Of course there will be a lot of questions, but let me just say that I'm definitely not the pioneer of R152a conversions in vehicles. R152a has VERY similar properties to r12, and as many of us all know, R134a conversions don't really work as well as most of us wish. So if only there was some sort of refrigerant we could use in our old R12 systems that would work as well as R12 did.
Yes, good ol' electronics dusters. They contain r152a. You're welcome, everyone. I just used R152a today in my 91, and it's working great!
Here's a quick run-down of what to do:
Gather your equipment. You'll need everything pictured. Manifold gauges are pretty much a must. I used R-134 gauges because let's face it, when are you ever going to run into another time when R12 manifold gauges are useful? Get a NEW receiver/dryer, a new orifice tube, an R12 to R134a fitting conversion kit, a multi-pack of HNBR o-rings, 8oz of Ester oil, lots of non-chlorinated brake cleaner, a side can tap, and last but not least, rent or buy a vacuum pump. You'll need a source of compressed air for this job.
Remove all the lines. I started by removing the battery, it makes things easier. I've never seen such an dismal-looking battery tray. I'll fix that later
Take the lines loose at the bottom of the condenser on the passenger's side.
I also removed the compressor to get all the old oil out. When I got the truck, the seller told me he replaced the compressor with a salvage yard unit, but he never charged it. So thankfully, the compressor never ran. Good, because almost every time you have to replace a compressor, you run into what's known as the BLACK DEATH!
Take the line off:
And remove the old receiver/dryer, and the bottom line off the evaporator.
New dryer, bottom line from evaporator:
Now, see the vertical tube sticking out the bottom of the evaporator core? Pull the old orifice tube out (straight up) with a pair of needle nose pliers. This, my friends, is the black death:
The compressor shits this stuff everywhere through the WHOLE system when it goes south. No big deal, a new orifice tube is $1.99, and a new drier is less than $30.
Now, here's why you bought several cans of brake parts cleaner. You're going to have to flush, SEVERAL times, everything. And I mean flush it all. Fill the evaporator, condenser, and all the lines full of brake cleaner, and blow it all out with compressed air. Hopefully, it entrains all the black death and oil out of your system. Do this numerous times.
Once you get every bit of anything in the system out, and it's completely dry and free of any oil or debris, turn the compressor over and spin it several times to get all the old oil out. Spin it backwards and forwards to get everything out. I like to add some oil to the compressor, spin it a few times, then drain it out the same way to sort of flush it out. Don't use brake cleaner on it.
Now, add your required amount of oil to the compressor. Mine was 8oz, others will be different depending on what type of compressor you have.
Install the compressor. Remember the orifice tube? I highlighted the direction it's supposed to go.
Notice, I have clean hands in this picture. Cleanliness is a must for AC systems. Install the orifice tube in the direction shown.
Reconnect all the lines with new HNBR O-rings, and make sure you lubricate them with oil. Reinstall everything, connect it all up!
Remember the vacuum pump? This is important. Vacuuming the system out removes any air bound up in the system. Regular air in refrigerant systems is bad because it's a non-condensable gas. It also boils off any moisture left over. Hook up the vacuum and suck it down to 30"Hg, and let it sit for about 10 minutes. If the vacuum held, continue on. If not, you've got a leak somewhere, and you need to fix it.
Hook up your manifold gauges and shut both valves. Attach the side can tap to the yellow hose. Tap the first can. This is where you BLEED THE HOSE! Once again, non-condensable gasses are trapped in that line, so get it out. You need to loosen the yellow line at the manifold gauges a little until just a tiny bit of refrigerant leaks out. It'll get cold, be careful.
Charge 2 cans, assuming you're using 12oz cans. The first one should go in with the engine off. The vacuum you pulled will draw the refrigerant in pretty easily. The second can will go in with the engine on, AC on (max AC) and the fan on low.
The reason I say 2 cans is simple. The molecular weight of R12 is 120. R152a is 68. A quick calculation, and 2.5lbs turns out to be 22.4oz. So if you use 2 12oz cans, that's 24 oz. Some will get bled out, some will not go in because the can tap is not exactly perfect science. Trust me, you'll get very close.
Looking back, I spent right at $100 for the whole thing. I already had the manifold gauges, but for an extra $50 at harbor freight, you can have your very own set. You'll pay an astronomical amount more than that to have your AC fixed at any garage, I don't care WHERE you go, it'll cost way more. In south Georgia, $150 is worth it for AC, especially if you get stuck in traffic.
I may be forgetting something, so don't think this is the absolute 100% service manual for air conditioning.