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911 Air Conditioning Upgrade

Pelican Technical Article:

911 Air Conditioning Upgrade

Mitch Leland

Applicable Models:

Porsche 911 (1965-89)

Revised January 2009

Recently (now nearly 6 months later) I decided to upgrade the Air Conditioning system on my "84" 911. I've read and re-read the various threads that have been written in some detailed by some very knowledgeable and articulate members on how they accomplished getting cold air. Primarily these threads have dealt with who's products they used, and the how to's for charging the system. I'd like to pass on my experience with the installation of one particular aspect of our A/C system, the evaporator and the box it comes in. I'll also share my experience of installing Rennaire's ProCooler later in the article.

There seems to be three major suppliers of Air conditioning after market systems for our cars. All three suppliers seem to want to only sell you a "package" with no exceptions. I was told that the suppliers feel responsible if the buyers mix and match parts, then if the performance doesn't meet the owner's expectations they will blame the supplier. I find some fault with this, but the supplier certainly has the right to market his product the way he sees fit. In my case right or wrong I cherry picked what I could get and thought would give me the best temp for the buck. I'm sure this can be argued, but this is what I came up with. I purchased from Pelican Parts Rennaire's evaporator and ProCooler, and from Retoraire I bought their upgraded evaporator blower motor. These parts were available as individual purchased parts. Someone has told me since that Retro-aire has a deeper/thicker evaporator core than the Rennaire. I don't know this for a fact, but size matters here... However I have to say that Rennaire's unit fits the evaporator box perfectly. Again you're limited by who will sell you what... Also I get free shipping and no sales tax from Pelican so there was some cost consideration in my choice.

The installation of either of these products is not rocket science, however the directions that come with these products in my estimation leaves a lot to the installer to figure out. So lets say you've bought and you're installing Retro-aire's new up graded evaporator blower motor. I'll address the Rennaire's ProCooler install a little later.

First and most importantly Retro-aire alludes to either "remove the lid of the evaporator box or remove the entire evaporator box"... Holly Molly this is a giant leap of faith. We better know what we're doing here before jumping into this one line sentence because if you don't it's going to bite ya in your arse.

Option I

Remove Evaporator box "lid only". It seems logical if you're only going to replace the blower motor you would only want to remove the evaporator box lid. However I say it's nearly impossible to remove just the lid that houses the blower motor because of the four spring clips that hold the upper and lower halves of the evaporator box together. In my case I tried to remove the lid only and ended up breaking the plastic spring retainer bosses off two of the four locations by prying the spring clips with a large screw driver. Here's the bottom line, even if you were successful in removing the clips you'll never get them back on with the lower half of the box in place in the smugglers box. I have read that in lieu of the spring clips members have secured the lid to the lower box with safety wire. In my case I have a very low mileage car and this is the first thing that I have broken taking something apart. The plastic has aged and has become brittle, so the option of just removing the lid only without braking something is slim to none in my book. And like I say putting the lid and spring clips back on might even be more difficult maybe impossible, and if you have broken the plastic bosses off that retained the spring clips then anything short of epoxying the lid to the lower box is about all you can do. There is a safety wire fix if everything goes South. See pixs below.

Option II

Remove "entire" evaporator box. If you do this then you're going to have to evacuate your A/C system of refrigerant. Any local Air Conditioning shop can do this, they can store your refrigerant so it's not a deal breaker. Here's the only rub if you do this, now you can consider changing out your evaporator, installing new barrier hoses, maybe a ProCooler, new compressor, Desert front condenser, extra wheel well condensers, replace the engine lid condenser, naturally with any of these changes less the ProCooler you would want to replace the receiver/drier. The point is that once you remove the evaporator box then the rest is pretty easy. You can turn your car into a freezer if that's your inclination. It's just how much money you want or can afford to spend. I think some of this you can creep up on. Even if you have to have your system charged once a year, it might be cheaper than replacing new hoses and a new compressor if you can't afford everything at once. I think getting the evaporator out of the smugglers box is probably the hardest part of the A/C up grades. Once this is done the rest is pretty easy...

