Project Summer Comfort - Refreshing factory A/C

[tfiv]

Cool project. I got a copy of Rob Siegel's book "Just needs a recharge" recently. I would reccomend it.

[Arne]

"Just needs a recharge..."

Yeah, right. These early systems before the advent of modern barrier hoses always needed a recharge. I had all the service records on my previous '84 Carrera from new. (Yes, all 8 prior owners saved all the receipts. What are the chances of that?) I went through them all and saw that the factory A/C on that car was recharged 4 times in the first 3 years. After upgrading the hoses (and evaporator and front condenser) I went the final 5 years of driving without a recharge, and it was still working fine when I sold it. I'm expecting the same for this system.

[tfiv]

I have an old truck (R12) that before I quit using it with any reguarity (years ago) would need a bi annual top off. Not really caring about the system (or really the truck) I charged it with keyboard duster air (aka 152a) for fun. Blows 38 degrees, and I don't have to feel guilty about it gradually leaking out. Ya I know, mildly flammable...

[blucille]

funny, I did just the same as Arne, 4 years ago to blucille, my dealer installed '72, hot rodded in the mid-late 70's....I updated the AC compressor, evaporator and blower, (parts from Griffiths) but left period hoses, old condenser, Filled it with R-12 and that was 4+ years ago. Hasn't needed a topping-off....blows ice-cold, even in LA traffic.

Actually, it does work better than my fully Griffiths equipped BLACK on black 83 SC, that car has the FULL 4- condenser system from Griffiths, (left rear fender has 2 condensers with fans--one in front and the other behind the wheel)....Giff calls it his ICE package, all new barrier hoses but the R-134 just doesn't do as well as the R12 in blucille.

[Arne]

I think the biggest issue with the '76+ cars is the serious lack of vent area. The little vent in the center of the dash plus the bow-tie for the footwells simply can not get enough cool air into the cabin. I'm hoping for better results with the 6 vent under-dash plenum system in the '72. And I won't rule out having it charged with R12, either. Will definitely discuss that with the shop that I have do my A/C work.

[Arne]

The upgraded evaporator and blower motor arrived today, as expected. First impression was really good. And then I read through the detailed instructions. Extremely thorough. The kits come with everything you need. Far nicer than the parts I used on the Carrera.

Cleaned everything up, and started on the installation. The hardest part was getting the squirrel-cage off the old fan motor. Once past that hurdle, everything I ran into was addressed in the instructions.

One thing to note - there is no going back to stock on the fan motor, as you need to modify the motor mount plate. I can't image why one would want to revert, but it is worth mentioning. Also, most evaporator boxes will need some very minor mods as well. Again, well documented.

I called it a day this afternoon, as the garage is hot, and I got to a good stopping spot. The evaporator box is completely installed, sealed, and the fan is tested. Tomorrow I will finish this part of the project with inserting the thermostat tube and connecting the evaporator box to the vent plenum under the dash.

I failed to take a picture of the fan motor...

[Arne]

I wrapped up the evaporator box part of the project today. Found the first thing that Griffith did not get right so far. The evaporator kit includes all manner of fiddly bits that are needed to get this done right. Things like screws to use to hold the box together instead of the spring clips, a new brass tube for the thermostat sensor, etc. One of the included bits is a new hose to connect the evaporator box outlet to the inlet of the vent plenum. And the one provided is too short by about half. My suspicion is that the shorter hose may be correct for the later cars with the center dash vent, which obviously comprise the bulk of their sales. Also remember that this part was off-the-shelf from Pelican. It is possible that if I had ordered it direct from Griffith, a longer hose might be packed when they know it is for an early car.

In any case, I took the original hose and cut off both of the frayed ends, then used the middle part to extend the new hose from Griffith. Works fine that way.

Then I tested the fan and airflow through the vents. Really happy. This motor has a fair amount of rumble noise on high speed, just like the original motor for this car was, and also the original in the '84 Carrera. Low and mid speed noise levels are quite fine. And with the new higher output motor pushing air through the six vents, there is a lot of airflow. I may not need high speed very often.

Next up will be the new rear condenser, ETA is Tuesday.

[Arne]

The rear condenser is running late. FedEx spent 2 days bouncing it (hopefully not literally) around Los Angeles, it made 3 stops there before it actually left So Cal. And then instead of heading north to Oregon, they routed it east to Las Vegas, Salt Lake, and into Idaho. Might be here tomorrow. Maybe.

Griffiths shipped the compressor kit and front condenser today, almost a week earlier than originally promised. So I should have everything by the middle of next week. I might actually be able to get this done in time for the next PCA drive on the 24th. Might be a few long days running hoses...

[Arne]

FYI - Based on combined shipping weights of all the various parts, plus estimates of the weight of the vent plenum and compressor brackets, the total weight of factory (2-condenser) A/C in an early 911 is 75-80 lbs (34-36 kg). Maybe 80-85 lbs (36-39 kg) if you still have the original York-style compressor.

[Arne]

The rear condenser finally arrived today. And it is good. Fits correctly, proper fittings and hose orientation.

Remember this statement of mine from earlier?

Most of the rest of the parts will also be replaced and upgraded, other than the deck lid condenser. I will re-use that part, as new ones are not functionally better.

Turns out I may have been wrong. The new condenser might have higher capacity than the original.

The original was part number 911-573-057-00, normal tube-and-fin construction, with 9 tubes going through the fin pack. PET shows that part number was superseded by 911-573-057-02, which was used on impact bumper cars through the end of '83. The newer part number is what Griffiths and other all vendors offer.

Turns out the difference is in how many tubes criss-cross back and forth. The new condenser has 17 slightly smaller tubes, almost twice as many as the original. The overall dimensions of the unit are the same.

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.

The remaining parts have an ETA of next Tuesday, assuming FedEx Ground doesn't play games with them as well.