Attempted R-152a "Duster" A/C Conversion....some advice....

Brain slur.

BS Chemistry, Magna cum Laude, Phi Beta Kappa here.

What's yours?

With all due respect.

Already stated mine. Been doing a/c since 1982. The cap does not hold in refrigerant. Common sense or half a brain is all it takes to know that. To suggest that you "defer to them" you are really saying that tightening the cap keeps the refrigerant in and that I am wrong. You could just say you believe the cap holds it in instead of "refer to them"

Your education has very little to do with the small amount of common sense it takes to rationalize the facts here and come to a conclusion. High side 250 psi. Plastic cap with rubber seal. Hmm.

As I said pull the schrader valve out and install just a cap. You wont get one can in it before it leaks. Bet.

With my reading to do a good working 152a conversion you have to do the same steps as the 134a conversion. Additional reading shows you can actually mix the two gases in certain CLOSED applications even though one runs happy at twice the pressure. Now, as i live in california and there is a huge core charge and CARB AND EPA all over this stuff unlike a few years ago, I green light the idea of topping off a sorta cold 134a system with a duster can. I'd also consider a full working 152a system if the price of 134a continues to rise due to the deposit problem. Now I have a thread about bringing a/c back from the dead assuming nothing on my truck's system is up to par, I think I'm a candidate for any of them.

People in the trade simply wont have the same mentality as they have equipment to do it right or wrong all day long. The rest of us starting from nothing have to buy the new dryer, the gauges, fittings, vacuum etc and unless they are going to service 10 cars in the family to get ROI cutting corner approaches do deserve attention.

Well after careful consideration I decided to have the system evacuated and recharged with r134. I do want to confirm that in the stock r12 system, I should charge approx 24 oz of 134 into it? So two small 12oz cans for the correct amount? I believe others mentioned that being the right amount to add, I just wanted to confirm first. Thank you.

(I did also add an electric auxiliary fan to the condenser and that seems to have improved the cooling drastically, especially at idle. Hopefully when I go back to r134 it will cool just as good as the duster r152 has, and seeing as I will be getting any air out of the system after I have it evacuated, it will cool even better)

Yes, i think that extra condenser fan will help.

You're not likely to get all 24 oz of R134a from two cans into the system, just can't get all in from cans, there will be some loss as some will remain in the cans, and the gauge hoses themselves get purged with refrigerant. So I'd plan to do 2.5 cans, and see what the pressures and cooling performance is.

Make sure to purge the AC gauge hoses too, let a little R134a hiss out of them to purge even the small bit of air from them.

My .02.

Make sure to pull a good vacuum to remove any moisture residing in the system. That otherwise converts to acids that will react with the aluminum and that can't be helpful.

I agree, pull over 29 inches vacuum for 45 minutes. Then close system and see if vacuum holds 15 minutes. Then add 1st can of refrigerant.

At least with R134a or R-12 an AC shop can work on it someday if needed....

Well had the truck evacuated... Held vacuum for 30 min...no leaks detected. Recharged with r134. Approx 25 oz. At idle achieved vent temp of 58 degrees, blower on high and in recirculation mode. While driving seem to get to about 50 degree vent temps before evaporator freeze up switch engages and kills the compressor. So....overall its slightly colder than with the r152 duster. Def better at idle with the new fan installed. I guess this is as cold as I can get the system to work.

The evaporator should not freeze up period. Even if you put a jumper across the low pressure switch it still should not freeze up. Most tool trucks used to sell a jumper made to use on GM cars where the pressure switch is out by the accumulator. It turns the compressor on and keeps it from cycling too fast until you get enough refrigerant in there.

On an older system like this using a different refrigerant than it was meant to have you can disregard the amount it says to put in by weight. Just get the low side to 40 on the scale matching the refrigerant you are using, NOT THE PSI SCALE, and it will blow cold and not freeze up. This is assuming there is nothing clogging the system and the high side does not get too high.

Understand that the basic way an air conditioner works is:

When refrigerant goes from a liquid to a gas (in the expansion valve and evaporator) it rapidly sucks in heat. When refrigerant converts from a gas to a liquid it rapidly releases heat (in the condenser).

The optimum pressure for this conversion is what the expansion valve is designed to get it to. There may actually be a different expansion valve that futs the lines in your vehicle that works better with R-134a.

Did you know that an expansion valve will work if installed backwards? A GM expansion screen will, and a Chrysler block type will not but an actual old school expansion valve will.

Pressure on low side was at or slightly over 40psi....

Quick question...would a bad or clogged expansion valve cause the evaporator core not to hold onto the same level of coldness after and during the times when the compressor kicks off? I still notice the air blowing a lot warmer than it should when the evaporator freeze switch kills the compressor for those 20 seconds. The temps out of vents go up at least 6-7 degrees while the compressor shuts off. Is that normal? I swear every time my little thermometer hits 50 degrees vent temp, the compressor shuts off for 20-30 seconds...seems to do that more than it should...and even.preventing a freeze up, why do my vent temps go up so Much? It's like the evaporator doesn't hold onto the cold.

To add to the question, I do see a thermal sensor with a probe running into the evaporator case...i assume this is the freeze up switch. It has two pigtail wires connected to it. I've unplugged it but compressor won't engage at that point. If I just pull the wires and splice them together , would that be essentially bypassing it?