A/C upgrade questions...

ascarswell · 05-20-2005, 09:49 AM

I have a '79 911sc w/ factory air that has NOT been upgraded. (I assume, then, that it is the old R-112 with a piston compressor?) What do I need to upgrade it and make it more effective? Do I just upgrade the compressor to a rotary one, change the dryer, and recharge with R-134? I know it can't possibly be that simple, can it!?!?

How much should I expect to have to pay, in total, and how much of an improvement should I notice with the upgrade?

Summer in Florida is killin' me!

Thanks for any input

Cheers,
Adam

Hugh R · 05-20-2005, 09:56 AM

Do a search on A/C, there are one or two threads on this right now that are active. Do a search on Jim Sims, he's the A/C God around here. Jim would suggest purging the old R12 if there's any freon in it. After pulling a vacuum, see if it will hold a vacuum for about an hour. If so, go to Walmart, Kragen, etc. and get a R12 to R134a conversion kit, make sure you put the R12 to R134a oil in (it comes in a can that you suck in like refrigerant, or get the oil and 134 mix and introduce it. If it cools, your good to go. You can always buy a new compressor later if its seized, leaks, etc. You can buy the kit for around $20-$30. You can buy cheap vacuum pumps for Harbor Freight that work off of a compressor. Or see if another Pelican in your neighborhood has a vacuum pump. I found another Pelican a mile from me with the vacuum pump and gauges.

scottb · 05-20-2005, 01:03 PM

Hugh's suggestions, especially about Jim Sims, are good ones. It really depends on what you want. If you just want cooler air, then purge the system, pull a vacuum, and fill it with R134a. You probably will get thru the season with cooler air coming out of the vents.

If you want cold (i.e., sub-40 degree) air, you'll need to do the following:

1. Get rid of the York compressor. Very inefficient. Vertex sells a Sanden with an adapter plate for the 3.0 engine. I think Rennaire sells a Nippondenso with an adapter plate for the 3.0. The Nippondenso is the factory compressor for 84-89.

2. Replace your original hoses with barrier hoses. Rennaire.com sells a kit for $369.

3. Add condenser surface. I put a fan/condenser assembly in the front left fender.

4. Add a subcooler. Hugh made his own. I bought mine from ProCooler.

5. Open and clean out the evaporator and its box.

6. Once the system is buttoned-up, pull a vacuum. Assuming it holds a vacuum, take it to an a/c shop with 911 experience, and have them charge it with R12. An a/c shop with 911 experience will know to have the car idling at 2000 rpm, and to do the charge with the rear deck closed.

So, you have some decisions to make. It's a tough call...spend a few bucks and limp thru the summer, or spend $1500-2000 and do the job right. Good luck with your decision. Let us know what you decide.