ASSuming the small amount of pressure I found in the Imperial's A/C system is a sign the car will actually hold a charge, what refrigerant should I use?

I have 4 cans of R12. This system holds 4 lbs 6 oz (dual evaporator two row condenser). In the perfect world that's 5 cans. In the real world, I'll never get full cans in there because of equalizing pressure. I could pick up a 5th can off Craigslist for less than $30.

I have 134a readily available and dirt cheap at work. I did convert my 92 D250 but can't get it to hold a charge for very long.

I know a bunch of "drop in" refrigerants are out there, many of them based on butane or other volatile gasses.

I'd sure hate to dump a the R12 in the system and have it blow out through a leak or rupture.


BTW... I brought home a Robinair vacuum pump to pull down what's currently in the system and verify it will hold. Once that's done, I'll try to evacuate the remaining compressor oil and replace it with new stuff.

If it will hold a vacuum, that's a good sign it will hold the freon. From my understanding the old style compressor doesnt pump R136a for long before dying. Since you have the R12 all ready I;d use it, assuming the system will hold a vacuum for 12 hours.

put the can in a bucket of hot water when you install the R-12. I guarante all of it will go in.

Empting the cans is why you charge thru the low side.Thats why it called suction.That being said I changed a bunch to 134 at work.Most there were no problems.I like to change all the O rings I can get to.Than and a new dryer and adding the proper oil.Then with a good machine you can add a partial charge with dye and most now have sealers in them.If no leaks fully charge.I still have a new can of 12 in the garage I had for my 57.I changed it to 134.Ran it for 5 years.It did have a small leak so I added about a pound every spring.Rocky

I would do what you said and put the R-12 in if your system holds the vacuum. That's quick and easy. If the system leaks in the future or does not hold the vacuum then change the system over to 134a. Be sure to change the oil.

I went with the Envirosafe Industrial 12a when I put my Dakota together. Works great, blows mid 30's at the center vent. And it's compatible with all of the oils.

http://autorefrigerants.com/co00033.htm

$180 plus free shipping for the equivelant of 63 lbs of R12 made the choice pretty easy. Yes, it's hydrocarbon based but think about carrying 20 gallons of gas around. I'm not worried about it.

Tech info: http://autorefrigerants.com/Envirotechnical.htm

There is a shop in town that swears by the HC freons and I have replaced many condensors that exploded as a result. Don't use any HC freon!

Pull a good vaccume, if it holds, fill with your R-12. Heating the cans is a good way to get the last little bit out of them. I ususlly dangle them on the ex manifold. Always atatch them to the low side and after the first can is in start it and turn on the compressor so it actually pulls lowest preasure on that low line, then heat the can to get the most out of it.

PS technically the low side is not really a suction, it still will have much higher preasure than the atmosphere, it is just not as high as the high side

Quote:

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Don't use any HC freon

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Freon is a Dupont trademark for chlorofluorocarbon refrigerant.

the vast majority of refrigerants are "HC".

as an example R-12 is dichlorodifluoromethane, methane is a HC (natural gas). r-134a is tetrafluoroethane, ethane is the next heaviest hydrocarbon to methane.

incidentally some of these can thermally decompose into phosgene gas...which just happens to be a chemical weapon

i changed over my 92 dakota a couple of yrs ago,i DID NOT drain out the old oil,just added the new type oil and 134,NO problems,no leaks

Good news. The car appears to have held a vacuum.
Since my gauges only go up and don't have a vacuum scale, I didn't bother with them. I drew a vacuum on the car for 20 minutes this morning. When I got home from work I connected the vacuum pump again. It started working hard immediately. I poked the schrader valve stem on the high side and the vacuum pump rpm shot up.
After drawing a vacuum again I went ahead and connected my gauges to the high side. It drew the needle below zero. I put the pump away but left the gauge on the car. I'll check it in the morning to see if it reads the same.
If so, it's time to change the compressor oil and charge it.