Has anyone converted their R12 AC to 134a?

[dan-o]

The shops want big bucks to convert my air conditioner from R12. How do you get all the old oil out of the system? How much do you put back in? How much vacuum do you pull on the system? Etc.
Any information or experience would be appreciated. Thanks!

 

[TNBrett]

Order your self a new receiver drier, a complete A/C seal kit, some conversion fittings and a bottle of Pag 46 oil from Rockauto or Amazon.

I took everything apart and flushed everything except the compressor and the new drier with denatured alcohol and compressed air. Then reassembled everything with new o-rings and gaskets.

The compressor I just set it upside down, and turned it by hand a few times. I let it drain like that for a few days, because I had the whole front end of my truck apart. The mineral oil that is in it now won’t actually cause any problems with the Pag oil you will be using.

When you go to reassemble everything lube the o rings with a little bit of the Pag oil.

If the conversion fittings you get have valve cores in them(they probably will), you must remove the cores from your original service ports, other wise you will mess up both of them.

Once everything is back together and you’ve double checked yourself, you can get the gauge manifold set up and hook the vacuum pump to the yellow hose. Turn the vacuum pump on, and open up both the high and low side valves. Remember, that some hoses have valves at the service connectors as well. Make sure that the vacuum pulls all the way down to 30 in/hg or so. If it won’t pull that much vacuum, check for leaks. Leave it running like that for 15-20 minutes. This will ensure there is no moisture left in the system. Then close the valves at the manifold, but not the ones at the service connectors, and shut off the vacuum pump. Leave it set like this for 30-45 minutes. If you loose any vacuum in that time, you have a leak, and you need to fix it.

Go ahead and get a tap on a can of r134a and hook it up to the yellow hose. Start the truck, and turn the a/c on. Open the can tap all the way, and slowly open the blue valve. You don’t need to open it all the way, be patient and slowly add the refrigerant. Once the pressure in the system is high enough the compressor will kick on. It will cycle on and off until you get enough refrigerant in the system. Watch your pressures you want to charge it until the low side gets up around 40 psi when the compressor is running. You can google pressure charts for r134a and get a decent idea of where you pressures should be for a given ambient temperature.

Do not open the red valve with the system charged. Especially when you have a can hooked up, it isn’t meant to take that much pressure.

 

[CDX825]

Ive done a couple of trucks now. Its not really hard but you do need a vacuum pump and a set of gauges.

The right way to do it is to open the system and flush out the hoses and evaporator and condenser. You can get AC flush at the auto parts stores. This removes most of the oil and any other junk that might be floating around in the system. You don't want to put any flush through your compressor though. Same for the accumulator which will need replaced anyway. You want to change all the O rings in the system as well. You can get a complete O ring kit from Oreillys and probably most auto parts stores. The factory blue orifice tube will be blue in color and need changed to a red or orange one. Red is the factory color for R134a but Chris142 has mentioned that an Orange one will work as well. Think the Orange gives better cooling at idle and low speeds if I remember right. You need to refill the system with ester oil. R12 uses mineral oil. R134a uses either ester or pag oil but you want to use ester oil because it plays better with any residual oil left in the system. The oil capacity of your truck will be listed under the hood. Pour the new oil into the new accumulator before you install it. You can also put a little bit in the compressor and work it around.

If you have any friends that do HVAC they will have gauges and a vacuum pump that will work. If not some auto parts stores rent them out. You can also buy cheap ones from harbor freight.

There are couple ways to go about vacuuming and charging the system. Being that I do hvac I have a tank of dry nitrogen to pressure test the system. You can use C02 as well. Its not needed but it makes things nice. If not you want to pull a vacuum and close the gauges off and let the system set to see if it leaks down. You only need to pull a vaccum for an hour at most and then let it sit for at least 20 minutes to see if its leaking. If it passes the leak check turn the pump back on for half an hour and charge it. You need less R134a in the system than what it took in R12. 70 to 80 percent of the systems capacity for R12. If you dont have a refrigerant scale the easiest way is to just buy the 12oz cans and a can tap. When you connect the can to the manifold gauge set make sure you purge the hose from the can to the gauges. You dont want to pump a hose full of air into the system you just spent time vacuuming. You will have to do this for every can you use. You will be able to get so much in before you need to start the truck and turn on the AC. With it running open only the low side of the gauges and dump the rest in.

I think that covers most of it but I might have missed something. If you are unsure about anything just ask.

 

[dan-o]

Thanks, guys! Great info...I appreciate it.

 

[gnathv]

If you don’t have access to temp/pressure chart.
Low side will be 1/2 ambient temp and high side will be 2 x ambient temp + 10 this will get you close.

 

[mexicanjoe]

I've had my '89 F-250 converted and it works soooo good! I think part of it is because my fan clutch stays engaged... In the heat of the hottest day I MIGHT get to 180* engine temperature. . I know that the loud fan roar may be annoying but my little truck stays cool. On 100* days Ive seen 40* air from the registers in the cab. Try the above mentioned information and you wont go wrong, go slowly and watch your manifold gauges...... Let us know how it works out!!!!

 

[WAID]

I converted mine a couple of years ago. I don't think the system had worked since around '93. It was easy enough to flush vacuum and fill with the harbor freight stuff I bought. Mine had leaked down and the previous owners(my parents) didn't want to pay to replace anything after a recharge promptly leaked back out. The only leaks near as I could tell where the valve cores.

