['84 Carrera] A/C re-work for mild climate

[Arne2]

What this thread is - an overview of my personal project to make the A/C in my '84 Carrera Coupe functional and adequate for a mild climate (Western Oregon).

What this thread is NOT - a discussion of different A/C theories, or a review of particular products. I do not plan to name the suppliers of my parts, nor the prices thereof. Others who wish to repair/enhance their A/C will need to consider their climate and cooling needs, do their own research, and make their own decisions on what parts they need and who to buy them from, just as I did.

Also note - this is not intended as a guide to make you happy with your A/C. My expectations/car/climate are probably different than yours, you may need to do much more (or possibly less) to your system, depending on your own expectations/car/climate. I can give advice, but in the end you will again need to make your own decisions.

The subject car - a 1984 911 Carrera sunroof coupe, 158k miles, complete service history since new. Paging through said history, it was obvious that the A/C never held it's refrigerant well, even when new. The first recharge was 15 months after delivery, and it was recharged numerous times after that to the present.

When I bought the car (Oct. 2011), the A/C had a fairly recent charge, and at least some cooling was evident. Due to the late season, I was not able to determine how well it cooled, just that the system did work, and was intact.

But when I tested again in late Spring, given the documented history I was un-surprised to find that the R-12 had once again departed. While there are plenty of people who believe that barrier hoses are not necessary, the fact that the Freon in my car had disappeared while the system was unused over the Winter indicated that my hoses were the problem, as no over-pressure condition can exist when the system is not used. So the first decision was that I would replace all the hoses.

My research indicated that for use with R-134a it would be advisable to increase the capacity/efficiency of both the condensers and the evaporator. But I decided that for my climate, I didn't need to go wild on condenser capacity.

Things I dealt with pre-project - In my mind, the project was to make the refrigeration system work. But there are support and distribution parts of the A/C too, and those should be checked and addressed as necessary. In my car's case, I found that while the fan blower for the front condenser worked, it was quite noisy and possibly slow. After looking it over, I decided to replace the fan motor. The rest of the system seemed to be OK, so I had the remaining ounce or so of Freon scavenged. This served two purposes: one is that simply opening and venting the refrigerant to the atmosphere is irresponsible (and illegal in many locales); and also when a vacuum is pulled you can get an idea of how sealed (or not) the system is. The earlier in the project that you can find possible leaks, the better. In my case, I ended up replacing virtually everything, so the leak question was not all that important, but for many people it will be a valuable check.

What I replaced/upgraded

• All hoses replaced with modern barrier hoses, for the reason stated above.
• Front condenser replaced with a higher capacity serpentine unit.
• Evaporator/expansion valve replaced with serpentine unit.
• Receiver/dryer with desiccant suitable for R-134a, required for this type of job.
• New rear OE-style condenser. Most people wouldn't have needed this, but I retro-fitted a rear wiper to my car, which requires a different condenser for motor/linkage clearance.

What I added

• High/low pressure switch. While there are a few people who say these aren't strictly necessary (including at least one Porsche A/C specialist), my research indicated that it was a good idea, and they are not expensive. Cheap insurance.

What I didn't do

• Replace the compressor - The Nippondenso compressors as used on the '84-89 Carreras are reasonably decent models, and mine appeared to be in fine shape, no leaks or bad seals.
• Add additional condensers - IMO not needed for my climate. If I lived where it was really hot and humid, I would have added at least one.
• Use a sub-cooler instead of a receiver/dryer - Two - no, three reasons, the mild climate thing (don't need maximum cooling), not 100% convinced on the physics of the things, and cost (standard R/D is MUCH cheaper than a sub-cooler).

The work itself was straightforward. The hose replacement was a really dirty job. But still not particularly difficult. The condensers are (more or less) a bolt-on job. Wiring the high-low pressure switch is trivial. The evaporator is a bit messy and tedious, but again, not especially difficult. Do the receiver/dryer last, so as to not leave it open to suck moisture from the atmosphere.

