A/C, what do I need?

[Nick Triesch]

Well, it is the start of Summer and my A/C blows warm. Compressor works, refrigerant just leaks out slowly over time (a few months) . I checked my records and the unit has been checked and serviced and repaired from many shops over the years only to stop working again and again. I would like to take a crack at it. Please advise what equipment I will need and about how much it will cost to put on a vacuum and such. I know my unit will not make ice but I would like just a liitle bit of cool for a trip or two. Went up to Julian California for breakfast this morning but by 11.00 AM it was about 100 in a black Carrera! Thank you. Nick

[DWeg1998]

I'm in the same boat. Anything over 80 degrees and direct sun light and my AC feels warm. Lower than that or in the shade and it can keep up. I just had it serviced and everything it working as it should, which means barely working. I think next summer I might plunk down some money on upgrading this. I understand the compressor is the short coming in the system.

[Fsquad]

I have an 82 and I am also trying to decide what to do about the A/C. Parts alone look like $1500 to up grade. I am sure I will have $500 in getting the existing to work again. From what I have read here the original never worked that well in the first place. I do not want to up grade only to find that the new system does not work very well either. Their must be folks who have done this out there who no. Any info will be greatly appreciated. Thanks, Tom

[kuehl]

Nick,

Assuming you have a black 85, and you obviously know you have leaks and the leaks have not been fixed. You need to find the leaks.

First, I'd gather the previous repair orders and let us know what parts if any were replaced. This would save a lot of second guessing by the board members as to how to approach the fix.

Second, you can do a quick visual inspection of the common places, such a compressor nose seal tossing an oil line above the compressor pulley on underside of the deck lid. Look at the fittings on the deck lid condenser where the hoses attach to see if there is any oil residue or if they were ever brazed. Inspect the hoses under the car starting in front of the rear tires on each side for signs of 'crushing' from lift pads. Look at the hoses at the drier to see if there has been a tire rub on either hose.

There are quite a few threads here on DIY evacuation and charging and where to buy affordable equipment, there is a range in prices and naturally you get what you pay for. But you never know when a fellow car owner might chime in on your thread here an offer an hand. "Experience" does make the process less frustrating.

[T77911S]

if you dont find anything as kuehl has suggested and all the Orings have been replaced and still no luck, its the evap. the only way (that i know of) to check it is to use a sniffer and check the vents, or just crap shoot and replace it along with the expansion valve.

[wwest]

Originally Posted by Nick Triesch

Well, it is the start of Summer and my A/C blows warm. Compressor works, refrigerant just leaks out slowly over time (a few months) . I checked my records and the unit has been checked and serviced and repaired from many shops over the years only to stop working again and again. I would like to take a crack at it. Please advise what equipment I will need and about how much it will cost to put on a vacuum and such. I know my unit will not make ice but I would like just a liitle bit of cool for a trip or two. Went up to Julian California for breakfast this morning but by 11.00 AM it was about 100 in a black Carrera! Thank you. Nick

I have a theory...totally unproven.

What if, once you shut the engine off after a hot day of A/C use, rising engine heat results in the already high pressure refrigerant in the high side/condensor rising high enough to ovecome the factory O-ring seals..?

An "after-run" blower/fan?

[kuehl]

West,

Didn't you already run through your theory by attaching pressure gauges?

Slippery AC Slope

If you were to put fans under the deck lid for the 'after run' you would have to invert the fan blades for each direction you wished to move the air towards..... not practical.

[GH85Carrera]

To answer the original question, what do you need for AC?

Call Griff and discuss it with him on the phone. You will learn a lot and he can determine what will fill your needs. I did the Dual Kuehl upgrade, new hoses and new evaporator several years ago. It was some of the best money I ever spent on my 911. Oklahoma gets HOT in the summer. Before the AC upgrade I avoided driving my 911 if it was 100+ outside. I have driven to both coasts and been in some HOT places and my system flat out worked.

Last summer I drove to Savannah GA in AUGUST! That place makes Houston look balmy. One day the heat index was 125! It is a beautiful place but HOT. My wife was with me for the trip and one day on a tour she actually got cold in the car and asked me to turn the temperature up! My dream come true for 911 AC. On the trip home one day one we drove due west for 900 miles into the sun on a 100+ degree day. After many hours in the blazing sun the AC was maxed out, but we were comfortable. The engine temps were lower than when I had stock AC system.

