2009 C2S 174K miles

I guess it is about time I am starting to have some system failures... oh well. I was blowing less-cold air for a few months... maybe even last summer. So, how do I diagnose this thing? Can I just charge it myself from a can of fluid from Autozone?

Peace
Bruce in Philly

 

First you need to see if it has freon which requires a set of 134 gauges before anything else. If its full, you have issues elsewhere. If its low, you'll need a sniffer to find the leak should you be ready to repair it. Of course you can add freon to see how long it takes to get low again. Thats up to you. When I had my NSX, I would add a can every 6/8 months.

 

Bruce, get this AC gauge set from Harbor Freight, pop open the frunk amd remove the plastic trim piece to the left of the battery cover (on passenger side). The AC connections are located under the trim piece. https://www.harborfreight.com/ac-r13...set-60806.html. Instructions are included in the gauge set. Buy a couple of cans of R134 and follow directions on reading the gauge pressures. Your ambient temp will determine how much R134 will be nneded to top off the system.
Or follow this Pelican Parts article on recharging with the Interdynamics recharge kit:
https://www.pelicanparts.com/techart...d_Recharge.htm

 

Great stuff... thanx all. I will look at this in a few days. All my tools are packed as I am in transit to atlanta.... folks tell me my tools are likely stolen.... I will read that Pelican article... buy the stuff from hf...

Peace
Bruce in Philly

 

The first thing I'd do is verify that the compressor clutch is engaging when you to run on the A/C. Start the car in Eco mode where it doesn't run the compressor, then while someone inside pushes the auto button with a cold temperature selected, see if the compressor engages. If not, it could be the system is low on refrigerant, could have a bad low pressure switch, a failed compressor relay, etc. The compressor won't engage if the system is low on refrigerant to protect it - that's the purpose of the low pressure switch.

You can't get a good reading on the system pressure unless the compressor is engaged and the engine at 3,000 rpm so you may have to bypass the low pressure switch temporarily when you're ready with the can of refrigerant to recharge it.

 

The refrigerant charge is determined by weight, not by pressure-

Another A/C Thread (Sorry!) :-) - Rennlist - Porsche Discussion Forums

No A/C... - Rennlist - Porsche Discussion Forums

AC compressor replacement? - Rennlist - Porsche Discussion Forums

 

How does hooking up a pressure gauge like an HVAC gauge set or the recharge can with the gauge on it measure weight? How does a low pressure switch cut the power to keep the compressor from cycling based on weight?

 

Bruce has a gen 2 car. Don't these cars have the constant rotation compressor (ie no clutch)?

 

I think the gist of it is that with variable displacement compressors, the pressure varies based on cooling demand. Not like older compressors where they were on or off and when they were on you had, a specified high/low pressures. With this type of system you can just fill the system until you got to a specific high side pressure.

With modern systems, the only way to accurately recharge is to evacuate the system and refill with the specified weight of refrigerant.

 

I had a similar issue... Was looking at compressors but seems the weak spot is under the dash - namely evaporator which is the same as MK4 (Golf/Jetta/Beetle) all necessary parts are around $100, but dash needs to be replaced.

In mean time I just refiled with this and it seems to have fixed the issue (under $50). Will tackle the rest later.

https://shop.wurth.ca/vehicle-repair...ML/892.764003/

 

I put a can of A/C Pro in my 997.1 earlier this summer and it's still blowin' ice cold.

 

Really, no way to shut off the compressor at all with an Eco mode? That seems crazy if that's the case and makes a 4th or 5th item where the 997.1 is better than the 997.2 to counter the 25 or so reasons the .2 is better. Every car I've ever owned runs differently (less power from the increased load and rougher) when the A/C is turned on. I only use A/C when it's really necessary 90 degrees or above and bet I've used it in my 997 only 10% of the total driving time, if that.

 

The Denso compressor on .2 cars is a variable compression electronic controlled wobble plate system. It varies from almost zero up to 100% depending on cooling load. The shaft turns all the time as there is no "old fashioned" magnetic clutch to swing around and engage. This saves weight and is much more energy efficient. Old style (.1) the pump is off (pulley still spinning) or is at 100 % load with clutch engaged, no in between. This is the same type of concept as used in the .2 main oil pump system where it is a electronic controlled (scary) variable pressure and volume based on needs. Old systems have the pump output directly tied to RPM via the connecting chain or gear drive. .2 has the same mechanical drive method, but the gear engagement is varied thus making a true variable system not dependent on just RPM. The newer turbos now include the variable geometry vanes for the same reason, better performance and much more efficient.
Back to the A/C. The .2 cars are much more efficient . For us old school guys, there is a switch on the console that "turns off " the A/C . The shaft is turning ,but no pumping action. In "auto " mode and the temp inside doesn't call for cold air, then the shaft is still turning but there is no pumping load (very little) on the compressor. Hot day and cold air called for, compressor responds with up to 100% compression. As to diagnosing these systems it could be a little tricky compared to the ole timey mag clutch systems. Those are easy with the high and low pressure switches and the easy to see and easy to shunt magnetic clutch and the flow level glass port. I have a .2 car and have not messed with the system at all ,so I have no real useful advice other than to realize that the system is different. Lots of stuff going on here and yes there is a 'nother computer involved in keeping you cool!

 

That's great info. Thanks for the education.

It's also exactly why I've been buying more old cars than new ones and will likely continue that trend. I really have no desire for anything newer than what I already own, which at the "modern" end is 2 05 997s and 1 09 Cayenne. Next would be a 964 Speedster or RUF 993 R-Turbo or similar, but don't have space (or money) for either of those at the time. My latest '81 928 is sharing duty with my '01 GMC Sierra as my general use cars for the time being.

 

Understood completely. (two of my cars have hand cranks in the tool kit) . I am by definition "old school". Having said that, the newer cars are so much fun and stupid fast. All of the systems are complex, but we can and will continue to work on them ourselves. The hard part for us old guys is getting used to the fact that computers are our friend (really?) and they are the modern day "monkey wrenches" for fixing stuff. The fact that these cars have computers watching computers telling other computers what to do and what is wrong is just so new and foreign to many of us. When (and if it works) it works, we can analyze a problem with a keyboard and not get our hands dirty. Old days and we could spend more than a day figuring out an intermittent problem on a 1951 Hudson, losing knuckles in the process. It is a hobby and by definition, still fun.
Keep 'em runnin'!