Project Summer Comfort - Refreshing factory A/C

[dmarier]

...."I have no idea (not being well versed in heat transfer and other thermodynamic topics) whether running 17 smaller tubes instead of 9 larger tubes will add more heat transfer capacity or not. It seems to me that it might. So this could be a good thing for function as well as just being new and more reliable."...


Take it from a Chemical Engineer....the heat transfer will be better.

Dan Marier

[Arne]

Thanks, Dan. I thought that should be the case, it just seems to make sense. But since I know a bit about what I don't know—and this topic is totally outside my expertise—I didn't want to make false claims.

[govols!]

Thanks, Arne, for the step by step analysis and install !!

[frederik]

The 17 smaller tubes have more surface area, so it makes sense that this transfers more heat.

[Arne]

While I wait for the remaining parts to arrive (ETA still Tuesday), I spent some time test fitting the original front condenser and rock guard so that I'd have an idea of what I was up against when the new condenser gets here. Test fitting turned out to be a good call, as I learned several things:

1.) The two mounting holes with captive nuts in the suspension pan on the right side are not in the proper spots. The suspension pan was replaced before I took possession of the car. Replacement pans do not have those holes marked or predrilled, the installer needs to do that. In my car's case, the installer missed the spot—both right side holes are about 20mm (¾") too far forward. I can deal with this in one of two ways. I can either drill a couple new holes in the proper locations (ugh!), or I can fabricate a small bracket with new studs that will bolt to the misplaced holes. Neither option is ideal, as I'd prefer not to drill more holes in the pan, but the bracket will drop the right side of the condenser down about 4-5mm, and the dang thing is already low enough. Will put off this decision until the new condenser arrives.

2.) The steel mesh rock guard needed a little help, it was a little bent here and there.

3.) As I mentioned above, the condenser definitely hangs down in the breeze. The bottom of the rock guard sits about 45mm (1¾") below the bottom of my car's standard bumper. I don't think this should be a road clearance problem for any attentive driver, but it is very visible. In hindsight, this would have been a good reason to upgrade to an S bumper when I painted the car, as the S bumper is a bit deeper and would hide it a little better.

4.) Even though I don't anticipate dragging or curbing the condenser, I'm still thinking about possibly adding some protection, just in case. The factory installed a pair of nerf bars that mounted to the suspension pan at the front control arm mount and extended up to the front bumper guards. Like the condenser and rock guard, they weren't what you might call attractive, but look like they could protect from accidental parking curb damage. I've been running without bumper guards (removed and discarded by a prior owner), but I might put on a pair if I could find a straight pair of the nerf bars. Their part numbers are 911-505-141-00 and -142-00, and are (of course) NLA from Porsche. If any of you have any of these bars that are not bent up sitting on a shelf somewhere, send me a message. (Example picture from BaT. This VIN of this Sepia '72T is only 2 cars later than mine.)

[Arne]

The remaining parts arrived today, one day earlier than expected. I've unpacked it all, and it looks really good, very complete. Will begin by mounting the front condenser and new compressor, then begin routing the hoses. The hose part will take a little extra time in that since I didn't remove them myself, I've never seen them installed on this car so I will need to look for clues on the exact routing. But I'm thinking I should easily be able to get this all installed this week, so tomorrow I'll call my A/C shop to set up an appointment for next week to get it evac'd and charged. The only thing I need to acquire now is a drive belt.

[skinnerd]

Looks great Arne. Watching all your progress with great intent. Ha
I might go the electric AC route in my early 911, but I understand your vision and respect it very much.
Looking great!
I'm from Oregon also and that was some very hot days for sure a couple weeks ago.

[Arne]

Looks great Arne. Watching all your progress with great intent. Ha
I might go the electric AC route in my early 911, but I understand your vision and respect it very much.
Looking great!
I'm from Oregon also and that was some very hot days for sure a couple weeks ago.

If my car had not been a factory A/C car, I'd have given some serious consideration to the electric A/C. But rehabbing a system that the car was built with would seem a lot simpler than starting over with a different technology... probably.

[Arne]

More progress today, although I've run into a few little fitment issues.

At the front condenser, I decided to drill new holes in the pan rather than use an adapter bracket. I felt that I really did not want to have the right side 4-5 mm lower than it needs to be, and uneven from side to side. This was definitely not Griffiths fault. I also had to trim and tweak the debris guard cage a bit, to give adequate clearance for one of the hose fittings. A little hard to blame Griffiths on this one either, as the debris cages all seem to get beat up over time, and I suspect that all of them fit slightly different. In any case, that condenser is done. Not quite a "drop-in" job, but not bad either.

Mounted the receiver/dryer in the left front wheel well. No issues at all, and they even supply a pair of new metric hose clamps to mount it.

The compressor is in place, although not completely cinched down yet, as I need to be able to set it on its side so the oil doesn't run out when I connect the second hose. The Sanden-type 507 compressor is a really tidy little package. And the new slider mounts Griffiths provides are very stout, well finished parts. Not to imply that everything is perfect, however. To get the belt grooves on the pulleys to line up, the upper part of the bracket needs to be slid or adjusted all the way forward. But when slid that far it interferes with the vacuum port on the MFI stack. This would be a problem on any '72-73 MFI car (plastic stacks). I don't know if a similar issue would be true with earlier MFI cars (mag stacks) or carbs. Definitely something to watch for, however. I cut a small relief in the sliding plate to eliminate the interference point.

Last thing I determined is that the stock size belt (variously listed as 13x1100 or 17435) is a bit too short. I will be exchanging the one I bought today for a longer belt. Will report the correct fitment soon.

Tomorrow? More fun with hoses...

[Arne]

Exchanged the drive belt today. The size that works is 17445.

Worked on routing hoses for a while this afternoon. Going OK, but still takes some effort and fussing. I have 3 of the 5 hoses routed and connected at both ends. Two of those will still need a little final securing, but I want to wait until everything is in place before finalizing that.

The routing and securing work is more or less what I expected. This although one of the things I was hoping for with the "standard" diameter Griffiths hoses does not apply to early cars that came with the red hoses. Turns out the original red hoses are smaller outside diameter than today's "standard" hoses, but larger than today's "reduced diameter" hoses. So all the clamps need a bit of massaging to work properly. Oh well...

I have an appointment next Tuesday to have it evac'd and charged. Should be no problem at all to have it completed by then.