Griff's prices are not cheap, but his quality and product engineering is top notch good solid quality. I don't expect to get top quality anything for bargain basement prices. When I pay the price I expect top quality and I got that and the best tech support possible. I feel sure Griff rolled his eyes a few time with my incessant questions about AC theory and operation. I learned a lot and enjoyed the process and the result.

And in case any of you are wondering, yes I paid the full retail price for my AC system. I am just a very happy customer that is impressed with his quality design and product.

[wwest]

Originally Posted by kuehl

West,

Didn't you already run through your theory by attaching pressure gauges?

Slippery AC Slope

If you were to put fans under the deck lid for the 'after run' you would have to invert the fan blades for each direction you wished to move the air towards..... not practical.

First, with a standard, NOT brushless, fan/blower the voltage could be reversed to reverse direction. Second, continuing to blow the air downward would work just as well.

And yes, I used a low side pressure guage to verify my position. With the evaporator "fully" chilled, and as long as it remains so (no airflow), the inlet expansion valve will remain fully closed. No "relief" for the high side pressure as rising engine heat causes it to rise higher and higher.

[kuehl]

Originally Posted by wwest

First, with a standard, NOT brushless, fan/blower the voltage could be reversed to reverse direction. Second, continuing to blow the air downward would work just as well.

And yes, I used a low side pressure guage to verify my position. With the evaporator "fully" chilled, and as long as it remains so (no airflow), the inlet expansion valve will remain fully closed. No "relief" for the high side pressure as rising engine heat causes it to rise higher and higher.

Yes, you can reverse the voltage and the motor runs backwards, however the amount of air moving backwards would not be as significant as you would expect because the pitch of the blades needs to be reversed: fan blades are pitched in different directions; look at a puller fan vs. a pusher fan.

Based on your previous study.... "I admit, willingly, that I was surprised to learn(***) that the "expansion" valve in my '88 could/would remained fully closed for such an extended period. Long enough, ~10 minutes, that I gave up on waiting for the low side pressure to rise above 30 PSI. When I went back later and checked the low side pressure was up to ~80 PSI, just as one would expect."

It seems that you did not address what the high side pressure was at static when you started your observation and what the high side pressure was 10 minutes later.. however you can assume it did drop, and if you wait more than 10 minutes the low and high side will be the same pressure. Its simply a matter of time and the clock starts as soon as the compressor stops.

[wwest]

Originally Posted by kuehl

Yes, you can reverse the voltage and the motor runs backwards, however the amount of air moving backwards would not be as significant as you would expect because the pitch of the blades needs to be reversed: fan blades are pitched in different directions; look at a puller fan vs. a pusher fan.

Based on your previous study.... "I admit, willingly, that I was surprised to learn(***) that the "expansion" valve in my '88 could/would remained fully closed for such an extended period. Long enough, ~10 minutes, that I gave up on waiting for the low side pressure to rise above 30 PSI. When I went back later and checked the low side pressure was up to ~80 PSI, just as one would expect."

It seems that you did not address what the high side pressure was at static when you started your observation and what the high side pressure was 10 minutes later.. however you can assume it did drop, and if you wait more than 10 minutes the low and high side will be the same pressure. Its simply a matter of time and the clock starts as soon as the compressor stops.

Many fans have blades that are not "biased" toward one direction vs the other.

I would assume that as long as the low side pressure remains "fixed" at the low point the high side pressure will increase as the condensor becomes heated.

And yes, it is inevitable that the evaporator temperature will rise with time and therefore the high/low side pressures will equalize.

[kuehl]

Originally Posted by wwest

Many fans have blades that are not "biased" toward one direction vs the other.

I would assume that as long as the low side pressure remains "fixed" at the low point the high side pressure will increase as the condensor becomes heated.

And yes, it is inevitable that the evaporator temperature will rise with time and therefore the high/low side pressures will equalize.

Yes. A ceiling fan can move air in both directions. Unfortunately for the average
DIY here he won't be able to find a fan alike what some have tried on their engine
deck lid that will fit and function like you wish. The fan's that have been discussed through out the forum on the 911 engine deck lid are typically designed (pitch) to move air in one direction; you can reverse the power and get some air 'backwards' but not designed to move it effectively like you wish.

I would imagine the litmus-test to your theory as to whether refrigerant gas expands to the degree enough to push out any leak in the system would be to run the system, get the engine hot. Toss on some gauges. Turn the engine off. Start the stop watch. Get out an electronic leak detector and sniff the joints... Have you tried this?