Help me decide on the AC system

[davepl]

My truck is in for final tweaking (charge the AC, align the wheels, etc). The HVAC guy is coming in special to do my truck.

When I restored it, I used all brand new pump, condenser, and dryer. I put in all new o-rings. Whatever is in or on the firewall box is factory original still.

I drained most of the oil out of the compressor before installing it but I didn't flush anything. I vacuumed the system down to get moisture out while it sat waiting. The dryer says its compatible with both R-134 and R-12 (I guess they mean the dessicant inside is compatible).

Now: can I have it charged with R-134? Or do additional changes need to be made?

The mechanic (not the HVAC guy) said that you can still get and use R-12 on old vehicles but that it is very expensive. If that's true, perhaps that's the way to go if R-134 requires changes that I haven't yet made.

Is there a short answer on which way and how to proceed from this point to getting it charged and running?

Thanks!
Dave

[87Skier]

I would go with R134. It's a lot cheaper and anybody can service it. Just looking at the prices on Amazon R134 is about $5.50/pound while R12 is about $20/pound. It is slightly less efficient though.

The only changes that your truck might need is to flush the rest of the system (evap and lines), and to make sure that your compressor wasn't filled with mineral oil (R12 only) instead of pag oil (R134a only).

[ERASER5]

Originally Posted by davepl

My truck is in for final tweaking (charge the AC, align the wheels, etc). The HVAC guy is coming in special to do my truck.

When I restored it, I used all brand new pump, condenser, and dryer. I put in all new o-rings. Whatever is in or on the firewall box is factory original still.

I drained most of the oil out of the compressor before installing it but I didn't flush anything. I vacuumed the system down to get moisture out while it sat waiting. The dryer says its compatible with both R-134 and R-12 (I guess they mean the dessicant inside is compatible).

Now: can I have it charged with R-134? Or do additional changes need to be made?

The mechanic (not the HVAC guy) said that you can still get and use R-12 on old vehicles but that it is very expensive. If that's true, perhaps that's the way to go if R-134 requires changes that I haven't yet made.

Is there a short answer on which way and how to proceed from this point to getting it charged and running?

Thanks!
Dave

Technically it's the desiccant bag that is compatible. R134A destroyed the old bags and blew desiccant all through the system.

The expansion valve should be replaced with a unit tuned for R134A. An R12 will work, but it will not be as cold.

R12 expansion valve hold the low side to about 32 to 35 psig and an R134A unit will hold the low side to 20 to 28 psi depending on the type of pump.

The oil must be R134A compatible also. Ford uses PAG oil.

[lutronjim]

Don't know if it is still around, but their was a refrigerant called fr12 which was compatible with r12 and a lot cheaper. Although I'm sure r134 is way to go long term.

[Davidf]

There will be all sorts of different points of view on a/c systems, so here is my point of view... not the only right answer:

R12 vs R134a: R12 is a more efficient refrigerant at shedding latent heat. So, if you switch to R134a, you really should upsize/upgrade the condenser to help the R134a get rid of the heat within the refrigerant. If you don't change out the condenser, it will work, but once you get above about 95 degrees ambient, the cooling performance will start to drop quickly (and compressor head pressure rise quickly).

R12 vs Freeze 12. not even sure you can buy Freeze 12 anymore. you can probably find it on Ebay. But, STAY AWAY from Freeze 12 or any other drop in replacement to R12. The drop-ins contain compounds with different size molecules. It works ok as designed, until the compounds with the small molecules leak out of the system first. Then, you are left with a "refrigerant" that does not work well at all.

The original A6 compressors will work with R134a if in good shape. I would suspect the front seal and be almost assured it will leak. Rebuilt A6 aren't usually any better. Best to replace with new aluminum bodied A6 form factor replacements. New compressors work with either R12 or R134a.

Flush the system: If you did not remove, drain, and clean the evaporator, you need to do a thorough flush BEFORE you put the new compressor in service. You don't know what trash might be in there and you don't want to kill a good compressor. Also, mineral oil and PAG oil are not compatible with each other...they don't mix. Left over mineral oil will park the low spot in the system.