One more issue with Option II, you might find after removing the evaporator box that you have some rust issues under the evaporator on the floor of the smugglers box that will need addressing. That's not all bad, and better to know now that later.

Option II - Removal of entire evaporator box and assembly - Details

1. Evacuate the refrigerant
2. Remove any insulation around the refrigerant lines
3. Undo the Thermal Expansion Valve (TEV) line nut - be sure to hold the line with a second wrench or you might twist off the line line as the line material is very soft.
4. Undo the suction line - dittos here, same as item 3
5. Undo two 10mm nuts stabilizing brackets attachments to the body, one on the front left side, one on the rear right side.
6. Loosen 3" hose clamp on top of evaporator lid.
7. Inside the cabin under the passenger foot well toe board remove 4 sheet metal screws on the return air plastic flange. Pull flange out of firewall. You will note that the flange has a resistor pak riveted to the frame of the return air flange. In some cases you'll remove the resistor pak depending on the new blower motor requirements.
8. Now the evaporator and box are ready to lift out.

There are 4 spring clips, two (2) on the front of the box, one (1) on the left side and one (1) on the rear right side of the box. If you removed the entire box as a unit then there's a good chance you can get the retaining clips off and on without damaging the plastic. If you screwed up like I did and broke a couple of the spring clip bosses off in the process of removing the spring clips, not to worry... What I did was to use a No. 6-32 S.S. Truss head (sorry I didn't have the right hardware in Metric) with Nylox S.S. nut (see pixs). In my case I only broke the top half boss so I only had to install the Truss head screw on the top half of the evaporator box. Then to secure the two box halves together I used .030" S.S. safety wire. Also .020" S.S. safety wire would be fine.

Option II - Assembly

More detail on the installation of Retro-aire's upgraded evaporated blower motor. Rock Browning has done a nice job with the mounting of his motor. The mounting board is cut perfectly to fit the upper half of your evaporator box. I do think his directions gloss over some important points.

1. Wiring - Retro-Aire's directions mention that the electrical wiring should come out of the motor at the same point as the old motor. However when I took that at face valve I couldn't get over to the evaporator pipe outlet lid holes on the left side of the box without having the 3 prong rubber wire plug left inside the evaporator box. I didn't like that for a couple of reasons one being an object taking up air flow room that I was already trying to improve upon. So since I had already committed to coming out of the back of the motor I decided to Dremel a hole in the lower half of the evaporator box to accommodate my wiring loom. Now I can drop straight down to a new hole along side the tunnel, slip the wires through a grommet under the carpet and up into the console and rewire the switch at the source. Get rid of the old wiring since I won't be going back to the old fan set up anyway. See item 6 for wiring directions.

In the picture I'm pointing to the new hole through the firewall for the evaporator fan motor wiring loom. This location is along side the tunnel so the wires will be concealed under the carpet. Remember that the old fan motor wires were plugged into a socket on the firewall that has been abandoned once the resistor-pak is removed from the vent opening due to the evaporator fan motor upgrade.

I think in retrospect I would ask Rock at Retro-aire if he could have made up the wiring so there's enough wire to get out of the box on the left side where the suction and TEV lines terminate so the 3 prong plug is outside of the box, not in side... The problem with coming out of the back of the blower housing as I did is that the wiring is jammed into the firewall. However given the choice of not having the plug inside the housing I would probably do it the same way again.

2. Center the motor mounting cradle on the mounting board hole. Drill the pilot holes for the furnished round head sheet metal screws. Epoxy the cradle to the mounting board. Orient the motor on cradle with the furnished hose clamp so the electrical wiring is directed to the exit area of the evaporator box. Tighten the hose clamp. Mount the squirrel cage blower. You might want to put a touch of Loctite on the alan set screw for good keeping... Spin the fan to be sure your clearances are good.