Took the car to an A/C shop, who first verified it was still leak-free, then evacuated and charged while checking the pressures. Real world so far is an ambient-to-cooled delta of 30 degrees or more. Will update the temps as the Summer progresses, but for this climate, that should do the job. And with the new barrier hoses, I shouldn't have to do it again for a LONG time.

[wally509]

Arne,

Great post, thanks! I plan on doing the exact same thing to my '87 except that I will try to re-use the rear condenser, just flushing it out. I have some questions for you (I tried posting the questions on another thread, but all it turned into was bickering about trinary switches and barrier hoses and the questions never got answered).

1. When you replaced the evaporator, were there any additional seals or gaskets necessary to seal or re-seal the smuggler's box that may have been overlooked by the A/C parts vendor?
2. Did you have a hard time finding an A/C shop to charge the system? My regular guy seemed reluctant to get anywhere near something like this because he's paranoid about R12 and R12 oil contamination of his equipment.
3. How did you determine your compressor was okay? Did you actually open it up?

Thanks,
Wally

[wwest]

It might be helpful to tell everyone how dirty (or not) both squirrell cage blower wheel vanes, and housing, were. I couldn't believe mine were still moving air, probably a source of the NOISE from the front blower. Also, if you have pictures taken from the bottom of the evaporator you removed that might be helpful.

To be perfectly fair my front blower was just as NOISY post cleaning and referb. as it was before. Glad I was able to disable it totally in the end.

Only one suggestion comes to mind. If you don't have a "swamp" diode and resistor in parallel with the compressor clutch you might be wise to add one. I read somewhere that they were standard on later models.

[Arne2]

Originally Posted by wally509

I plan on doing the exact same thing to my '87 except that I will try to re-use the rear condenser, just flushing it out.

No reason to replace the rear condenser if it is still intact. I had to replace mine due to the rear wiper addition, otherwise I would have re-used it.

Originally Posted by wally509

When you replaced the evaporator, were there any additional seals or gaskets necessary to seal or re-seal the smuggler's box that may have been overlooked by the A/C parts vendor?

The one I bought was complete enough. They could have been a touch more generous with the tar-cork stuff, but otherwise it was fine.

Originally Posted by wally509

Did you have a hard time finding an A/C shop to charge the system? My regular guy seemed reluctant to get anywhere near something like this because he's paranoid about R12 and R12 oil contamination of his equipment.

I used a local shop that's been doing A/C work since the 50's. They had no concerns.

Originally Posted by wally509

How did you determine your compressor was okay? Did you actually open it up?

No. But since it did work not that long ago, and doesn't either make noises or throw oil on the underside of the decklid, I decided to stick with it. That's a decision that could come back to bite me later, but if I does it will be my own fault.

Originally Posted by wwest

It might be helpful to tell everyone how dirty (or not) both squirrell cage blower wheel vanes, and housing, were.

I was actually quite surprised that mine weren't that bad. In my case the noise from the front blower was the motor itself going bad. It was stiff and rough feeling when spun by hand. Not overly dirty inside. I can't explain that.

[Arne2]

Update after 6+ weeks. Had a bit of a setback early. I noticed that it seemed to be cooling less after a couple weeks, and by 4 weeks in, wasn't cooling much at all, even though the compressor was running constantly, not cycling on and off. Took it back to the A/C shop to have them look for a leak.

They used oil with UV dye when they charged it, but could not detect any leaks with the UV lamp. When they hooked up the gauges though, it was obvious that a lot of it had leaked off somewhere. They added more dye, recharged again and asked me to use it a lot for a couple of weeks. Since the first 4 weeks after the first charge was a bit cooler than normal here, they said that it was possible that the R134a was bleeding out of the high side fittings as a gas, not carrying any dye/oil to detect. It was their hope that a leak there might bring some dye with it if I was running the A/C a lot more.

So for the past 2 weeks, I ran the A/C everytime I drove the car, even during the week of rain with temps in the 60's. Just point the vents away and let it run.