POA valve (throttling suction valve). It should be checked tested to ensure it operates properly (search this site). Most can be adjusted for use with R134a and R12. I cannot remember the pressure values for R134a, but that information can be found easily enough. A well operating valve is crucial to the proper operation of the system. If in doubt buy a rebuilt replacement. Do NOT use the so called "POA update" tube...it sucks (pun intended).

Mineral vs Pag oil: all mineral oils are created equal (as intended for a/c systems that is). However, there are many different viscosities of PAG oils. Be sure to add the proper viscosity PAG oil into whatever compressor you go with if using R134a. The wrong viscosity oil can kill a compressor in short order.

I suggest you stay with R12 if you feel you can afford the refrigerant cost.

[Waldoe]

I agree with davidf. If it were me, I would let the condenser make my decision. If I was going to use the existing condenser, r-12. For the cost of the new condenser and the retrofit for 134a, could just by the r-12, and it will work.

[davepl]

If by condenser we're talking about the heat exchanger in front of the radiator, brand new, and supposedly compatible.

DavidF's concern above about the compressor worries me a bit - when I vacuumed it down I was losing about half the vacuum overnight, so a very slow leak. If it's the compressor seal that might get better under pressure rather than suction, but you never know.

Should I go with R-134, and it leaks (within a week or two), should I expect the shop to be on the hook for that? They're not supposed to fill a leaking system per EPA rules, but you never know with a slow leak.

[Waldoe]

Keep in mind, that I do not do auto a/c, I do residential a/c. I am only familar with the a6 compressor and I put it on mine because that is what I wanted. The previous owner converted to 134a, poa illinminator, chrome compressor, went thru 3 compressors. I would spend some time looking for the leak. yes the condenser is in front of the radiator. What type of condenser did you by? What compressor? poa valve?

[leddzepp]

I will never use 134 in a factory system again. R12 all the way. It is more expensive than 134 but so what? It works, bottom line, and It is what the system was designed for. You charge it once and you are done. With 134 you need to change this and tweak that, swing a dead chicken over your head...and if you are sitting still in traffic at a temp over 80, it will not work. I also went through 4 A6 compressors and they WILL leak at the front seal eventually with 134.

[Waldoe]

Mine also had a leak in it when I replace the a/c parts. Pressurized the system to 100 psi, used a bottle of soap bubbles, found the leak.

[davischevy]

Confused yet Dave?

[71CHEVYSHORTBED402]

Originally Posted by leddzepp

I will never use 134 in a factory system again. R12 all the way. It is more expensive than 134 but so what? It works, bottom line, and It is what the system was designed for. You charge it once and you are done. With 134 you need to change this and tweak that, swing a dead chicken over your head...and if you are sitting still in traffic at a temp over 80, it will not work. I also went through 4 A6 compressors and they WILL leak at the front seal eventually with 134.

That was my first thought. How often you figure you'll recharge the system? In my case, the system will be used sparingly anyway.

[chopnchaneled]

Originally Posted by davischevy

Confused yet Dave?

Dave may not be,But which way is up

[Andy4639]

I've been running 134a now for 10+ years and haven't had any major problems. I had to take it a part when I swapped out the motor to the LS motor and that was 2 years ago with no problems. Mine runs 38*-40* in 90* weather sitting still are moving.
If your system is 134a compatiable and it's done right you will be much better off in the future. I did swap mine completely over to the orffice tube system. Not really big on the POA valve swap.

[Eddie H.]

Originally Posted by leddzepp

I will never use 134 in a factory system again. R12 all the way. It is more expensive than 134 but so what? It works, bottom line, and It is what the system was designed for. You charge it once and you are done. With 134 you need to change this and tweak that, swing a dead chicken over your head...and if you are sitting still in traffic at a temp over 80, it will not work. I also went through 4 A6 compressors and they WILL leak at the front seal eventually with 134.

I agree, (except for the part about the dead chicken. A fake rubber chicken works just as well, and isn't nearly as messy.) Anyway, the last truck I rebuilt, I went back with R12. I don't care if it is more expensive. If it is done right, you only need to charge it once.

[Andy4639]

You charge any kind of AC system once and your done as long as it's done correctly to begin with. So what is your point?