3. Bolt the mounting plate to the upper evaporator box half. In my case I wanted to go back with the factory original evaporator box housing to body brackets that Retro-aire doesn't call for. I used a 1/4-28 nut plate and riveted it to the underside of the plastic mounting board. I only used two nut plates since there are only two exterior brackets. The other two attachments I used S.S. bolts and nuts.

4. Right now before you get much further the directions neglect to mention that you need to drill a hole for the capillary tube through the new mounting board. You need to do this so you can insert the capillary tube through the top of the evaporator box and slip it down through the fins of the evaporator. This would be a good time to drill the hole and burrow a path through the fins for your capillary tube.

5. To re-install the entire evaporator box you have to hold your tongue just right to wiggle the box down into the smugglers compartment. However some of the alignment of the condensate drain pipe will have to be done from inside the car by reaching through the return air vent opening at the foot well. You can take a wooden dowel and carefully pry and move the drain tube towards the hole in the bottom of the smugglers box to align the two. It might help to have a second set of hands at this point. Once the drain pipe is aligned with the hole in the smugglers box the entire box will settled in. It's a tight fit at best... I found a piece of 3" neoprene hose which is tight since it's a metric size. I wanted a smooth I.D. hose. I nipped the ends of the hose in about 3/16" to help get the hose started over the pipe, lube up the interior with silicone grease, slid the hose as far as I could onto the manifold that was in the car, then pulled the hose back over the evaporator box once it was in place. It wasn't that easy, but doable.

6. Rather than cobbling up the existing wiring with the new wiring I just lifted the console and ran the 3 new wires up under the carpet and into the console. Pulled the old spade clips off of the high, med, low male spades on the back of the A/C blower fan switch, replaced the new wiring that already comes with the correct female spades ends. I looked up in the Bentley's wiring diagram for my model year for the color code: in my case the the color code for my "84" model was as follows:

Factory - Low = red/grn - Retro-aire - Yellow (you remove the red/grn factory wire and insert the new yellow.) Factory - Med = red/blk - Retro-aire - Red Factory - High = red/wht - Retro-aire - Orange Retro-aire - black to ground - I used the rear stabilizer bracket to body mounting stud in the smugglers box for the ground.

Right hand picture: lower LED lens (between the two knobs) is the Griffith's A/C indicator light, when the A/C fan only is on the LED is green, when the compressor is on the LED turns orange. It's a nice addition to the system so you always know what mode your compress is in.

FYI: The second LED light above Griffiths compressor cycle light was my attempt to install a red blinking monitor light for the factory alarm system. I thought that would be easy, Naaah! The best minds couldn't figure how to do it...

7. Rennaire's motor and motor mounting bracket is well done. The motor runs on high speed as quiet as the factory fan motor was on medium. It also blows more air. I'm sure part of this is the fact that the resistor pak is removed from the return air duct.

Install Rennaire's Evaporator - Purchased from Pelican Parts.

Once the evaporator box is out of the smuggler's compartment it's pretty much a drop in... The only hiccup I had was the two pipes (TEV and expansion lines) that come out of the box were further apart than the stock factory evaporator so I had to Dremel out a wider opening in the top half of the box. Not a big deal. You also will want to be sure that you have provided a path for the capillary tube through the fins of the evaporator before you have installed the evaporator and blower box into the smugglers compartment. Here's a good thread on inserting the capillary tube.

Griff of Griffith's told me that you want to bury 3 1/2" of the capillary tube into the evaporator box.

Make sure that you install the suction line onto the evaporator first, then the TEV line last. If you do it the other way around you can't get at the suction nut to tighten it. See picture for clamping the copper coils again the suction line.

The TEV (Thermal Expansion Valve) that comes with the evaporator is for R134, Rennaire told me even though I was using R12 the R134 TEV was OK. If you have any questions about this be sure you find out before buttoning up your project.

Installing Rennaire's ProCooler - Purchased from Pelican Parts.

