yet another ac experiment
 

Well, the results are in. Long live marginal AC! I can say it was better than before (ie blowing air that was ambient temperature), but that isn't saying much. This of course was a fairly low budget attempt to get the system working.

Replaced the factory York with a new Sanden. Replaced the receiver/dryer (old one was totally plugged). Replaced the expansion valve (old one was fairly gunked). Didn't do anything else...all original tubing, condenser, evap, etc. System held a vacuum so there weren't any gross leaks. Charged with Freeze12.

Sooo...getting around 50 degrees at the dash vent. Not exactly icy. But the good news is the Sanden doesn't seem to tax the engine very much, and I at least can get some cool airflow in the cabin at a dead stop. I think I'm done throwing money at the AC for awhile...any next steps would involve significant chunks of change, and I need to do a few other things.

Mine is stock & the PO got it charged pretty regular. I haven't checked the temp. but it does make things a bit more comfy on the few hot days we get around here. I was enjoying it today after work when a 89 cab blew buy me. :eek: As long as I keep the system charged when I starts to go flat & run it periodically will it keep going? Or is there something I can do to help preserve it. I wish I could just yank it out but I want to keep the car original.

nostatic,

How did you determine how much Freeze12 to use? Have you tried "playing" with the amount of charge (add a little, let the system equalize or release a little, let the system equalize)? I'm not familiar with Freeze12 but the amount of coolant can have a drastic affect on cooling. A couple anecdotes: When I converted my 951 (a few years ago) to 134a it took me 3-4 days of trial and error (driving every day with a digital thermometer in the vent) to get an optimal charge, I eventually got down to 45 degrees (so your 50 isn't so bad). Further, "back in the day" we had a '79 Coupe de Ville that needed "topping up" every spring, I had it at a local, oldtimer, friend of the family, mechanic's shop one day, using his gauges to be sure I had the proper fill in the system (the dealer never got it to cool right). I complained that it had never cooled very well, he took one look at the gauges and told me to put in at least another 8 oz. of R12 (it seems the repair manual, which I was following religiously, was wrong). I followed his advice and after that you could store meat in that car, it would absolutely freeze you out.

Good luck,
Jerry M
'78 SC

From my countless, expensive attempts to get A/C working well in old cars, all I can say is that I could not agree more with you, Jerry. :cool:

It was added per guages. I had hoped for a bit cooler, but the parts replaced were ones that were shot, so it wasn't a complete loss. I actually want to modify the compressor install a bit (spin it 90 degrees), and the short hose from compressor to condenser needs to be replaced/redone....it is a kludge right now because the original didn't have much stretch in it.

anyone ever took one from a 944 and put it in the 911? my '88 944 blows too cold smoetimes...

Nostatic - What model number Sanden did you purchase? I'm putting my own update kit together and am curious what the number is on your Sanden.

BTW - I think you need to go with barrier hoses if you want to use anything other than R12.

If the OEM R-12 hoses are in good condition and not leaking at the fittings they can be left in place and used with R-134a; the mineral oil used with the R-12 systems has coated the inside of the hoses and greatly reduces the permeation of the R-134a. Since the mineral oil is not miscible in R-134a is stays in place on the interior of the hoses. If a hose is leaking it should be replaced with one of the barrier type construction. It is a bit of dirty work to pull and replace hoses plus there is the expense of buying or making the hoses so if the R-12 hoses are on good shape I'd leave them alone. Jim

I just completed the same conversion as Nostatic last weekend. Sanden compressor, new drier and Freeze 12. The vent temps today were at 58F with an Ambient of 90F. Somewhat disappointing but perhaps the expansion valve is clogged, it made a squealling noise for the first few minutes but has since settled down.

I also removed the bowtie vent, the improvement in air flow was well worth the 60 seconds of time.

Either of you have the Sanden Part number off the unit housing?

Looks like SD507 on the invoice.

Looks like another vote to disconnect.

I just put a new Sanden compressor and a center vent on mine and I am chillin, it's working great with a stock system. I'm getting 30 and 40 degree temp's when it's on it's coldest setting.
I was just out and turned the temp setting about mid way as I was too cold. I'll check it again tomorrow when it's good and hot out.
I had TRE do the work but would guess like was mentioned before it's a proper charging issue. It also might help to blow the condensers out with air to clean them of any dirt.

I was also wondering what temps SC's/ Carrera's got from the A/C when they were new cars. They had to work pretty good I would think?

One thing I noticed is my temperature knob has no apparent effect, so that might be part of my problem. Given a couple of other things I need sorted, I think I'll be calling TRE on Monday (and won't bring my own parts).

Could a temperature faulty swith can cause the a/c system to cool not enough? My 1972 911 have a rear condenser with 2 auxiliary electric fans blowing to the inside of the engine compartment and an extra condenser with electric fan located in the rear fender. The system is working with R 134a. The compressor is a Sanden 507. New expansion valve, new barrier hoses, new filter/drier. Original and clean evaporator. The a/c temparature is cold but not very cold. My brother 911 Porsche cools more that mine. It have a rear condenser and a Sanden compressor. The temperature (thermostat) switch can cause that?. I have a modern evaporator/blower unit system from other 911 Porsche that blows more air, but to install it I will need to do some modifications. This can help to solve the problem?

My bone stock SC put out 36 degree vent temperature on a 85 degree day, but I'm still using R12.

I have a Seiko-Seiki compressor, and new drier reciver ready to replace the old York, but until the York breaks I just enjoy the a/c. Who knows, I may get a turbo and use the Seiko-Seiki for that.

Temperature knob controls the cycle for the compressor. Put it on the coldest setting if you don't want to have the compressor constantly cycling. By having the compressor run longer, the evaporator should become colder and the air passing thru should be colder.

It's not an instant on type of switch, just set it and forget it.

Well I did a re-test on the A/C today. It's about 95 degrees out and there's no traffic so I wasn't sitting and ran the fwy and surface streets about 50/50 for about an hour. The coldest the lower vent temp got was to about 48/49 dregrees on the coldest setting. And was in the 50's after a stop but came back down to about 50/51. I'm using a probe type a/c temp. tester.

My oil temp got up to about 225 after a stop. Not quite half way between 210 and 250 on the gauge and about as hot as I've seen it since I put the 28 row brass cooler on. Most of the trip it sat on 210.

I was comfortable the whole time but don't think a trip to the Desert would be to fun on a day like today :)