The A/C stopped blowing cold about 10 years ago, and a R12 recharge only held for 2 years before it was not blowing cold again.
I’m sure the hoses and O-Rings are leaking after 45 years and will need to be replaced.
The system was open to the air for 5 months last year when the engine was out of the car being rebuilt.
The 1975 A6 compressor is squealing, not the belt, so probably the bearings are shot.
I was thinking of replacing the A6 (R12) with the newer S6 (R134a) that is supposed to be a direct replacement for the stock factory A6 compressor.
And replacing the VIR with Classic Auto Air’s VIR Eliminator Upgrade kit part #15-212.
Can I just have the condenser flushed and reuse it?
I am NOT tearing my dash apart again to replace the evaporator/dryer! If that is a must then I’ll do without A/C.

Has anybody done this?

I am not going to rip out the whole system and replace it with something that costs around $1500 because that’s just not worth the expense for using it once or twice a year when the wife is in the car. When I’m alone I just have the T-Tops off and windows down and don’t miss the A/C.

At any rate, I have decided that I am going to remove the compressor and all the hoses as soon as the garage warms up. The belt is already off. That would make it so much easier to get at the spark plugs.

TIA, Ken

 

Yes, I did mine this past fall... and used the VIR eliminator kit which included a new Sanden compressor from CAA in Florida.

The original condenser will work but is not efficient with the R134, I didn't change mine either but suspect it would work better
with the R134 style condenser.

I didn't really want to remove my dash again either, but in retrospect, I kinda' wish I had just replaced the whole system with a kit from
Vintage Air or the likes. More labor to install but likely would be a better outcome rather than retrofitting and antiquated R12 system that
was designed 45 years ago.

Mine is blowing cool air at around 50ish degrees at this point... the real test will come in a few months when things start to heat up around here again.

mardyn

 

Thanks, If I could get 50 degress on a 90 degree day, I'd be happy. Why? Because the wife would be happy!

If I had a time machine and could travel back in time to this point in my restoration then I would do the whole system.
My back still hates me for this!

 

Get a new r134a condenser or you won't be cooling very well. The factory r12 condenser has smaller orifices as needed for r12 refrigerant but the r134a needs the larger orifices to circulate properly. I learned this the hard way with my 76.

 

Thanks
I was afraid of that.
I just had the hood off and the radiator/condenser moved out of the way for the engine removal last summer.
Did not want to do that again because I actually wanted to DRIVE the car this summer instead of always working on it.
Maybe I'll just tell the wife it's too expensive and keep putting it off..... What will be worse listening to her complain or the couple of times it's really hot around here?

 

The Condenser isn't that hard to remove. Yes it's some work and kind of a bi!@)(, but maybe time well spent if yer going to do the job. One good reason is, you want to make sure there isn't residual (incompatible) oil at the bottom, which is hard to otherwise remove or flush out w/o draining. At the minimum I'd want to remove and ensure it was drained and then double-flushed with solvent. At that point may be best to buy the 'right' one for a 134 system.

The Evap, ...you gotta make sure its flushed out really well. More than you'd think. There's a flushing solvent for that as I'm sure you know. Since you have some time between now and summer, I would advocate a flush of the evaporator, then let it sit a couple days for the chemicals to evaporate and any residual oils to drain down to the bottom inside the evaporator, then perform a second flush with new solvent. B/c it's hard to get all the old oils (incompatible) out on one shot.

Temps: 50 degrees discharge on a hot day might seem ok, but it might hurt more than it helps. The Evap coil needs to get cold enough so air traveling through it condenses the moisture onto the evap coil ...and remove some moisture ....which is the secondary job or an A/C system. The air leaving the coil should have less humidity than air entering the coil. After a few minutes of continued re-circulation, the humidity lowers and lowers again with each pass through the evap coil allowing your wife to 'feel' a lot more comfortable (not just 'cooler') bc you've lowered the amount of moisture in the air (lowered the RH). And in OH you get a number of hot and humid days in the summer, so lowering the RH is critical to feeling 'comfortable'.

