Decent 911 A/C is possible

[RNajarian]

FIRST AND FOREMOST I do not want to start another Pelican A/C brawl.

I am very pleased with my results, there are many different ways to get desirable A/C results, many vendors, many philosophies.

In a nutshell, my 1975S had a dealer installed under dash system installed. The system was removed during the engine swap. In 2013 I completely reinstalled the system adding a front condenser and blower fan. The car has non barrier hoses and all used OEM hardware. In 2 years I have had to add 1/2 a can of R134 due to 1)Hose leakage or 2)Connection leakage 3) or both

On 85 degree (low humidity) Southern California days I can initially get sub freezing temps


After 30 min of freeway driving the temperature rises to 32 degrees



Eventually vent temps riding to high 30s low 40s

Today it was a scorcher in Southern California so I thought I would give my system a real test.

I taped a wireless temperature sensor to the front bumper and took the car out for a spin

Initial temperatures were outside 105 f vent temp 32.9 f



After 30 minutes of freeway driving, indicated outside temp 107, vent temp 42.8 f



For now I will leave well enough alone, but if I ever have to open up the system I will definitely upgrade to newer better designed hardware.

I realize these results would be much different in the humid south. Some of you may notice the thermometer in the ash tray indicates 87 degrees in the interior of the car. During the test I had both windows open 1 inch due to a bad targa seal.

Again I hope this thread does not deteriorate to a hate fest. I just wanted to share the fruit of my 2 year project.

Thanks for listening

[TheSt|G]

Bottom line seems to be, if you want the possibility of functional AC, a coupe would be a good choice.

[RNajarian]

Yes the additional surface area of the glass does increase the cabin temperature.

But it isn't unbearable. Tinted windows would help

[Bob Kontak]

Outstanding write-up. Congratulations. Job well done.

Additionally one of the wrestling points in past AC threads has been sub freezing initial temps and no one has taken it beyond sitting in the garage for metrics. Wonderful job.

Originally Posted by TheSt|G

Bottom line seems to be, if you want the possibility of functional AC, a coupe would be a good choice.

That is a funny joke, Stig. Thanks.

[RNajarian]

Here is my write up from 2013 right after the install

The Reinstallation of a 911S' A/C - A Love Story

[wwest]

Thank you so very, very much.

Was a bit puzzled as to the rise in vent temperature but the open windows probably the cause.

[RNajarian]

Originally Posted by wwest

Thank you so very, very much.

Was a bit puzzled as to the rise in vent temperature but the open windows probably the cause.

Hmm, I thought the rise of vent temp over time would be due to a warmer refrigerant 40 minutes after turning system on vs. the cooler refrigerant immediately after turning the system on.

The open windows merely prevented the cabin from achieving maximum cooling

That is my lay analysis

[wwest]

Originally Posted by RNajarian

Hmm, I thought the rise of vent temp over time would be due to a warmer refrigerant 40 minutes after turning system on vs. the cooler refrigerant immediately after turning the system on.

The open windows merely prevented the cabin from achieving maximum cooling

That is my lay analysis

Driving typically involves sustained higher RPM ranges which should add to condenser efficiency, plus more pump volume, so seemingly the vent temperature should declined or least remained stable.

[RNajarian]

Originally Posted by wwest

Driving typically involves sustained higher RPM ranges which should add to condenser efficiency, plus more pump volume, so seemingly the vent temperature should declined or least remained stable.

Yes perhaps, but in my case I am in the slow lane doing 65 at 2200 rpm (ish).

Perhaps more spirited driving (and engine RPMs) will get me the higher pressure/pump volume

[kuehl]

RNajarian,

Nice write up.

A 10F rise in vent temp could be the evap core is starting to ice "partially", reducing
the effective surface area of the coil.

To take that supposition out of the possibilities, when it happens again quickly
pull over to safe place, leave the system running, pop up the front trunk, pull back the carpet, open the smuggler's box lid and see if the evaporator outlet pipe has iced up.
If so... the easiest quick fix is to turn back the thermostat a few clicks.
The thermostat should turn off the compressor clutch at some point moving CCW,
if it does not, keep turning it to full CCW, if the compressor stays on then its time for
a new thermostat (I just had a client drop off a basket case of parts to put in his car
and his 'new' old stock thermostat was shot; always on. )

[canamfan]

I've always believed/thought A/C in a 911 was "decent",(heck, even darn good at times). I've never been one to delete or remove it if it's there. Thank You for sharing your thoughts on this too

[RNajarian]

Originally Posted by kuehl

RNajarian,

Nice write up.

A 10F rise in vent temp could be the evap core is starting to ice "partially", reducing
the effective surface area of the coil.

To take that supposition out of the possibilities, when it happens again quickly
pull over to safe place, leave the system running, pop up the front trunk, pull back the carpet, open the smuggler's box lid and see if the evaporator outlet pipe has iced up.
If so... the easiest quick fix is to turn back the thermostat a few clicks.
The thermostat should turn off the compressor clutch at some point moving CCW,
if it does not, keep turning it to full CCW, if the compressor stays on then its time for
a new thermostat (I just had a client drop off a basket case of parts to put in his car
and his 'new' old stock thermostat was shot; always on. )

Never thought of doing this, GREAT suggestion!I'll give it a try.

