Straightening out my A/C

[alfisti]

So now that it will reach a low of 8 degrees tonight, and we in the northeast have had the worst winter in any recent memory, my thoughts have turned to fixing the A/C on the car :-)

it's an '87 Carrera, and in the PPI, my mechanic noted that the compressor spins fine, and visually everything looked OK, but that the refrigerant had leaked out. He warned me that getting it right could cost a couple of thousand dollars.

He also noted that it might just be that if we top it off at the beginning of the summer, it will retain enough refrigerant to work passably. He felt other than the leak, it was likely to work.

So... I am wondering... I know it's good advice to run the A/C periodically when off-season to keep the seals wet, and prevent leaks. I am wondering - by that same logic - does it make sense for me to top off the system NOW? Obviously I don't NEED the A/C.

Interestingly, when I turn it on, it definitely helps clear the windshield. It's blowing DRY air. Also the air it blows is cold, but then again, it's freezing outside...

On a related note, it appears the right-side warp speed heating lever doesn't go down all the way. I noticed that there always seems to be hot air "leaking out" of the vents. I think I will have to deal with this, as the A/C will have enough problems cooling the car... Any thoughts on how I might fix this? Is it possible I need to clean/lube the flapper boxes??

Thanks
-Glenn in the great white North of NJ

[Bob Kontak]

Has your car been switched over to R134? Throw a can in.

Are you willing to do any work yourself on your car?

In my SC there is one main center vent and two wing vents. Nothing touches the windshield from the AC system. Maybe different than the 87?

[wwest]

First and foremost have a technician install a trinary pressure control switch to both protect and control the operation of the A/C compressor.

Wire the extra fan/shutter control switch between ground and pin #1 (***) of your heat controller module. That will result in the cabin heater blower running automatically, helping to COOL the rear lid condenser AND the engine exhaust manifold-heat exchanger, if your roadspeed is consistently low enough that the engine might begin to overheat.

*** in parallel electrically with the engine overheat thermostatic switch.

You can also add a 15 minute TDR, time delay relay, to provide engine (and rear lid A/C condenser ) after-run cooldown capability as Porsche has done with the 964 & 993 series.

[wwest]

Originally Posted by Bob Kontak

Has your car been switched over to R134? Throw a can in.

Are you willing to do any work yourself on your car?

In my SC there is one main center vent and two wing vents. Nothing touches the windshield from the AC system. Maybe different than the 87?

"...Nothing touches the windshield..." Except indirectly,.... Using the A/C to dehumidify the ENTIRE cabin atmosphere will have a definite POSITIVE effect on keeping the windshield clear of condensation.

Not that I would in anyway indorse such use of the A/C.

[Bob Kontak]

Originally Posted by wwest

" Except indirectly

Yep - I read OP's post too quickly.

[alfisti]

Thanks for the quick replies!

Bob - yes it has been converted to r134a. And wwest is correct - just blowing the A/C into the car magically clears the windows, even if the air cannot be directly aimed at the windows. It just works... which makes me wonder - does that mean there is SOME refrigerant in there, and that it is actually working?

Bob, your logic seems to match mine... no harm in throwing a can in there, right?

wwest- I'm not familiar with some of what you are suggesting... but I'm sure my mechanic, Gene from ******** in NJ, is. I'll run it by him when it's time to REALLY deal with this. I'm likely going to need an oil change by the end of the month, and may even have the valve adjustment done (although in the future I hope to do it myself).

Thanks
-Glenn

[alfisti]

p.s. and YES, I am willing to do some work on the car myself. In the past I've done simple things like brakes, oil changes, interior bits, radio installations, etc., but have never got into A/C work. This car LOOKS simple enough that I feel like I can jump into some things I haven't before, though. Famous last words, right? :-)

[Bob Kontak]

Originally Posted by alfisti

does that mean there is SOME refrigerant in there, and that it is actually working?

Without scientific substantiation , I would say yep, it's working. And yep, a can will not hurt. Not more than one as the capacity is something like 30+ oz's. So that's like two 14oz cans and a smidgeon of a third given line loss. Line loss with the stubby hose DIY "regular" guys use will not be over 1 oz.

If you get a set of gauges, it will be more like 2oz per can as the fill hose is way longer.

wwest is big on protecting the system from overpressure when hot. His thoughts are sound but not necessarily a must do tomorrow thing, "specially" in the northeast. He is also big on SPAL electric fans which help cool the rear condenser and improve refrigerant condensing efficiency. He attracts a lot of heat because of his views. Not that he is wrong at all, but because our systems are so wimpy that in genuine hot/humid climates you need some serious help in the form of upgrades. Search previous threads to pick up some of the local color.

That said, my "hangup" is that I am big on you buying a set of el-cheapo gauges at harbor freight and a 30 lb can of R134a at the local parts store for circa $100 and getting down with your bad self.

If you have an air compressor, the freight offers an anemic, but fairly effective vacuum unit to suck out atmosphere from your system before you recharge. It's in the $15 range.

[alfisti]

Thanks Bob. And as far as needing upgrades, I wouldn't be surprised if I did. Notwithstanding the absurd winter we're having this year, we also have the potential to have ridiculous heat waves here in NJ. And I tend to prefer it chilly in the car (and in the house as well)... so I will appreciate any cooling I can get.

That said, my Alfa GTV-6 2.5 had mediocre A/C and I lived with it just fine. I suspect if I can get this car "working" I'll be OK for the most part. Aim both vents at my midsection....

Also my commute has no real traffic, just backroads through cow country, so hopefully keeping the car cool is not an issue.