Caution: NOT removing the humidity can produce what people in the HVAC industry call "the basement effect". Basically keeping the environment at a lower temperature which allows the relative humidity to rise, making the environment feel dank and uncomfortable. The system has reduced the air temp but hasn't removed much moisture which INCREASES the relative humidity (RH). It can actually feel more uncomfortable. For example, on a 90* somewhat humid day the outside RH could be ~ 60%. You get in and an inefficienty ac system slowly drives the inside car temp down to 75* but in this example hasn't gotten cold enough to remove much water vapor from the air (b/c the AC coil didn't get cold enough). In such a condition the inside RH can climb to ~72% (tropical feeling), which could feel more miserable than perhaps driving with the windows rolled down.

Summary: The above are round numbers for use as an example. The point is, you'll get a lot better results having the 'right' components in place so the AC evap coil will get cold enough to remove water molecules and pull out moisture as well as lower temps. Hope it helps.

Best of luck.

.

 

I agree... I wish they had indicated the need for a different condenser during the initial process of the purchasing the VIR Eliminator kit... I think that would
add about another 300.00 to the kit get close to $1000.00 total.

At that point the decision to purchase a complete after market A/C kit (including a new condenser)
would have definitely be on the table for me.

For now, I'll give the OEM condenser a trial run and see how it does once Spring rolls around here in Texas.

mardyn

 

One thing I did notice on my conversion was that it does make quite a bit of water out of the evap drain... I was kinda' surprised at the amount and even checked to make
sure it was really coming from the A/C case... and it was.

The best temps (at the center vent) I've seen was on test drive to Church about 10:30ish AM before it was too warm outside ... actually saw 44 degree air from the system which felt pretty good after all the effort to make the conversion.

mardyn

 

Mark G:
Good points, with good examples, thanks.
Looks Like if the condenser should come out then I might as well put a new one in.

Mardyn:
You're right about the cost getting close to $1000. Food for thought as they say. But I'm still not tearing that freaking dash apart again.
When my wife drives her Impala during the Summer with the A/C on she's always leaving a trail of water coming up the driveway.

And of course we do get "warm" days in Ohio, but it's the humidity that can really make it uncomfortable.
On the other hand I rarely drive my DD with the A/C on unless I'm on the freeway, I kinda like those 85-90 degree days.

Good points all, THANKS

 

1. R-134a has higher operating pressures than R-12.
2. R-134a molecules are smaller than R-12 molecules and will pass thru the walls of a non-barrier type hose. OE hoses are NOT compatible with R-134a for this reason. Some will say they converted without the hoses and have no problems. The system will work, but it will leak thru the hoses and at the crimps where the fittings are attached.
3. The condenser for R-134a systems is LARGER physically. It has the same size tubes, just more of them. It has NO "orifice size".
3a. Retro fitting can be done using OE condenser, but the system will not be as efficient as it would with the higher capacity of the R-134a condenser.
4. Removal of either the condenser or evaporator core is not necessary. A/C solvent flush is introduced under pressure from a pressurized solvent tank. Then blown out with shop air. Repeat a couple times and the cores will be clean. Any solvent left over will boil out during the evacuation step of the re-charge procedure.
4a. Speaking of the evacuation. Use a good vacuum pump. The system needs to be evacuated for a minimum of 30 minutes. If the system has been open for a while, it would be best if you can let it evacuate for an hour. There is a formula to calculate the required evacuation times, but I dis-remember it right now.
5. A good rule of thumb when converting an R-12 system to R-134a is, re-charge system with 85% of the R-12 charge. easy math here. If your r-12 system used 10lbs of refrigerant, you would only put in 8.5lbs R-134a. I know C-3s' only have a few lbs, but ease of illustration....
5a. If you use the OE condenser, only charge to 85% by weight. If you use an aftermarket condenser that is larger, you will need to add more R-13a due to the increased volume of the condenser. How much more you ask ? That I can't tell you. I make educated guesses and watch the pressure and temperature gauges and see how the system performs. If the system is undercharged or over charged, it will not cool properly.
6. If the system is charged and operating correctly, both R-12 and R-134a systems will have an evaporator core temperature from 35-40 degrees. This is the primary function of the evaporator...to get COLD. The removal of moisture in the air is a secondary effect. Warm air + moisture + cold evaporator = cold dry air + condensate water draining out of the condensate tube. On humid days, water can pour out of the drain tube.
7. Industry standard is 30* reduction of heat from ambient air temp. I.E. If it is 90 outside and you have 60* from the closest duct to the evaporator, the system is operating correctly. 30* reduction - moisture = Happy cold wife. hmm. maybe i should have re-phrased that.
8. Unless your A/C mode is set to recirculate (usually indicated by the "MAX" position), the system draws in outside air, cools, de-humidifies and blows it into the cab, mixing with the warm/humid air already there. When the dry air mixes with the humid air, the relative humidity drops. If you have the system set to "MAX", the A/C system re-circulates air that has already been cooled and dried once, and continues this cycle over and over. Example. If it is 90* ambient, and you are set to "NORMAL" mode, the HVAC pulls in outside air and cools, de-humidifies... and sends it to the cabin. Now you have just cooled 90* air, but it still isn;t comfortable. So you set the controls to "MAX". Now the evaporator is pulling air from inside the cab, cooling de-humidifying, and sending it back into the cab. The air that is being re-circulated gets re-processed and sent out again and again and again.... each time, removing more moisture from the air.