Today I took it back in for a recheck. The system is/was still blowing reasonably cold, about 30-40 degrees less than ambient, and the compressor cycles normally. Result of the recheck? No leaks seen via UV, and gauges showed the same pressures as 2 weeks ago after the second recharge.

So far, we can't explain why or where it leaked out the first time, nor why it appears to be fixed now, as nothing has really changed in between. For now, we're considering it to be conditionally good. If in the future I notice lack of cooling or the compressor running all the time, I'll run it back in.

Other issues? Now that I have A/C I can use, I've noticed the evaporator fan blower is a bit noisy, in an odd way. It makes a sort of rhythmic, rattling or chattering sound, but only on speed 2, and only while the compressor is actually running. I'll be looking into that shortly.

Over all results? We all know that the A/C in a stock SC or Carrera is not going to knock your socks off unless it's been seriously enhanced. Since my needs in this climate aren't severe, I didn't do that. And the vent area is obviously lacking in an '84.

That said, I'm pleased that it does work reasonably well—at least for my climate. I can get into the car after it's been sitting all day at work, and it will cool the cabin. Not as fast as a modern car, but it gets the job done.

And it should be quite sufficient to keep the interior temperate while we are out for a day-long drive through the country, since those drives generally start with the interior fairly cool. And that was the goal, after all.

[MConn]

Originally Posted by Arne2

Wiring the high-low pressure switch is trivial.

Arne2,
Just wondering where you installed the pressure switch, and how you routed the wires. If you put the switch at the receiver/dryer, how did you get the wire from the fender well to the frunk?

Mike

[GH85Carrera]

The best place for the pressure switch is on close to the compressor on the line to the rear decklid. You will need to have the line modified with a T do do that.

[Jesse16]

Its interesting to me that will the changes you "did" make, that your delta is still only 30 to 40.
My stock 87 system with new hoses only but with RedTek fluid (propane/butane) does 30 to 35 degrees of delta. No new condensors, evap, or compressor. Also no pressure switches.
My environment isn't too challenging till I drive to South Carolina. I appreciate the info. you posted.

[robhamster]

I recently bought a new line from the compressor to the rear condenser from Griffiths and he installed the switch in the hose right there. I used the clutch power wire to cycle power through the switch and to the compressor. Works great.

[Arne2]

Originally Posted by MConn

Arne2,
Just wondering where you installed the pressure switch, and how you routed the wires. If you put the switch at the receiver/dryer, how did you get the wire from the fender well to the frunk?

I used a T-fitting that attaches to the high-side charge port. Simple, no wire routing issues.

Originally Posted by Jesse16

Its interesting to me that will the changes you "did" make, that your delta is still only 30 to 40.
My stock 87 system with new hoses only but with RedTek fluid (propane/butane) does 30 to 35 degrees of delta. No new condensors, evap, or compressor. Also no pressure switches.
My environment isn't too challenging till I drive to South Carolina. I appreciate the info. you posted.

The propane/butane mixes scare me, from a flammability standpoint. I understand that they are more effective refrigerants than R134a, but not worth the risk to me. Besides the fact they are illegal in many states (including mine).

[dentist90]

Arne, please repost next season to let us know if this charge held. I've had similar experience with undetectable leakage. I had a professional AC shop do a complete recharge a few years ago with 134a (it has been converted). We were good for about 6 weeks.
I've taken matters into my own hands and bought a pressure guage manifold to refill with RedTek. As I am an amateur I wanted to be sure that I didn't overpressurize the system. Last year it took 2 cans (I know... thats a lot eh?) to get the right pressures and cooling effect, but lasted the whole season. This year it took one can. The static pressure was ~50psi (both sides), so it didn't totally leak out. After refill the cold static pressure is 75psi. Operating at 25*C the low side is 35psi and high side is 180-190psi.
I'm waiting to see how this holds. I'm wondering if the 134a leaks out faster than the RedTek 12a, and as my system becomes more 12a based it might hold longer? Anyway, it is only costing me $10/season to stay cool, and that black interior really needs AC some days.