My thought was that my A/C worked, but not well enough to stay ahead of the Texas heat. I could get 55 degrees vent temp with 90 plus degrees outside ambient temps. I wasn't too keen at this point to install extra condensers in the fender wells, I had a good compressor, my hoses were good so I went with Rennaire's ProCooler. At this point I decided to stay with R12. I had a source for R12 so cost wasn't an issue and my system was fully charged.

You'll need to buy a bottle of "ester" oil to lubricate the new "O" rings before installing. It's cheap, however one bottle could lube 1,000 "O" rings. I Don't know why a small bottle isn't included in the package.

1. Installation of the ProCooler - The directions were tough for me to get into. Between two of our members I've included the most important piece of information you'll ever need to install the ProCooler. Unfortunately I can't remember who posted the original picture showing the ProCooler with his fender off the car. I apologize in advance for using the picture. Member "Rusnak" was good enough to add the graphics to help me out with identifying which line went where. Once I saw Rusnak's graphics it became instantly clear of where the lines went. The job isn't really that hard, it's just the directions or lack of them that made it hard.

2. The biggest problem for me with mounting the ProCooler is routing the hoses and the canister for tire clearance. I have 8"X16" front wheels. You need to rotate the canister clockwise as far as possible and get the canister as high in the fender well as possible for clearance. In my case I removed some clamps under the car on the existing hoses to gain some extra length so I could raise the canister higher in the fender well. To accomplish this I took a bottle jack with a 2X4 block on edge, padded the 2X4 and placed it directly next to the bottom fitting and jacked lightly so the canister and all the attached hoses were elevated to their highest point on the mounting bracket, then tighten the hose clamp. Otherwise you couldn't get enough force with one hand and tighten with the other to get the job done. It doesn't take much pressure with the jack to do this...

3. Suction line. The ProCooler kit comes with a 12" add on piece to extend the existing hose from the compressor/suction hose to the ProCooler. The existing hose has a 90 degree elbow and with all the fittings looks pretty cobbled up to me, because of that I had a new line made up that ran from the compressor to the ProCooler. The new line was 13'-4", probably 13"-2" would have been enough... I did a lot of calculations on the revised length, but never verified what was in the engine room. I think I had too much hose in the engine room. This maybe was because you need the extra length when you remove the engine and rest the A/C compressor on the rear fender. My local parts house made up the new hose. The hose cost $62.00.

On arriving at the local garage to charge my system I found that once the car had settled on the struts the tire was rubbing on the hose that connected the ProCooler to the evaporator, albeit ever so slightly. So I took the car back home and reworked the hose routing and the canister rotation. This was now my 2nd attempt at getting tire clearance. I'm not sure whether it's the 8"X16" wheels, or the 930 wheel off sets, but it wasn't giving up easily.

4. I might add don't be too quick to re-install the skid plate over the torsion bar because it took me a couple of tries to figure out how to route the hose from the expansion valve (TEV) to the Procooler.

5. I filled all the old screw holes down the passenger side of the floor pan where the hose clamps had been with black silicone. I had to install 3 clamps across the engine firewall at the floor pan for the re-routing of the suction hose up the driver's side of the floor pan. I used tie wraps to join the two A/C hoses so not to put any more holes in the floor pan. All those holes and screws transmit noise into the cabin so I wanted to minimize the intrusion of that.

The red rubber cap on the above picture is the sight glass, old school says that when you charge the system and the glass runs clear your system then has enough freon. That is how Jones' Autowerks charged my system. It might have well worked out, in fact it did blow 30 degrees at the vent until the evaporator froze up. Later I determined I had a bad thermostat switch and or capillary tube, at that point it was the only thing left... However undercharging can promote the evaporator freezing.

Summary of Cost:

FYI: The new Suction-Low pressure hose from the compressor to the ProCooler - 13'-4" from Center line of 90 degree elbow to very tip of the straight fitting.

