SteveG

Last I heard there was NO drop in substitute for R-12. Beware of anything flammable. The cheap ones usu are. 134a and R-12 vary in price, usu not far apart.

I can't remember the Model #. Robinaire makes a charging station with a heater, which is a nice set up. That would be a compromise betw storing/expense of recycling system. With Dwayne's creds providing such good pictorial guides, I'm sure he can befriend someone w/i a reasonable distance who is already set up. A couple pizzas or a contribution to the R-12 fund would be cool. I wish I was in the So Cal vicinity. That would make sense rather than the $$ and storage space drained away.

JHowell37

Dwayne, I mean this in constructive terms. Considering the amount of OCD you put into the most basic procedures, you should consider making the move to R-134a, so you can do a retrofit/conversion write up.

You're probably going to change the expansion valve(s) anyway, right? I bet you'll probably change the drier too. You're going to wind up replacing every o-ring on it, so at that point, it's not much extra work to do the rest of the conversion.

Properly done, you won't notice any difference in cooling capacity. I think dr bob gets temps in the low 20s out the center vent on his. I got 28 on mine last year. That's cold enough to make your hands ache.

dprantl

It's too bad Dwayne doesn't live close to GA. I would be happy to help with a conversion while he documents it.

Dan
'91 928GT S/C 475hp/460lb.ft

dr bob

I see 19º with the freeze switch jumpered, plenty cold enough to freeze fingers to the wheel. The challenge is getting it cold when the car is heat-soaked. For that the R-12 is slightly better. I'm following the suggestion thread on getting the heater valve to stay closed; this should take out a lot of heat-soak concerns.

Overall I'm very happy with the R-134a conversion. That car is leaking about a pound or so a year from the compressor shaft seal. So long as the gas is under $10/lb and readily available, I'm in no hurry to tear into it. I just don't drive the car enough to keep the seal faces lubricated. As the warm days started showing up here in March, I added two lbs of refrigerant and two ounces of oil to the system. Did it withoiut even starting the car. Performance is still great. Good AC is mandatory in a black car in SoCal for most of the year, so keeping the system happy is not a choice. I did the conversion almost eleven years ago now, the spring right after I bought the car.

blown 87

No chit, and I would let him use all the tools and a shop to do it.

wcj928

I finally got the air working on my 1989 after replacing the control unit with a rebuilt one from 928 International and replacing the expansion valve and drier. I am running R-134 and it is now putting out 44 degree air. I do not now if R-12 is much cooler than that.

blown 87

Look at the temp/pressure curve difference between R12 and 134A on a 100 degree day.
There is a reason that systems made for 134a have high pressure cut offs.

I am going to run R12 in my cars as long as I can get it for my cars that came with it.

The bottom line is that 134a works at higher pressures than R12 on hot days and is harder on everything.

PS, the 928 seem to have a big enough condenser to work better in it than some other cars.

dr bob

WCJ, did you do a thorough (like all night with a serious vacuum pump) evacuation on your system before you added the R-134a? Sounds a lot like you have some air left in the system. Plug your gauges in after the car has been sitting overnight. Temp on the low-pressure gauge correspond to ambient temps? That will give you an idea how much capacity is lost. Figure 1.5 to 2.0 times the gauge difference on a hot day.

I'm with Greg on the higher pressures; use the later pressure switch if you are using R-134a so you have high pressure protection too. Note that the pressures are very similar until you get close to 100ºF ambient. Then the R-134a pressure rise steeply. A heat-soaked car has those temps and more, by the way.

Dwayne

Wow....great discussion and info - THANKS!

I didn't know about the pressure difference between R-12 and R-134A - good to know. Also good to know that very low temps are possible with R-134A as dr bob has achieved and that a 134A conversion is possible without a lot of extra work over and above what I've done to maintain Virginia's and California's A/C system.

I wanted to give an update on which way I've decided to go. We do have long, warm summers here with many days of 100 degree temps. California sits out in the sun all day every day. I've always liked R-12 systems - they seem to do a little better here (although I've never really performed a quantitative performance analysis).