One of the next upgrades I will do is put a more robust fan on the front condenser. The current one puts out 150 CFM, there are several units out there which are more capable than my current one.

Again thanks all for the input

[eastbay]

Your experience and mine are similar. I ended up buying all my own AC tools, pumps and gauges back in the 80s when the 'pros' were worthless at fixing even basic AC issues with the even easier to work with R12. There is so much hysteria surrounding vehicle AC it is ridiculous and even more so with air cooled 911s.

[SilberUrS6]

Originally Posted by RNajarian

Never thought of doing this, GREAT suggestion!

When you have AC questions, kuehl's your guy. Do not pay any attention to wwest.

[RNajarian]

A lot of people have asked me why I did not go out and buy all brand-new hardware when I first reinstalled the system.

The reason I did not was because I was nervous after reading all the negative reviews about the 911 AC system to go out and spend for $5000 on hardware which would give me mediocre results.

So my intent was to install a inexpensive AC system and see if good results were possible.

My lay opinion is that good 911 AC is possible, of course it matters where in the country/world you are located. High humidity areas such as the US South will have different requirements then say the more temperate areas of Canada. This is why some systems may require two front fender mounted condensers and others can get away with simply the one under the front valence. Some systems may require additional cooling through a rear decklid fan.

My hardware is tired, it is old and the design is 30 to 40 years old. The newer hardware have much more efficient designs and much more modern materials. I do plan on replacing my hardware as they fail over the years. But for now I have an adequate system and I'm still figuring out the best way to optimize it. One of the things I did which made a big difference was adjust the rear deck lid to improve the airflow through the rear condenser.

One thing I feel that is very important to note that when I initially reinstalled the system I was very careful to ensure all the hardware was clean and all the connections were airtight I used a new larger receiver dryer and I pulled a vacuum and kept it for over a week to ensure the system integrity.

An additional item I need to do on my car is complete the Targa top and ensure proper sealing of the cab. When I do that it would be curious to see how cool I can get the car on the hot summer days.

The next items I think I will be upgrading on my system is a fan/blower for the front condenser and I know I will need to break open the system and replace the evaporator, schrader valve and thermostat. I just don't really have the stomach for that right now.

In my unprofessional opinion the Bottom line is the 911 is capable of decent AC performance the only caveat is that it is not a one-size-fits-all option. You need to carefully designed your AC system for your car and your climate.

But admittedly it is a fun project to do for us weekend warriors. Thanks to all the Pelicans who have helped me and given me guidance through the years I could not of done it without you

[DRACO A5OG]

Congrats Brother. Yeah. mine works great too thank goodness these past couple of days in L.A. traffic was a killer.

Enjoy Brother! Let me know if I you need a hand sealing the targa, I can lend my un-pro hand :-)

[RNajarian]

Originally Posted by DRACO A5OG

Congrats Brother. Yeah. mine works great too thank goodness these past couple of days in L.A. traffic was a killer.

Enjoy Brother! Let me know if I you need a hand sealing the targa, I can lend my un-pro hand :-)

Thanks Pal, I may just give you a call

[Tippy]

Originally Posted by canamfan

I've always believed/thought A/C in a 911 was "decent",(heck, even darn good at times). I've never been one to delete or remove it if it's there. Thank You for sharing your thoughts on this too

Of course OEM 911 AC is good enough for you! You live in Canada!

Spend some time in South Texas, say July through September, around 5 PM and see if it'll suffice.....

[RNajarian]

Originally Posted by kuehl

RNajarian,

. . . A 10F rise in vent temp could be the evap core is starting to ice "partially", reducing the effective surface area of the coil.

To take that supposition out of the possibilities, when it happens again quickly
pull over to safe place, leave the system running, pop up the front trunk, pull back the carpet, open the smuggler's box lid and see if the evaporator outlet pipe has iced up.
If so... the easiest quick fix is to turn back the thermostat a few clicks.
The thermostat should turn off the compressor clutch at some point moving CCW,
if it does not, keep turning it to full CCW, if the compressor stays on then its time for
a new thermostat (I just had a client drop off a basket case of parts to put in his car
and his 'new' old stock thermostat was shot; always on. )

Another scorcher today in L.A. Took the car for another whirl, temp rose ~10 degrees as before, pulled over as you suggested . . . And voila the outlet pipe was frosty.

Likely on the way to a complete freeze up.

Maybe time for one of these



any one wanna help put it in? 👍

[wwest]

Before you do that how do we make sure your's isn't dirty and crudded up...?

Check through the passenger side inlet?

Post #589

My AC burns me up --- Help!


How do we go about confirming, or not, that the increasing engine/exhaust/catcon heat isn't causing the lost of rear lid condensing efficiency due to IR heating..?