AC question?

[79jasper]

My buddy who does my state inspections in PA, his father used to run a garage, they would occasionally work on AC and there was a "lazy way" his dad would work on his own ac stuff that was R12 originally but needed to be 134a. First jump the low pressure switch and see if the compressor will spin at all, second jam a can in and see if you can get any pressure to read without blatantly leaking out as fast as it's going in to make sure you don't have a legit rust hole. If that works, add ester oil into the system before filling any further to swell the seals up some and put in enough cans to get the ac to operate even if it isn't perfectly efficient. Run it this way for at least an hour so the oil can circulate and get absorbed some near any dry seals. After this, purge the system (I'm not advocating this part or any of it really), the moisture will come out of most of the system if there was any with whatever else was in there. Then add pag oil, only half the amount the system calls for and fill the system with 134a until the compressor stops cycling with the R12 pressure switch, no more than 8 oz after the system stops cycling.

I will admit that though this isn't the "right" way to do this, when I got my first IDI and hadn't learned to do things right yet, I tried this only from knowing about it from a story he had told me about his dad half assing stuff sometimes... and it's the coldest AC I have. Colder than 2 systems I replaced everything and did totally correct. I'm not saying it's because this method is better, but I think something can be said for some of the older ac parts on our truck being more stout and compatible with 134 than we give them credit for sometimes. I think a new clean orifice valve, and a clean system with good working pressure switches is the most important part.

I was flipping through a book to our JD 624 looking up some torque specs and came across the ac section. It has you add a can right off the bat before you start any testing. Even walks you through flow testing the compressor. Found some of it quite interesting.

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[franklin2]

Just adding a can was the old way of doing it. The EPA frowns on that now, so no one is going to officially write that in their books anymore.

I am definitely not an expert. I do have my gas license but that doesn't really mean anything either. Just that I studied and passed a test.

The only thing I worry about is what I heard about the old r12 oil and the PAG oil not liking each other. No real experience either way, but I was told the ester and the old r12 oil don't react to each other, the old r12 will just lay in the system as the ester is the main lubricant in conjunction with the r134a.

And I have also been told that r134a will actually leak right through a hose designed for r12. But through experiences like was mentioned previously, they found out that old r12 hoses that have been in service for years are somehow now resistant and do block and seal off the r134a. All the new hoses you buy for your old truck are now usually r134a rated hose. If you find some NOS r12 hose on ebay, I would not buy it for r134a use.

 

[david85]

The problem with HC-12a is it's flammable. I think it is legal to use in other countries though.

I read up on that and apparently the flash point is so high the risk isn't as big as you might think.

 

[franklin2]

I read up on that and apparently the flash point is so high the risk isn't as big as you might think.

From what I gathered it's propane.

 

[79jasper]

From what I gathered it's propane.

Close enough. You can use straight propane. Lol

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[david85]

From what I gathered it's propane.

It is a mix of propane, isobutane and other additives. Yes, it is flammable but R12 and R134a can also burn under the right conditions (higher head pressure, more heat, oil in the refrigerant is flammable). R134a can also produce some VERY nasty chemicals when burned, so fire isn't the only safety concern.

Yes, there could be some added risk in running HC12 vs R12 but it's not as straight forward as one can burn, while the other can't.

 

[franklin2]

I have never heard of this happening, so I am just talking right now. But if I had a leak of r134a or r12, and it gathered under the hood and was lit off with a spark from something, I am thinking it's not going to blow the hood completely off the hinges like propane would. I am just making that up, I am certain we would have heard about this in the news if it had somewhere.

 

[YJMike92]

This is getting really complicated. It's really really easy.
The original compressor is leaking (not seized no metal in the system)
Flush the system, Replace accumulator, Replace orifice tube, Add PAG oil 46,
Evacuate (vacuum) and charge A/C. I have been doing this professionally for over 40 years and done at least a hundred A/C retrofits. O-ring replacement is optional. Early in the retrofit game hose, pressure switch, and o-ring replacement were supposedly needed. It turns out none of the concerns about the hoses, switches, and o-rings were valid. If any of those components fail it is not because of the 134A, it's because they are old. Here is a link to an inexpensive kit for a 92 F250. I can't vouch for the quality it's just an example. I personally would try to get a Motorcraft compressor.
https://www.rockauto.com/en/moreinfo.php?pk=9820216&cc=1124558&jsn=3592

 

[79jasper]

If any of those components fail it is not because of the 134A, it's because they are old.

So what you're saying is, if it leaks with R134A, it would've leaked R12? Huh, who woulda thunk it... lol

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[YJMike92]

So what you're saying is, if it leaks with R134A, it would've leaked R12? Huh, who woulda thunk it... lol

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That has been my experience, for what it's worth.

 

[david85]

I have never heard of this happening, so I am just talking right now. But if I had a leak of r134a or r12, and it gathered under the hood and was lit off with a spark from something, I am thinking it's not going to blow the hood completely off the hinges like propane would. I am just making that up, I am certain we would have heard about this in the news if it had somewhere.

The LEL limits make that scenario hard to create unless you have a low point underneath the engine bay to catch the heavier gas in a confined space. Otherwise it dissipates too quickly to reach the LEL. Also keep in mind the low total volume of refrigerant compared to say, a propane powered vehicle fuel tank or a BBQ bottle. Even if it does flash, it's not enough to sustain a fire.

From what I understand, R134a is easy and relatively cheap to buy in the states. Up here in canada, not so much, which is why I've opted for the HC12 option.

 

[franklin2]

That is true, I forgot about propane fueled vehicles. I didn't know if propane was heavier than air or not. I know gasoline is, which is why they make you put your gas water heater so high off the ground if it's in a garage, and why they make you step up from a garage into the house, in case your vehicle has a fuel leak.

All this reminds me of a funny story at work. We have house rentals among other things, and I got a complaint that one of the gas stoves was scaring the renters. Went up there and ran into one of them, they said they would try to light one of the top burners, and it would just sit there and tick and not light. They kept messing with it and all of a sudden there was a big boom and the bottom drawer under the oven where you keep your pots and pans stored would fly out and hit them in the shins.

I get to looking at it, most all stoves you can lift the whole top up to clean it. Not this one. Someone had tried and had broken one of the gas lines to the burner. Fixed that and it was ok till next year the same thing happened again. Someone had tried to lift the top again. This time I went and bought some copper line and put a long loop in it so if they did it again, it would have plenty of line and would not break off.

 

[david85]

Hehe, I remember shooting 16oz propane bottles with some buddies few years back. I had to set up a piece of scrap plywood as a wind barrier and made a small fire under the propane bottle (Yes, really). After that, we managed a 66% success rate for ignition. The flash was enough to push over the plywood but most of the danger was from the bottle rocketing over 100' from the blast. Sadly, the fire didn't follow it because the propane gas was too cold and not mixing right. Maybe the bullet hole was too big.

Sorry for the hijack, I'll stop now.

 

[IDIBRONCO]

Maybe a hijack, but it was still a good story.

 

[Booyah45828]

From what I understand, R134a is easy and relatively cheap to buy in the states. Up here in canada, not so much, which is why I've opted for the HC12 option.

Stupid cheap compared to other refrigerants. And it's available for purchase by anybody sitting on the shelf at walmart, hardware stores, parts stores, etc.