a few problems with the rear condenser. For starters, I did not want to modify or remove my OEM air cleaner, and the condenser, even though it’s only 1 inch thick, would not fit between the air cleaner and the deck lid, but it was close enough, that I could shave off about 1/8” worth of fins around the edges of the condenser to make it fit, slightly recessed, into the area of the deck lid grille. The picture below shows the finished installation, but I should have taken a picture of the modification process. To make the modification, I applied masking tape to the outer edges of the rear condenser and ran it over a table saw fitted with a masonry (grinding) blade to remove the excess. The masking tape keeps the fins from bending over as the blade passes by; a little finishing with a Dremel tool makes a very professional and OEM looking modification. The bottom picture of the 3 below is the best illustration I can give of the cut fins on the condenser.





Routing The AC lines was a challenge because I wanted to keep the total length to a minimum, to reduce refrigerant requirements and eliminate any sharp bends for efficiency. This required making custom lines for everything. I also wanted to use 134a refrigerant, so I could charge the system myself. This required a different receiver/drier than what I could buy from Porsche, but turning to the internet, I found Ray’s auto air conditioning Ray's Auto Air & Heat - Auto Air Conditioning Parts & Accessories, A/C Hoses & Fittings, and they had all the special flare fittings, hose clamps and grommets, receiver/drier, and even the exact 3 speed fan switch and evap temp controlled compressor thermostat switch to replace the originals from my under dash air vent. Here is a parts list from Ray’s

Qty Part # Description
1 1295 #12 Weld-on Stem, Steel
1 1463 #12 Compression Fitting, 5/8” Tube
1 3199 #12 Weld-on Stem, 5/8” Tube
1 3002 AC Fitting
1 3000 #8 Weld-on Stem, Steel
1 112062/1301 #6 Female Flare Fitting, 90deg
48” ACH12 Standard #12 Barrier Refrigerant Hose
3 08020004 1 ¼” #12 Loop Strap
1 235-1459 #10 Compression Fitting
3 08020003 1” #10 Loop Strap
1 06900705 Weld-on Charge Port, Steel, 134a Low (Optional front charge port)
2 242-1404 13mm Low Side Charge Cap
1 06900204 Aluminum Weld-On Charge Port, 134a Low
3 00212082 #8 Female Flare, 90deg
1 00112062 #6 Female Flare, 90deg
1 235-2993 Weld-on Stem
1 207-101 Receiver/Drier, #6 Flare (4 Seas.–33318, Everco-A5873)
1 211-106 Universal Rotary Blower Switch
1 211-102 Thermostat, Rotary, 36” sensor lead
4 06300490 Aluminum Welding Rod
1 06900205 Aluminum Weld-On Charge Port, 134a High
3 242-1390 Valve Core / Standard Schrader
1 06900020 Weld-on Switch Port, Aluminum
1 242-1403 16mm High Side Charge Cap
1 00227710-A AC Fitting / 2099
1 211-290 Binary Pressure Switch
6 08020002 7/8” #8 Loop Strap
1 00212080 #8 Female Flare, Straight
1 00222710 #8 Compression Fitting, ½” Tube
1 00220082 #8 Male Flare Bulkhead Fitting, 90deg
1 00212062 #8 Female Flare Step Down 90deg
2 235-1816 #6 Weld-on Stem, Steel
4 08020001 3/4” #6 Loop Strap
120” ACH08 Standard #8 Barrier Refrigerant Hose
1 00120060 #6 Male Flare Bulkhead Fitting, Straight
84” ACH06 Standard #6 Barrier Refrigerant Hose
1 08010001 Standard Grommet 4 Pk

For the rubber hoses, I used standard size barrier hose, but the new reduced diameter hose would probably be a better choice. One advantage of the standard size hose is that most any local hydraulic shop can crimp on AC fittings to your hoses, once you have them cut to the correct length, with fittings in the correct orientation.

The pics below show some of the finished hoses installed.

[Jim Sims]

Standard copper tubing isn't used for vehicle A/C lines (nor fuel lines) due to its poor fatigue life in the vibration environment - it work hardens and cracks plus it is heavy for it's pressure rating. Doc's Bloc's sells the standard sizes of 3003 aluminum refrigeration tubing in coils and straight lengths, plus an assortment of braze-on fittings (propane torch), braze alloy (including handy pre-formed rings for fittings), compressor flange blocks, etc.