Materials and manufacturing processes have improved, but whether it is an orifice or expansion valve system, they work the same now as they did 60+ yeears ago. The only system that I can recall that has really fallen by the wayside and is considered antiquated, is the suction-throttling valve system that F*rd used to use.


I will say, R-12 systems work better than R-134a systems.

Hope this helps.

Jeff

 

Thanks for all the good information. I can see where only replacing the compresser, VIR, and hoses, is not the best cost effective solution.

I've made a decision for the forseeable future. I cannot afford to drop another $1500-2000 in parts and labor into a A/C repair/upgrade. I just had the engine rebuilt/upgraded last Summer and that blew my budget for awhile.

So I'm just going to stay with removing the belt and any electrical connections and leave the compressor and all the other components installed, as is. This will remove some drag on the water pump and engine. This is a resonable option as it will leave the A/C system intact so that it can be used as a guide at a later date.

Heck, I've been without it for this long that it's not a priority, it's a luxury.

Thanks, Ken

 

I didn’t see recommendations to the type of oils used In the two systems.

R12 uses mineral oil
134a uses PAG oil.
the two oils are not compatible thus all the talk about flushing. However there is a third oil that is compatible with both. Ester oil
use of ester eliminates the need to flush the system of every last drop of mineral oil, as it is compatible with mineral oil.
there is no compatibility issue with the Freon type used just the oils that are used. 134 a and R12 can both use ester oil.
another misconception is that the r12 compressor cannot handle 134a. I’ve been using my r12 compressor with 134a for over 10 years, no issues there.
origional hoses and evaporator and condenser as well.
electric cooling fans help tremendously to increase the efficiency of the condenser.

the secret also lies in the orfice tube size used. I recommend the ford blue. The GM white’s orfice is too large and will not drop the pressure enough to drop the temps. Sufficiently. The ford blue is a little smaller and creates a greater pressure drop through the orfice . The greater the pressure drop the greater the temp drop. There is also a ford red, however it may be too small and create excessive compressor cycling.
blue seems to be a good middle ground for good temp drop and not excessive compressor cycling.

the other side of the coin is good cabin insulation from the engine bay and the outside world. I have additional insulation under the carpet, in the doors and in the t-tops. This helps a lot. Used the bubble wrap foil looking stuff used for water heaters and 3m spray on adhesive.

my a/c in it’s current configuration gets too cold at cruise. I usually have to cycle it off manually since I also have the heater core equipped with valves to isolate its heat from the cabin. If the heater core is supplied water from the engine it creates quite a lot of heat on the passenger side of the car that radiates onto the passengers legs. I block both hoses with valves. This way no hot water gets to the heater core unless I open one valve and if I want hot water to cycle through I open both.

 

My A6 compressor is squealing, and it's not the belt. So that has to be replaced, and from what I've seen it would be cheaper to buy a S6 than to rebuild the A6.
I sure the hoses are leaking because it would not hold a charge for more that 1-1/2 to 2 years before I stopped wasting money on that.

The Oil thing is interesting and something to keep in mind.

Did you keep the VIR? From what I've read, that should be replaced. Is that where you used the Ford Blue orfice?

