A/C Restoration [Long]

[SeaDweller]

Well, as promised, here’s a report on the restoration of the A/C system in my ’78 Euro 911SC. It’s long, but hopefully thorough……….

I’ll admit up front I was quite apprehensive about doing this myself. I planned to get help with the project, but my brother (an ex-mechanic) was unable to assist due to a new job. It wasn’t until I realized it was getting hot here in Florida that I had no choice but to do it. Showing up to meetings soaked in sweat is not very professional, so one Friday evening I made the decision to dive into the project with reckless abandon!

As a precursor, my A/C is an under-dash system manufactured by an Italian company named Diavia. The system consists of the under-dash “package” unit (air distribution assembly and evaporator/blower), and two condensers, one mounted in the rear quarter (fan cooled), and one on the engine lid. The dryer is mounted in the smugglers box. Of course, there are hoses routed all over the place.



Before I physically began the project, I did quite a bit of research on R12 vs. R134, alternative refrigerants, various condenser types, refrigerant conversions, expansion valves, system operation, etc., etc. I won’t go into detail in this area, but I will say that the BBS at ackits.com was an enormous resource. If anyone wants further details in this area, let me know.

I also collected, in advance, all of the parts necessary for the “restoration.” The lid mounted condenser was small and slightly damaged, so I purchased a new, late model lid mounted condenser. The new version has more tubing “runs” through the condenser, and covers the entire grill opening (the original was a smaller, square, Turbo style condenser). I also purchased a new Sanden SD507 compressor (from a Pelicanite), new evaporator fan (directly from Spal US), new rear quarter condenser fan (directly from Spal US), new expansion valve, and new hoses (from ackits.com). The quarter mounted condenser and evaporator were sent to an A/C shop to be pressure tested, flushed, and cleaned.

Regarding the hoses, I’ve seen it mentioned that “hoses are a fortune,” and they are if you buy them from the wrong place. A single Porsche OEM A/C line can run upwards of $200, and my local Goodyear rubber company quoted me nearly $5/foot. I bought 50 feet of line (5/16” and 13/16”), so you do the math. I ended up buying the lines from ackits.com, which came delivered to my door for around $80!!

The system was originally charged with R12, which was poorly converted to R134. With a full charge, the system would cool fairly well, but not good enough to overcome the Florida heat. I realized that this system was similar to the unit in the VW Superbeetle I once owned, and that unit would blow ice! As such, I figured that I had something to work with.

The first thing I did was remove the under-dash A/C unit, which was secured by brackets on the blower assembly, and screws into the bottom of the knee pads. I completely disassembled the unit, cleaned the air distribution housing and vents, inspected the switches, etc. I also completely disassembled the evaporator/blower assembly. I found two “patches” of stuff directly in front of the blowers, which significantly reduced air flow. I sent the evaporator to the A/C shop where they tested and cleaned it.

Next, I disconnected and removed the old compressor. This was a straightforward process. At the same time, I removed the lid mounted condenser, and the rear quarter mounted condenser, leaving the hoses attached.

I then used a razor knife to remove the fittings from the old hoses. The holes through which the hoses route would have made installing pre-made hoses very difficult, so I chose to remove all the old lines, install the new lines without the fittings, and have the fittings installed once the lines were in place. This also allowed for the fittings to be made for ideal, unstressed connections. Pulling out the old hoses was pretty routine. The toughest part was getting all the retaining straps back into position with the new hoses. Routing the hoses required jacking the front and rear of the car up for access to the wheel wells. I wasn’t thrilled with the original hose routings, as they cluttered up the engine compartment, so I made some changes to the routings.

I did quite a bit of stripping, painting, replacing of screws, etc., while everything was apart, and then began the process of reassembling the system. I reassembled the under-dash unit, and installed a new evaporator blower in the process, which has made a HUGE difference in the volume of air the system moves. I’ve come to realize that air volume is a real issue with the factory systems, but my under-dash unit will simply stand your hair on end.

I then installed the new compressor, which came with a very nice aluminum bracket. It took quite a bit of fitting to get the compressor pulley lined up properly, and I had to modify the aluminum bracket to get everything to work. Next came the installation of the lid mounted condenser, which again, was quite simple. I did have to drill a hole in the lid hinge for a mounting tab, which again was pretty easy.