So far in about 2 months of ownership, getting the engine WARM has been harder. Amazing that after a couple of miles of easy driving, the temp gauge doesn't move much. Have fun with it a bit, and it goes up just fine :-)

Thanks
-Glenn

[RedCoupe]

I recommend reading Griffiths website at Porsche Air Conditioning,Porsche compressor,Porsche condenser,Porshe condensers,Porsche drier,Porsche driers,Porsche evaporator,Porsche evaporators,Porshe barrier hoses,Porsche air conditioning upgrades,Porsche air conditioning updates,Porsche air co. There is some good information there about the 911 a/c system and its challenges. One thing I learned from reading the site is why older 911's that have been converted to 134a leak their refrigerant out more than when they had the old R12 in them. Apparently, 134a slowly seeps out of the old style rubber hoses that were used on the R12 systems, and because 911s have many more feet of rubber hose than the typical front engined car, they are almost certain to leak their refrigerant out unless they the hoses have been changed to the newer style barrier hoses. Griffiths sells complete kits to replace all of the hoses and they are supposed to be within the ability of a DIYer. They also sell upgraded condensers and evaporators, but I'm going to start with replacing the hoses and a new receiver-drier on my car and see how it does.

[jomama]

If you are able to find R12 you will be much better off or a drop in refrigerant . R134A requires that
The oil must be changed to POE oil with little to no mineral oil remaining in sys .if your sys is charged and you add a can if you did not have a leak you will now .more is not better these are a critical charge sys . If you have gauges the low side pressure should be around 40 to 50 lbs your high psi should not exceed 160 psi . All cars now use the ac sys to cool the windshield to ambient outside temp to reduce the dew point temp on the inside of the glass. I have been a refrigeration mech for 30 years I can talk you through repairing your a/c if you need help

[Dan J]

Being in NJ you have a tremendous resource nearby Griffiths engineering
is truly expert in 911 AC, Is it cheap? No Is it worth it?Yes
Give Griff a call

[alfisti]

I didn't even notice they were in NJ. Thanks!

[alfisti]

Joemama, the car has already been "converted" to R134a. I'm not sure how much was touched vs. left as original, but the new valves have been installed.

Thanks
-Glenn

[wwest]

Originally Posted by jomama

If you are able to find R12 you will be much better off or a drop in refrigerant . R134A requires that
The oil must be changed to POE oil with little to no mineral oil remaining in sys .if your sys is charged and you add a can if you did not have a leak you will now .more is not better these are a critical charge sys . If you have gauges the low side pressure should be around 40 to 50 lbs your high psi should not exceed 160 psi .

All cars now use the ac sys to cool the windshield to ambient outside temp to reduce the dew point temp on the inside of the glass.

No, the exact opposite is the case, cooling the interior surface of the windshield will ALWAYS bring that surface even closer to the dewpoint, just as COOLING the A/C evaporator does....

I have been a refrigeration mech for 30 years I can talk you through repairing your a/c if you need help

"Cooling" the windshield, as does most Asian designs (NipponDenso, Denso US) is just incidental, a side effect, of flowing DRY, dehumidified, airflow over the interior surface of the windshield thereby increasing the vapor pressure enough to begin the evaporative process of the condensate "clinging" to the windshield surface.

In point of fact the "current crop", 2012+, of climate control designs, EVEN NipponDenso/Denso US, never makes use of the A/C compressor except for cabin cooling, cool-down.

Use of A/C to defog/demist the windshield, or even prevent or alleviate same, has always been a wildcard, depending strictly on the whims of mother nature, OAT vs Dewpoint spread, and sometimes even with seriously adverse repercussions.

Use HEAT for defogging/demisting the interior surface of the windshield, and then keep the heat level to the windshield slightly elevated to prevent a re-occurrence.

In really cold climates it often helps to lower the windows slightly to help keep the cabin humidity from rising due to human metabolism.

[wwest]

Originally Posted by alfisti

Thanks for the quick replies!

Bob - yes it has been converted to r134a. And wwest is correct - just blowing the A/C into the car magically clears the windows, even if the air cannot be directly aimed at the windows. It just works... which makes me wonder - does that mean there is SOME refrigerant in there, and that it is actually working?

Bob, your logic seems to match mine... no harm in throwing a can in there, right?

wwest- I'm not familiar with some of what you are suggesting... but I'm sure my mechanic, Gene from ******** in NJ, is. I'll run it by him when it's time to REALLY deal with this. I'm likely going to need an oil change by the end of the month, and may even have the valve adjustment done (although in the future I hope to do it myself).

Thanks
-Glenn

The job of the condensors in your A/C is to remove HEAT from the pressurized refrigerant flowing through them, the colder OAT is at the moment the more efficient that process will be, so much so that there is not only a high probability of evaporator freeze up, that in turn may result in SLUGGING at the compressor, liquid refrigerant reaching the compressor inlet valves.

[alfisti]

so wwest- it sounds like you are recommending, don't run the compressor in these temps, as it could result in freezing up?

Thanks
-Glenn

[wwest]

Originally Posted by alfisti

so wwest- it sounds like you are recommending, don't run the compressor in these temps, as it could result in freezing up?

Thanks
-Glenn

Most modern systems have a compressor lockout if the OAT is below ~34F as the A/C is no longer functional for dehumidifying incoming FRESH airflow. Plus the system is now so highly efficient at heat transfer the likelihood of evaporator freeze up is much greater.

Back in the days when we were providing cooling systems for computers we often had to modify the outdoor condenser to reduce its efficiency in cool/cold weather and thereby prevent evaporator freeze up.

[alfisti]

THANK for the help, folks!!!!

[RSTarga]

An earlier 911 without additional condenser capacity will not work as well on r134 as on r12.
Now that you have converted you need to add condensing capacity and proper hoses.. Talk to Griffiths.
Porsche did not go to r134 until 92 or 93 with the 964.