 

Ken
A few thoughts for you.

I rebuilt the original A6 compressor on my 69. Its not hard and there are great utube vids on how to do it. Basically, you are just resealing everything unless the innards have been destroyed somehow. (About 50 bucks for a complete reseal kit.) I think I spent 2 hours doing it. Disassembly tools from O'Reilly for free.
The squealing is just bearings. New set is easy to find and replace. You will have them off when you reseal the pump anyway.
I bet your original hoses are fine, particularly if you stick with R12. If it takes 2 years before you needed to add freon I don't think the hoses are the problem. It is usually the shaft seal that leaks.
While waiting for summer, why not reseal your A6, new bearings, new receiver/accumulater and find about 5 pounds of R12. (I don't know much about the VIR system. Mine has an expansion valve which I replaced. Old Air has good parts as does Zip.)
Fun tooling around in the heat comfortably in a 50 year old car with the windows up!

Just some ideas for you.
VERYSOON

 

I might just try taking it apart. I probably have all the tools and pullers I need for that job, so it's just time spent to see what it looks like.
But not now. It's in the low 30's out there in the garage and these old bones can't handle that anymore.

Footnote: I just watched a video on pulling apart the A6. It looks like I have all the tools. I like to tinker with taking stuff apart to see how things work so that won't be a waste of time for me,

I see CAA has a VIR Eliminator kit, so maybe that's the orfice change REELAV8R (I assume you are a pilot) was taking about.

 

REELAV8R exactly.
Question. Is the a/c uncomfortably cold? Or is the evaporator freezing up.
From your post, I gather you a familiar with a/c systems.
If the evaporator core is freezing up, maybe install a freeze switch to shut off the compressor when the core gets too cold.
If it is just too cold in the cabin, I got nothing. Lol
Jeff
​​​​​

 

No VIR in my late 77 model it already used an orifice tube.. The VIR replacement kit comes with an orifice tube system to replace the VIR.But it will probably come with the GM white orifice tube.

Any AC system will leak over time with infrequent use. The compressor front seal dries a bit and allows freon by. This is the main reason when you use defrost on your car the A/C compressor is running, keeps the seal lubricated. adding charge every two years is not a serious leak. And if you switch to 134a it'll be cheaper. Learn to use an ac manifold set to monitor pressures. This is ultimately what the system operates on, pressures, not a set amount of freon.

 

No core is not freezing up. It just gets too cold in the cabin at times with the heater core shut off. With it on you can then mix heater air with ac air to get the desired duct temp. I just usually have the heater core shut off.
Original design does just that when selected to max ac, it shuts off the heater core inlet to maximize the cooling in addition to recircing the air. However the heater core is already hot so it takes some time for it to cool. I just prefer to keep it cool for maximum cooling in the cabin.

 

There was no orifice tube in my VIR Eliminator kit from CAA... just a fixed orifice block that replaced the VIR assy.
It seems as the internal valving in the VIR is the main problem when converting to R134 on the early systems and I'm
not exactly sure why other than it was designed for R12 pressures and lubricants.

KenSny... I have a rebuilt A6 style GM A/C compressor from my conversion that I'd like to sell if you're interested... $100.00 to your door.
Keep it in mind.

mardyn

 

I found this thread so while on the subject of AC, I have a few questions. Some may find these stupid, but bear in mind I am not a mechanic and have only owned my 76 for a year. Here in the PNW, the summers are relatively mild since the climate is moderated by the Pacific Ocean, which is only 50 miles to the west of here. Temps. rarely exceed 90, and the humidity is nothing compared to the Midwest and South. I only drive my car when the sun is out, and if the temps. climb, I pop the T tops off. So here goes. Would it be stupid to remove the AC? Why you ask. Well, I don't really use it; never have. It takes up room in the engine bay and inhibits access to other parts like plugs.If the answer is no, can it just be unbolted, taken out, and hoses reconnected. Absolutely do not want the dash out again. Did that last summer to have the heater core replaced. I assume AC would increase the value of the car, but I really have no intention of selling it. In fact, I would like to pass this car on to my son in a few years when I go **** up.Is this reasonable or just leave well enough alone and not create a big headache? Thanks for any insights.