[leddzepp]

The only reason people switch to 134 in a factory system is the cost difference between it and R12. The amount of money (not to mention time) you spend buying on parts to get 134 to work in a factory system is far greater than the cost difference between R12 and 134. Kinda like spending $50 to save $10. At the end of the day, it still won't cool as well as R12 (110 days where I live). If 134 was my goal, I would just yank the factory AC and go with Vintage or Old Air, an entire system designed for it.

[davepl]

Sounds like R12 - I'm retaining all stock equipment, so as long as it doesn't leak it should be good with R12 indefinitely, and it shouldn't leak!

Thanks for all of the input!

[davischevy]

Keep us updated.

[Andy4639]

I understand if the R 12 system is working good to stick with it. That's a no- brainer. The 134 A will cool just as good as the R 12 if the system is done right and the cost is for either system.

Has anyone bought new parts for a 67-72 AC cab lately? I don't think so, so if your starting from scratch the 134-A is the most economical solution for the long run in my book.
The real question here is do you want a true factory looking system that has the R-12 in it are a system that looks factory but running 134-A. Are a after market system for it. I liked the factory look with the mordern touchs, just like the LS motor swap.

[Davidf]

Originally Posted by davepl

Sounds like R12 - I'm retaining all stock equipment, so as long as it doesn't leak it should be good with R12 indefinitely, and it shouldn't leak!

Thanks for all of the input!

If you stay with the A6 compressor, it will most likely leak. I suggest you replace the compressor with a new aluminum bodied direct A6 replacement compressor such as: http://www.autozone.com/cooling-heat...8_575955_3513/. I used this compressor it works perfectly, weighs considerably less, and is probably less of a HP hog.

[ERASER5]

I may be a bit jaded because I used to do design verification tests for Ford compressors. I would change more compressors in a week than any garage tech in 10 years. Multiple thousands of compressor tests and every competitor compressor both fixed and variable. So when I read "this won't work, or this will leak or this won't cool" my eyes roll to the back of my head.

Just like you can't slap an engine together without correctly machined matching parts, or mismatched, or with dirt on them, neither can you slap an AC system together with mismatched, incorrect or dirty parts.

A POA is not and expansion valve. Eliminating a POA does not mean an orifice tube is going to be used.

Not having a clue what condenser out subcool is the biggest reason for failure to make cold air. Secondly in not knowing evap out superheat or suction pressure at evap in.

R134A can easily be set to freezer levels, you just have to know your numbers.

[Eddie H.]

Originally Posted by Davidf

If you stay with the A6 compressor, it will most likely leak. I suggest you replace the compressor with a new aluminum bodied direct A6 replacement compressor such as: http://www.autozone.com/cooling-heat...8_575955_3513/. I used this compressor it works perfectly, weighs considerably less, and is probably less of a HP hog.

I have heard that the new aluminum A6 compressor replacements were a much improved design, but I have had numerous vehicles with the old A6 and only had one front seal leak in many years of operation. I think they got a bad rap due to the poor quality of rebuilt units.

[davepl]

I'm up against a few walls here: oil in the compressor, never flushed the lines, I think I got all of the o-rings but can't be sure, and the compressor is an old original (actually a 'new' rebuilt original from LMC, but how good that is I don't know).

Since I'm using all era-correct hardware, I think I'll stick era-correct R12. Especially the leak thing worries me (smaller molecules?)

But what is this "RED TEK" stuff that claims to be "both":

Amazon.com: RED TEK 12a Refrigerant 20 Lb...
I'd buy a cylinder of R12 and haul it in with me, as $272 doesn't seem bad, but I can't even tell if it's real R12, so likely just leave it up to the HVAC guy to source it.

[Davidf]

That Red Tek 12a is a drop-in replacement which means mixture of different size molecules, I would bet. Stay away from it. If your A6 was rebuilt by a reputable company, give it a try. I had mine rebuilt locally and it leaked out the front seal probably due to a worn shaft. Lost a charge of R12, so decided to go the A6 replacement route...I am happy with that decision.

Eraser5 probably knows his stuff, but his post is probably not very useful. The gist of what he is saying is that R134a conversions are a compromise and probably wont work well. Now, if you get an entire system from someone like Old Air Products or Vintage Air (like I did for my '52 truck) then it will work very well indeed as all components were designed to work together.

I would bet that many A/C shops won't even work on R12 systems anymore. Call around.