PS: How does one tell if their hoses are barrier type?

[Jesse16]

The Propane/Butane thing is certainly something that gets peoples attention but its such a tiny amount and with no-one scared that flammable gasoline is in circulation around a hot car engine, I see it as simply nothing. Much less actual combustion energy in my tiny amount of Propane vs. 20 gallons off liquid/vaporized gas. No idea how it could be outlawed, its in use everywhere.

[Arne2]

Originally Posted by Jesse16

No idea how it could be outlawed, its in use everywhere.

Many states prohibit the use of flammable refrigerants in automobile air conditioners. Simple as that.

[dentist90]

Originally Posted by Arne2

I used a T-fitting that attaches to the high-side charge port. Simple, no wire routing issues.

Could you post a picture of your installation? I was thinking of adding it inline on the high pressure line next time system is purged. Did you just clip it on the quick release coupler or did you thread it on while the system was discharged?

[Bob Kontak]

Originally Posted by Arne2

Many states prohibit the use of flammable refrigerants in automobile air conditioners. Simple as that.

Arne - I am with you on the flammable stuff. I don't think any state allows it.

May I ask how you determine "real world" temperature difference? I am thinking if you taped a thermometer to the headrest of the passenger seat and you were "only" at 70 degrees in the cabin on a 95 ambient day, that would be pretty awesome regarding comfort for a northern boy.

I did the sanden compressor and barrier hose in the 1990's but still use R12 and I know pretty much how to stay on top of it. My bulkhead vent temps are 55 and it's really not bad in the cabin even with some too-fat seal issues on my Targa (losing anti-therms).

"Not bad" does not count after three hours in 95 degree sun. Gotta drive with the windows down for a bit.

[Arne2]

Originally Posted by dentist90

Could you post a picture of your installation? I was thinking of adding it inline on the high pressure line next time system is purged. Did you just clip it on the quick release coupler or did you thread it on while the system was discharged?

The adapter I used threads on to the original R-12 high side port, and T's to a R134a quick-connect on one leg and to the pressure switch on the other side. I'll try to remember to get a picture of it later tonight after I get home.

Originally Posted by Bob Kontak

May I ask how you determine "real world" temperature difference? I am thinking if you taped a thermometer to the headrest of the passenger seat and you were "only" at 70 degrees in the cabin on a 95 ambient day, that would be pretty awesome regarding comfort for a northern boy.

Similar. Last time I checked it I was getting vent temps in the low 50's when ambient was upper 80's. Mid-to-upper 80's is typical here, 90's are less common. It appears that it can maintain overall cabin temps in the low 70's even on hotter days. Which I'm fine with.

Originally Posted by Bob Kontak

"Not bad" does not count after three hours in 95 degree sun. Gotta drive with the windows down for a bit.

Agreed. Can't have unreasonable expectations.

[brads911sc]

Flammable refrigerants in automobiles are illegal at the federal level. much different than using them in stationary systems. read the snap. This is regulated by the EPA. It is also banned by more than 1/2 the states at the state level.
It also voids 99% of the aftermarket parts warranties. Read the fine print on the enclosed warranty next time you buy a compressor from your local parts house.
I researched this extensively and used r134 instead.

Sounds like you have a great system and made some nice changes... Great write up. May want to consider a new Evap fan if yours is too noisy...

[brads911sc]

Some light reading on the refrigerant question directly from the EPA.

Ten Questions to Ask Before You Purchase An Alternative Refrigerant | Alternatives / SNAP | US EPA

[rokemester]

Hey, finally a reasonable and useful AC thread! Congrats fellow forum members. This is quite useful.

[Arne2]

Originally Posted by brads911sc

May want to consider a new Evap fan if yours is too noisy...

Going to look at the evap fan this weekend. I'm thinking the noise may be from bad install, will see...