 

[Steven Sochalski]

I did mine this past fall. I used the harbor freight gauges, harbor freight venturi vacuum pump, ester oil with UV dye and a uv flashlight from ebay. I flushed the lines and condenser with a flush from AutoZone. The evaporator was clogged, got that from ebay, also got the receiver/dryer there. I replaced the orifice tube and the pressure sensor (leaked, discovered with UV). I purchased a rebuild compressor, but after disassembling my old one, I should have rebuilt. I also bought a new o ring kit. Ollie's has the 134a cans for $4.99 locally. I have about 250 in the entire setup.

Today when I was driving in 90 degree plus it made it worth it. Especially when almost all our era truck I saw had windows down.

I'm running an aftermarket aluminum radiator and a HD fan clutch. It was hard to get my temp up to 190 today.

 

[chris142]

As for the oil amount. Add 3.5 oz of oil per pound or r134a. My truck holds 2.75 lbs or r134a. That equals 9.6 oz of oil. I error on the cautious side and put in 10 oz.

 

[franklin2]

You can do what was suggested above. Or you can just go to Walmart and buy the conversion kit. Then go to harbor freight and buy the air operated vacuum pump and the r134a gauge set.

Put the conversion fittings on, and then take the vacuum pump and gauges and pull a vacuum on the system. See how long it holds vacuum to see if you have any major leaks.

If it holds vacuum, get a jumper to jump the low pressure switch, get the compressor running, and then dump the conversion cans into the system. They have a ester oil mixed in the cans which is compatible with the old r12 oil in the system. No need to get all the old r12 oil out unless you want to go to that trouble.

The old r12 hoses after being exposed to the r12 and the r12 oil, become "pickled" and won't leak the r134a. Same with the old o-rings, unless you have a damaged and leaking o-ring.

So you won't get away without spending some money, but it will be a lot cheaper than paying someone else, and you will have some useful tools added to your shop.

harbor freight vacuum pump. https://www.harborfreight.com/air-vacuum-pump-with-r134a-and-r12-connectors-96677.html $17.99

harbor freight gauge set. https://www.harborfreight.com/ac-r134a-manifold-gauge-set-60806.html?_br_psugg_q=r134a $62.99

 

[IDIBRONCO]

So you won't get away without spending some money, but it will be a lot cheaper than paying someone else, and you will have some useful tools added to your shop.

harbor freight vacuum pump. https://www.harborfreight.com/air-vacuum-pump-with-r134a-and-r12-connectors-96677.html $17.99

harbor freight gauge set. https://www.harborfreight.com/ac-r134a-manifold-gauge-set-60806.html?_br_psugg_q=r134a $62.99

If these are decent, I guess I'm heading to harbor freight after the next time I get paid. I know where I could borrow a gauge set, but not the vacuum pump. Since I can buy both for less than $100, I may as well get some for myself and keep them! I do have another truck that will need some A/C work. I'm just not planning to do the whole thing again to another truck this year, but the tools will be ready for next year.

 

[franklin2]

If these are decent, I guess I'm heading to harbor freight after the next time I get paid. I know where I could borrow a gauge set, but not the vacuum pump. Since I can buy both for less than $100, I may as well get some for myself and keep them! I do have another truck that will need some A/C work. I'm just not planning to do the whole thing again to another truck this year, but the tools will be ready for next year.

I bought the gauges there years ago, and I went for the official vacuum pump they sell that plugs into 120v. I have used that vacuum pump for many different vehicles and even a couple of home A/C systems. The important part with those type pumps is to change the oil often.

I have never tried the one I listed, but it has good reviews. And you will need a decent air compressor to run it.

 

[IDIBRONCO]

Although I do have a decent air compressor, I may have to look into the 120v vacuum pump. I like that idea better anyway.

 

[Steven Sochalski]

O rings are cheap and not hard to do. Especially if you don't change them out and lose all the r134 and have to redo it. Mine were certainly not pickled, they were dry and crunchy.

I'm a believer in fixing it right the first time instead of wasting twice the time, plus extra money, even if it's slightly overkill.

 

[chris142]

You can do what was suggested above. Or you can just go to Walmart and buy the conversion kit. Then go to harbor freight and buy the air operated vacuum pump and the r134a gauge set.

Put the conversion fittings on, and then take the vacuum pump and gauges and pull a vacuum on the system. See how long it holds vacuum to see if you have any major leaks.

If it holds vacuum, get a jumper to jump the low pressure switch, get the compressor running, and then dump the conversion cans into the system. They have a ester oil mixed in the cans which is compatible with the old r12 oil in the system. No need to get all the old r12 oil out unless you want to go to that trouble.

The old r12 hoses after being exposed to the r12 and the r12 oil, become "pickled" and won't leak the r134a. Same with the old o-rings, unless you have a damaged and leaking o-ring.

So you won't get away without spending some money, but it will be a lot cheaper than paying someone else, and you will have some useful tools added to your shop.

harbor freight vacuum pump. https://www.harborfreight.com/air-vacuum-pump-with-r134a-and-r12-connectors-96677.html $17.99

harbor freight gauge set. https://www.harborfreight.com/ac-r134a-manifold-gauge-set-60806.html?_br_psugg_q=r134a $62.99

Really need to replace the r12 accumulator too. The r134a will cause the dessicant bag to break and dump all the dessicant into the system.