A/C guages -what is needed
 

I am about to embark on the dreaded A/C system changeover and would like to be able to do the job correctly. What guages do I need to use and do I need a vacuum pump ? Anything else that I need other than time, effort and energy. Your thoughts and comments will be greatly appreciated..Thanks !

huh? the 911 is not equipped with an air conditioning gauge. in fact, i've never seen a car with such an instrument.

"changeover" I assume you mean convert to R134, correct?

If so you can rent the gauge for free at a FLAPS. Maybe the vacuum as well. Buy a NSF Food Grade Thermometer Probe. Infrared is good but you really do not want to measure the temp of the plastic, only the air.

WYAIT, I would change out to new valve stems, mine leak and would change if I had to redo my vacuum and fill.

This is the chart you need: http://www.ackits.com/aacf/ptchart.cfm

That's it.

He means "gauges" to take readings for the Hi-Lo side on the compressor. At least that was my read on it. SmileWavy

You need a standard manifold set that has couplers for your chosen conversion. Like this:

89661-PRO gauge set w/manual valves, univ side can tap and plastic case

That set is for 134, however the ends can be switched out to do r12. And yes a good vacuum pump is really key.

nice little mastercool unit here, but there are tons to pick from.

Mastercool 3cfm Vacuum Pump

there's a whole lot more to converting an r12 system to r134 than just filling and reading the pressure. the oils are incompatible, so you need to completely evacuate the old system. the fact that the old system doesn't work (blow cold) does not mean it is completely evacuated. next you need to replace all the o-rings in the system. if the old system is empty because it leaked, you need to fix the leak. next you need to replace all the hoses. a 911 has over 40 feet of them. r12 hoses are porous when used with r134, and r134 will leak straight out through them. you need r134 barrier hoses. then you need to toss that small r12 condenser in the trash, because it's way too small to work with r134. all things being equal, r134 requires significantly more condenser surface area than r12, to provide the same level of cooling. then you need to replace the receiver/dryer with one that has the correct desiccant type for r134. if you have an SC or earlier, then you need to replace the old inefficient compressor with a rotary type (84+ Carrera already has a rotary type compressor).

the only way to do this is the right way, anything else is going to result in a hot and uncomfortable car that doesn't cool well at all and leaks all the refrigerant out over just a few months. The Right Way costs several thousand dollars, which is why most don't bother. but if you try and take short cuts and do it on the cheap, you'll have thrown your money in the trash as the performance will be very poor indeed and you won't be satisfied with it.

My Plan
 

Guys, I plan to totally re-do the system...new compressor, new condensers, new evaporator, new drier, new hoses. new dash vents... In other words....pull out the old and replace with the new.......QUESTION..stick with R-12 or the green stuff or go to R134A ?

R134a is cheap and readily available. Damn if new you should be just fine.

R12 almost impossible without a license. R12 compatible is available like R134.

I use ES-12a in my OEM system, very happy with it and works with either types. Be warned ES-12a is HC but has a high ignition point. Been using the past 3-4 years. No issues or explosions :D

Jim

Guys,

I have read extensively about the different new systems - Kuehl - Rennair - Retro - Sounds like Kuehl has the best directions - Rennair has the procooler and Retro has the best price for basically the same type systems.

If the new systems do not leak down like the old, would I be better served just having an A/C shop do the initial evacuation and also the vacuum and new fill ? Spend the money on other pieces of the system ? Never having done this before, I have no idea what a shop would charge for the above ...Geoff

I just put in a retroaire system, did the charging myself. I bought the manifold/guage set from Napa along with a 1.5 cfm vacuum pump and the r134a.

I figured my pump was a bit weak so I ran it for 12 hours and then let it sit overnight before charging. I probably overcharged a bit (does not take much refrigerant actually for Retroaire....I think 27 oz imho)

The actual charging was not a big deal though....main thing I missed was that the quick connects did not work because you have to remove the schrader valve stems out of the compressor before you put on the quick connects.....once I was told that it made sense, but by that time the system was charged.

I can post pics if you like....I am getting about 38 degree air in traffic.

D.

Cloggie: I would be very interested in pics and your experience in dealing with Retoraire, how the part quality was, etc.

Also, please put your name and model of car in your forum signature...;)

Thanks!

Love to see pics as I am thinking of dealing with Rock at Retroaire

actually it is a big deal. you have to be very precise in your filling and measurement. more is most definitely not better! if you over-fill the system by just 10%, cooling efficiency drops by 40%. in other words, too little is way better than too much.

+1, I agree totally. Recenlty topped off my system and only had one can so I could only fill 80% of the above chart.

Still got 45 degrees, my buddy with R134a, over filled it started to blow out warm air. I tried to explain to him to reduce but stubborn him did not listen and now sweating away.

Have a professional A/C shop convert to r134, <$200. It wouldn't hurt to add a hi/lo pressure switch <$20, and maybe two electric radiator fans to move more air through the rear condensor when the engine is idling and the A/C clutch is engaged.

Spend that ~$300 and then decide if you still need to spent thousands.

Thanks for the tip wwest.....The PO never used the sytem and since MOllY as been with a Porsche mechanic basically since I have owned her, I do not know what to expect. The compressor is not seized as it turns freely on the belt. Once I get her back from her lengthy sojourn, then I can scope out the A/C needs as Albuquerque is quite hot for a few more months and I really want to drive her and show her I am a good owner :=).

Hi again guys,

Yes, charging the system has its challenges and I would definitely agree that the way to go is to put in the minimum amount and then gradually add small amounts (say 2 oz) at a time and give the system plenty of time to settle. If were to do it again, I would get close just in the garage (say if the recommended amount was 27 oz, then put in something like 24, check the pressures and if they are good then run a temperature check by driving around for a while....

If the temperatures are what you want, then stop, if not..then add the 2 oz and repeat.

In terms of Retroaire, yes the instructions are sort of sketchy but I given some feedback that hopefully willl be included. What changed me to using the Retro system is that the car did not have AC, I did not like the multiple condenser idea and definitely did not like the "behind the rear wheel" condenser. I know it works but for my warped sense of engineering, it felt "inelegant".

The Retro condenser was a reasonably good fit, I had to custom make a bunch of stuff as I have an aftermarket duckbill and it most definitely did not have AC in mind.

I ended up crafting my own console even though Retro provided an equivalent of the under the dashpad version from the '70's, I''l try and attach some pictures next.

Evaporator assembly was just fine, but if you have an original one I would use it...I like the fan as it is powerful and not too terribly noisy.

D.

Here is the console I fabbed up from an original SC. The wiring is while I was still in progress....

http://forums.pelicanparts.com/uploa...1311301780.jpg

Vents are from the end vents of the post-'85 cars with a bit of tin. Ducting to this has a "Y" that splits it to go 2 1/2 inch to this console and then 1.5 inch to the centre vent.

Here is the condenser finished before replacing the engine cover. Note that I had to cut the middle support strut, fab a metal support and fibreglas it to the cover. The other supports are just aluminium stock and pop rivets. I know that it allows air to "leak" by, but it does not seem to affect performance. The condenser is all aluminium and quite light ( a few pounds at most).


http://forums.pelicanparts.com/uploa...1311302216.jpg


Douwe

Here is the console again, bit better pic...note the temperature switch and fan blower switch in the fog light and cigarette lighter position. Knobs are from the later 911, I am looking for a pair of old style knobs if anyone has a set to send my way....http://forums.pelicanparts.com/uploa...1311302424.jpg

Douwe