I have a 1981 that I just received from my grandfather. The car has been sitting since 1990 in the garage. Only 3,000 miles on it, original. The compressor won't even kick on due to the fact that the original coolant is gone. I've seen kits to convert to 134a, but do you really need to spend $1,500 or can you just change a few orifices? Any help would be greatly appreciated.

 

How much you need t spend depends on what parts are good and what needs replacing. Does the system still have some R-12 in it or is it completely empty? A basic conversion isn't that expensive but if the system has been empty and open to the air then there are parts that are going to have to be replaced. If everything still works at a minimum you'll need to flush out the old oil and replace all of the o ring seals.

 

The $1500 is mostly labor. It's mostly hand tolls that you can do yourself. I've converted several cars to R134. The most important issue is the oil. Old R12 mineral oil is not compatible with 134. The more of the old oil you can get out the better it will work. You have to add new oil, in the correct amount. Read up online, there are at least 2 types to choose from.
I would buy a small vacuum pump and gauge set online. The rest is hand tools. You could even have a pro charge it ($100-150) if you do all the mechanical work. Having your own vac pump ($150) will let you know if it is leak free, and you can fix the leaks, before you take it to the pro.
The way I would approach a not-run-in 20 year system: (This is not completely comprehensive...)

• Vacuum test it to see if you have leaky seals or pinholes. Try to find them.
• Use the dye stuff if you need to find leaks.
• Open the system.
• Replace compressor with a new one. Trying to flush the oil out and reuse it is probably not a good idea, but could be done, especially since it is such low mileage..(your call...) Cleaning the old compressor will be tricky, do it off the car, pour solvent, rotate, empty, purge, repeat, ...
• ADD oil to the compressor, seal it up, and put it aside.
• Pull the condensor and flush it with solvents to get out the mineral oil. Then purge the solvents with shop air.
• Keep all open lines sealed with blue painters tape to keep out moisture.
• Optionally replace the condensor with the new style to get more performance.
• Flush the evaporator in the car with solvents. Rig up some hoses etc. As long as it didn't leak earlier, you did vac test didn't you? It's probably not worth pulling it.
• Honestly I have used the official flushing agent, brake clean, acetone, etc. something that evaporates well and leaves no residue.
• Replace the orifice and all rubber o-ring seals.(non-negotiable - need green R134 ones)
• Replace the accumulator. (Non-negotiable - different dessicant R134 pack). (Buy from AC Kits online)
• Need new R134 fittings, (buy good ones online from AC kits or similar, not at auto parts store.)
• Need new R134 pressure switch or a way to adjust the old one.(if present on a vette AC?)
• Then reassemble.
• Add remaining oil to the accumulator.
• Purge the system with shop air, low press., has some moisture so vac pump it out quickly.
• Purge it with a can of 134, pump it out and remove it.
• Vac test again. Make sure it holds for like an hour.
• Then charge it yourself or get a pro to do it.
• You could also pay a pro to flush it, they have specialized equipment for that.
• Easy right? LOL Worth saving $1500 in labor?

 

I was told that the R134 would permeate the R12 hoses. Thus the hoses would need to be changed. Any truth to that?

Craig

 

I converted to 134 about 18 years ago and no hose problems. There is a oil that is compatible with 134 & 12.

Dom

 

Don't know what all my local AC guy did but I didn't replace any hoses or compressor but, I did replace the 'dryer'- added some oil too, replaced the Aluminum tubes/lines w/o-rings and Orifice Tube screen...the R134 he used shows on a temp dial a 40 degrees difference on a VERY hot Day
100 degrees outside, inside measures at the passenger vent 40 degrees colder...I'm a happy camper.
I will at some point need to replace the FAN...and I've read that is a major PITA!

 

If you want to test the compressor, just by-pass the pressure switch on the passenger side inner fender.... Pull the plug off and jumper a wire from one side to the other... this will tell you if the compressor is working, it won't tell you how well it's working but it'll give you a starting point. I've never had to replace the hoses to convert to 134, just be aware that it will cool decently but never as well as r12.

Willcox

 

I upgraded the AC in my 78 this spring with a kit from Original Air Group. All in with shipping and taxes (FL and TX) was around $950. Includes a sanden style compressor and a new condenser. Shop labor was around $500, so your estimate is pretty close .