1. Evacuate and charge (additional 6 oz. R12 and oil with dye) - $89.89
2. New suction hose (compressor to Pro-Cooler) - $62.00
3. Ester oil, large roll of insulation tape, black enamel, hardener - $65.22
4. ProCooler and Evaporator - Rennaire products from Pelican - $583.25 (no shipping, no tax)
5. Evaporator upgrade blower motor - Retoraire - $219.00
6. Jones' Autowerks - Fabricate new hose, install sight glass, re-route hoses, charge system - $477.06
7. Griffith's Technical, Inc. - Kuehl AC Indicator Light, AC Thermostat switch - $143.00

Total - $1,638.53

In summary, my first R12 Freon charge was with my local A/C guy who is more comfortable working on John Deere tractors and Diesel trucks than Porsches so he's not an air conditioning specialists by any means. I didn't have any leaks when he evacuated the system so that made me happy... After the local guy charged my system I was still getting evaporator freeze up. I attributed this to an improper charge. So I made an appointment with Jone's Autowerks in Santa Antonio. There we discovered that I still had a tire interference problem with the A/C hoses at the ProCooler. Jones's Mechanic figured out that the Rennaire's hose from the TEV to the ProCooler needed to be longer to be able to move the ProCooler canister higher in the fender well. Fortunately Jones had all the fabrication equipment for new hoses and while we were there we added a sight glass ($27.00) which allows you to see if your system has Freon, all of this was money well spent...

My big hiccup was not recognizing early on that I had bad a thermostat switch. But given the outcome I'm pleased with what I've got. I know there's more to be had with more condensers, changing out the existing front and rear condensers for contemporary serpentine condensers, etc.

Presently I'm getting 30 degrees at the vent on 85-90 degrees outside temps with the thermostat set midway on middle setting of the fan. The A/C goes off at 30 degrees, temp runs up to 40 degrees, the A/C comes back on and the dance goes on. If I would have recognized my bad temp switch early on I would have been in to my upgrade for just a little over $1,000. While my system might not be a rolling "sub-zero" refrigerator, it does a great job in all but the worst days of our Texas summer days. So I think it's a lot of temp for the buck, and I can add on to my system in the future as time and money allows.

I might add that I think Griffith's variable speed evaporator fan switch would be a nice addition to a good working A/C system. I found that times even on low speed I was putting out too much cold air, but the outside air was still too hot to use the vent setting. When time and money allow I'll add the variable speed switch.

I'm not an expert, but a DIY'er and wanted to share my experience. I know there's many different ways of accomplishing the upgrading of the air conditioning of our cars. I hope the attached information helps another lost soul that's looking to be cool...

Most of the products in this article can be bought through our host.

"Home in the Hill Country"


Comments and Suggestions:



RennAire Porsche 911 Air Conditioning Products


YESR 1987

July 12, 2016
  Followup from the Pelican Staff: I am not the best with part prices.

Give our parts specialists a call at 1-310-626-8765
- Nick at Pelican Parts
wwest Comments: The procooler, at best, has no effect on the performance of our A/C systems, at worse, a NEGATIVE effect.

Yes, the procooler can be used to lower the temperature of the liquid refrigerant in the R/D, but what comes in must go out.

First, there must remain cooling capability downstream of the evaporator, meaning the TXV is failing its job. Once the evaporator is chilled as low as possible absent being subject to freezing up, the TXV should be seriously THROTTING the level/amount of refrigerant entering the evaporator volume, thereby leaving little or no cooling capability downstream of the evaporator.

Additionally, should there be enough cooling capacity to cool the R/D liquid "store" the procooler transfers HEAT from the liquid to the suction side gas, increasing the burden on the compressor/condenser.

The procooler concept is only pertinent for systems that use an EPR to regulate evaporator cooling level.
August 27, 2014
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
lenny Comments: so what do you think was the biggest improvement ?? the evap. or the pro cooler ??
April 28, 2013
  Followup from the Pelican Staff: I don't want to speak for Mitch, but reading the article it sounds like the pro-cooler gave the boost he needed to keep up with the Texas heat. - Nick at Pelican Parts  

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Page last updated: Wed 1/17/2018 02:16:02 AM