At this point, I brought the car to a local shop that specializes in custom A/C work. I let them install the quarter mounted condenser, because the lines had to be attached before installation. Basically, they installed the quarter condenser, hooked up the fan, installed the fittings, evacuated the system, and charged it.

I chose to go with R12, because I read nothing that would convince me that the system would perform well with R134. What made my final decision was looking at the condenser in my wife’s Honda Odyssey, which has a massive condenser with two large fans. Tons of condenser area with lots of air flow is the only way an R134 system will operate properly, and a 911 just doesn’t have it. There’s an underbody condenser that’s available, but it’s costly, and vulnerable. I wasn’t going to go to this trouble or expense simply to stick with R134. I also ditched the PAG oil, and went with a good quality Esther oil, which is said to be far superior.

The result? So far the system blows ice cold. I haven’t left the car in the sun for any length of time, but I plan to do that experiment tomorrow. I’ll leave it outside, with the windows up, and let it bake in the sun until it’s baking inside. Then, I’ll head out for a test run. One thing I have noticed is that with the A/C on, the engine runs up to 15 degrees hotter. I’m sure this is the result of the lid mounted condenser. The system must have been well engineered for its day, because the refrigerant is first sent to the quarter mounted, fan cooled condenser, where it is cooled somewhat, and then sent to the lid mounted condenser. I’m convinced this was done deliberately to minimize the temperature of the lid condenser.

Well, that’s it in a large nutshell…..By the way, it took about two weekends and five work days (working evenings with constant interruptions) to complete my part of the job. The A/C shop had the car for two days, and the total cost was around $1,500.

[Joeaksa]

Excellent information! Did you have any problem with them swaging the hoses and fitting on for the system? I am going to do the same but have heard that some shops do not have a tool that will install the fittings on the car.

Thanks much and how was the vacation?

Joe

[SeaDweller]

I let the first post get away from me.....Here's some more pictures and descriptions.....


One of the hose routings through the rear quarter. The hose was a snug fit, so getting fitting through would have been a chore.

Nifty aluminum compressor bracket. I had to modify the back of it to get the compressor installed properly.

Tough to make out shot of the quarter condensor. You can just see the 9" Spal fan

Dryer installation in smugglers box

One of the custom fittings. Note the tab welded on and attached to the lid bolt to secure the hose.

Brand spanking new Sanden SD507

[SeaDweller]

The folks that installed the fittings made no mention of having difficulty getting the fittings on. The shop that did my work specialize in the restoration of early Rolls Royces, Jaguar XKE's, and other exotics, so I think they're used to this kind of fabrication and work.

Vacation was fabulous, but definitely not long enough.........Thanks for asking!

[CARRERIC]

Thanks Micheal - Great post! My car has A/C issues as well and I live in Miami. I have to drive early in the morning or at night and still sweat it out. My A/C is still the original from 1975. I am thinking about some updates but would like to keep the vents original.

I'll keep your post for reference.

Thanks
Eric

[SeaDweller]

By the way, something I didn't mention is that air flow through the evaporator is critical for a properly functioning system. Based on the condition of my evaporator (basically clogged), I wonder how many other evaporators are out there that are clogged? A simply evaporator cleaning could make a world of difference.

[Glenntpr]

Really good information. I have a factory installed unit and removed most of the AC components. I left the hoses and now I am looking into installing an under dash unit. Were did you get the Italian Underdash unit? It looks good and almost factory. Thanks for the information.

[SeaDweller]

Wow, this is an old thread resurrected! I haven't visited the forum since I sold my Targa some time ago...

The underdash unit came with the car when I bought it, and it does indeed look factory. The nice thing about the unit is that it actually worked, unlike the factory systems up until the point where they improved the vent system ('86?)...Even with the improvements in the late '80's, this underdash unit would easily outperform the factory system...

I don't know if that particular underdash unit is available anymore...Here's their website, and I don't see Porsche listed:

Webasto - Diavia

For those with early cars, I'd definitely recommend researching an underdash system.