 

This car literally sat from 1990 until 2015. So far the entire braking system including pads, calipers, and master cylinder has been rebuilt and cleaned. The struts have been replaced. The entire fuel system from the sending unit to the carburetor has either had to be replaced or has been cleaned and rebuilt. I still have the original wheels and tires, but I decided to replace them with aftermarket. I wasn't sure if there were any broken belts in the tires even though there is no dry rot. The water pump just started spewing coolant, so I'm in the process of changing that out. The air conditioning was sort of an afterthought, but eventually this year I'll get into that.

 

 

I moved here about 7 years ago. I'm originally from South Bend.

 

The original tires would be dangerously too old. Toss them.

 

Why convert it? Keep it r12. Change drier, check for leaks, replace hoses as needed. R12 isn't as expensive as it was 10 or 15 years ago. Old systems were designed for r12 .

 

I can't find it anywhere around here. The one person I found that knew a guy that had some was charging $400.

 

I have 4 cans R-12. $25 per can plus shipping.

 

That may technically be true for brand-new R12 hoses, but once the hoses are coated with oil that no longer seems to be a problem.

 

Ester oil is compatible with both R12 and 134A. The problem isn't so much compatibility with the freon used as it is with the two oils, mineral and PAG. although 134A does not carry mineral oil well. Ester oil is compatible with both oils and both refrigerants.
I have use Ester in my 134A converted AC with no issues. Using this oil would eliminate the need to flush the system of all the old mineral oil.
Replacing the filter dryer (accumulator) at this point would be a must however if the system has been empty and breathing. if it's still got freon in it you are in luck and the filter dryer is likely still fine.

If you go as far as opening the system and recharging you may as well increase the efficiency of the orifice tube by using a Ford blue orifice tube (your going to be replacing it anyhow) it's a .67 orifice vs the common .70. using the smaller orifice will create a greater pressure drop making the freon cooler at the evaporator (your ac vents).

Use the original compressor if you can, today's R4 compressors are not of the quality of the older original ones. You will likely need to replace the front seal as it has been drying out for 20 years.That will require at least a puller and installer for the clutch assembly. Can be had for pretty cheap on e-bay.

 

You can get away with not replacing the OE ac lines but they will leak. I guarantee it. The OE hoses are not barrier hoses and the crimp joints at the fittings will also leak.
The R-134a refrigerant molecules are so small they can and do make their way through non barrier lines.
I'm a little confused as to how reducing the amount of refrigerant that can pass into the evaporator core will increase the cooling capacity.
Flushing the system with ac solvent and blowing out with shop air will work fine for cleaning the lines and both the evaporator and condenser cores of old lubricant. If you have a water separator plumbed into you air compressor, yur golden.
Compressed nitrogen is the best practice, but ......
Purging the system with refrigerant after flushing with ac solvent and shop air is a waste of time, effort, and refrigerant, not to mention a violation of EPA regulations.
You need to use whatever oil the compressor manufacturer specifies if you decide to replace the compressor, which would be the best course of action.
A new accumulator and pressure switch are also needed.
2 points here regarding the conversion:
A larger condenser core will help improve the system cooling, but you will have to compensate for the increased internal capacity of the condenser by adding a little extra 134a, how much? That's kind of an educated wag (wild *** guess).
Which leads me to how much R-134a to put into the system after it has been flushed and evacuated. Rule of thumb is 85% by weight of the R-12 charge on the OE data label.
​​​​​For example, say your system uses 3# of R-12, 85% of 3# is 2.55 #.
Kind of difficult to weigh out that amount without a machine, but close enough is usually good enough. Too much or too little refrigerant will cause poor cooling.
If you can find a few lbs of R-12, and your compressor works and doesn't leak, I would recharge your existing system. Or replace the compressor and recharge, since the compressor seals may or may not leak.
Keep in mind, that the system may hold a perfect vacuum, but when charged can leak. Seen it, done it, got the stupid t - shirt to prove it
I've not replaced an accumulator that was not physically damaged. If the system is evacuated for 30-60 minutes the desiccant will dry.
Pulling a good vacuum boils off all water in the system.
Personally, if I had the R-12, I'd keep it R-12.
YMMV

 

Pretty decent explanation of the blue vs the stock orifice tube. Not written by me. Note the bold section.

 

Thank you for that explaination, makes sense to me.