Since I have 4 sharks that I want to have top performing A/C systems and I wanted to be environmentally responsible with the R-12, I decided to jump in with both feet and get a used R-12 Recover/Recycle/Recharge unit. I found a Robinair system model 17700 for sale in Las Vegas and drove over to have a look and brought it home ($1000). Original owner, purchased new in the late 1990's for his car restoration business, always maintained, but has not been used for the last 4 years. Not as great a deal as Bill Ball got on his (which was a STEAL!) but I'm very happy with it. I also found a 30# container of R-12 with about 20# of R-12 still in it that looked in great shape. I drove to Garden Grove and picked that up too ($260) just last Sunday. Ordered a new Robinair Filter for the unit and fresh vacuum pump oil. I'll post pics when I get home and can take some (I'm still on travel!)

I'm really looking forward to doing my own R-12 work - the local shop was OK but I was never sure if they took the extra time and effort to do a really top notch job because I really didn't want to leave the car there overnight. Now, I can take my time and do it right - with a lot of practice, of course.

Dan, Blown 87, and JHowell37, THANKS for your confidence and compliments toward me documenting a 134 conversion - maybe someday - but for now it looks like I'll be sticking with R-12.

I'll post some pictures of the unit soon. THANKS!!

wcj928

Dr. Bob it was converted before I bought it. Expansion valve and drier were just replaced. I will check it. I was happy that it started working again. Thanks

blown 87

Good choice IMHO

I would find a refrigerant identifier to test every system I hooked up to, unless I knew for sure what was in it.

I have seen many cars with all kinds of blends and hydrocarbons in them which will ruin a tank of pure r12 if it is recovered.

Dont forget the safety glasses when working on ac systems.

Greg

papatuki

If the system is allowed to leak, fractionization is kind of irrelevant.
If the leak is repaired. What do you need 30 lbs. of r-12 for?
R-414B IS a drop in.

Dwayne

Well, I decided to order a new tank and hoses for the unit and got them installed recently. This weekend, I decided to charge up Virginia. I had replaced all the o-rings in the A/C system under the hood while I was doing the intake refresh a few months ago. Replaced the receiver/drier and expansion valve as well.

In a previous post, I promised I would post a few pics when I got the system ready to use. Here's the unit after I cleaned the dust off.


I bought and installed a new tank and transferred the R-12 from the 30# container to the machine's #50 tank.


Pretty easy...took about 30 minutes and the machine tells how much R-12 was transferred. In this case, 30#. The 30# container was full.


The only hard part in getting the system hooked up to Virginia and ready to use was connecting the blue suction hose to the low pressure line. Not much room to work there and the blasted transmission cooler line is right in the way! But I managed to get it connected.


The the system was completely empty of freon (the PO said the A/C has never worked since they owned the car and I opened the system to replace the receiver/drier, o-rings, and expansion valve), there was no need to recover any remaining R-12 in the system. So, I started off with the vacuum process.


The machine has an automatic 15 minute vacuum cycle where it pulls 30 InHg for 15 minutes then pauses for as long as you like while you wait for signs of leaks.


After the initial 15 minute cycle, I let it sit for 20 minutes and it still had 30 InHg of vacuum. So I started the recharge process. Entered 2.3 pounds for the charge amount (i.e., 37 oz.) and it charged rather quickly. The machine has a oil drain valve for compressor oil that is pulled out of the system during vacuum and the manual recommends replacing the same amount that is removed. Only 1 oz was removed during my vacuum procedure which seemed curious to me. I believe the system holds 8 or 9 oz so I was expecting more.

I did replace the compressor with a factory new compressor that I removed from my "School House" engine. I assumed all the new compressors came with a full dose of oil so I didn't check oil in the new compressor before installing it.

Here's my Newbie question: Does anyone know when you pull 30 InHg vacuum for 20 minutes or more, will all the compressor oil in the system be pulled out?? If so, that would indicate there was no oil in the new compressor - right? In which case, I should fill the system with a full dose of oil - right? THANKS!

bronto

Thanks for the thread Dwayne, very timely for me. Its hot outside today, and I turned AC on for the first time in months... and there's no cold. The Filmore location is pretty close to me, so I'll be calling tomorrow.

dprantl

When you vacuum the A/C system, almost no oil comes out. You are pulling a vacuum but the oil is in liquid form mostly pooled in the compressor and condenser/evaporator. It's freon that carries the oil, not air. If there isn't any freon in there, there is nothing to carry the oil out. I never add any oil because of the vacuum procedure.

Dan
'91 928GT S/C 475hp/460lb.ft